Oil Specialist Reviews Reasons Top 40 Reasons For Engine - Motor Oil Consumption
Description: REASONS FOR
MOTOR OIL CONSUMPTION provides explanations for using “too much”
oil. It serves as a handy reference when the question of “abnormal” oil usage
It is interesting to note that only two oil
related problems contained are explained by “dirty oil” and by overfilling the
crankcase. The balance of the problems is all
mechanical in nature.
Before we review the reasons why oil
consumption occurs, it should be noted that a degree of consumption should be
anticipated in all engines. What is considered normal or acceptable, however,
will vary from one engine or application to the next. For example, Ford Motor
Company considers consumption as high as one quart of oil per 1,000 miles to be
acceptable in a gasoline engine. For large diesel engines used in over the road
trucking applications, many manufacturers are not concerned until consumption
reaches one gallon of oil per 10,000 miles of operation.
External Oil Leaks
Some of the many points where external oil leaks may occur include: oil
lines, crankcase drain plug, oil pan gasket, valve cover gasket, oil pump
gasket, fuel pump gasket, timing case cover and camshaft bearing seal. No
possible source of leakage should be neglected because even a very small link
will cause extremely high oil consumption. For example, it has been estimated
that a leak of one drop of oil every twenty feet is approximately equal to a
loss of one quart of oil every 100 miles. The best way to check for external
leaks is to road test the vehicle with a large piece of light-colored cloth tied
under the engine (caution, keep cloth clear from any moving objects). Oil on
the cloth will indicate a leak which should be traced to its source.
Front or Rear Main Bearing Seals
Worn front or rear main bearing seals almost always result in oil leakage.
This can only be determined when the engine is operated under load conditions.
Bearing seals should be renewed when worn because a slight leak will result in
extremely high oil consumption just as it would with an external oil leak.
Worn or Damaged Main Bearings
Worn or damaged main bearings throw off an excessive amount of oil which
flows along the crankshaft and is thrown up into the cylinders. The amount of
oil thrown off increases rapidly when bearing wear increases. For instance, if
the bearing is designed to have .0015” clearance for proper lubrication and
cooling, the throw off of oil will be normal as long as this clearance is
maintained and the bearing is not damaged in any way. However, when the bearing
clearance increases to .003”, the throw off will be five times normal. If the
clearance is increased to .006”, the throw off will be twenty-five times
normal. When the main bearings throw off too much oil, the cylinders are
usually flooded with more oil than can be controlled by the pistons and rings.
In a conventional, full-pressure lubricated
engine a large loss of oil at the main bearings may starve the downstream
connecting rod bearings of lubrication to such an extent that sometimes,
especially at low speeds; insufficient oil may be thrown on the cylinder walls.
This will cause the pistons and rings to wear to such an extent that they will
not be able to control the oil at high speeds. The effect of main bearing wear
will be high oil consumption.
Worn or Damaged Connecting Rod Bearings
Clearances on connecting rod bearings affect the throw off of oil in the
same proportions as mentioned for main bearings. In addition to this, the oil
is thrown more directly into the cylinders. Worn or damaged connecting rod
bearings flood the cylinders with such a large volume of oil that the pistons
and rings, which are designed to control a normal amount of oil or a reasonable
increase in the normal amount, are overloaded to such an extent that some oil
escapes past them to the combustion chamber and causes high oil consumption.
CAUTION – Insufficient bearing clearance can also produce
piston, ring and cylinder damage as well as damage to the bearing itself.
Worn or Damaged Camshaft Bearings
Camshaft bearings are generally lubricated under pressure and, if the
clearances are too large, excess oil will be thrown off. Large quantities of
oil may flood valve guide and stem areas resulting in increased oil consumption.
Worn Crankshaft Journals
Worn crankshaft journals will have the same effect on oil consumption as
worn bearings. When they are worn out-of-round, they cannot be set up with
round bearings to give uniform oil clearance. A bearing fit to the larger
dimension of a worn journal will be loose at the smaller dimension and throw off
many times the proper amount of oil. Journals which are out-of-round, rough or
scuffed should be reground and fitted with undersized bearings of the correct
Tapered and Out-of-Round Cylinders
In slightly tapered and out-of-round cylinders, the oil can be controlled by
the pistons and rings. However, with increased taper and out-of-roundness,
satisfactory oil control becomes more difficult to maintain. This is due to a
combination of many factors. The increased piston clearances permit the pistons
to rock in the worn cylinders. While tilted momentarily, an abnormally large
volume of oil is permitted to enter on one side of the piston. The rings, also
tilted in the cylinder, permit oil to enter on one side. Upon reversal of the
piston on each stroke, some of this oil is passed into the combustion chamber.
For each revolution of the crankshaft, the
pistons make two strokes – one up and one down. When an engine is running at
3000 R.P.M. (approximately 60 miles per hour) the rings in tapered and
out-of-round cylinders are changing their size and shape 6000 times per minute.
Consequently, at high speeds, the rings may not have time to conform perfectly
to all worn parts of the cylinders on every stroke. Whenever this occurs, the
engine consumes higher amounts of oil due to what is commonly referred to as oil
Cylinders which are distorted so that they are out of shape – not from wear
as in #7, but from other causes such as unequal heat distribution or unequal
tightening of cylinder head bolts – present a surface which the rings may not be
able to follow completely. In this case, there may be areas where the rings
will not remove all of the excess oil. When combustion takes place, this oil
will be burned and cause high oil consumption.
Clogged “PCV” Valve
The main purpose of the PCV (positive crankcase ventilation) valve is to
recirculate blow-by gases back from the crankcase area through the engine to
consume unburned hydrocarbons. Blow by is a mixture of air, gasoline and
combustion gases forced past the rings on the combustion stroke. The PCV system
usually has a tube leading from the crankcase to the carburetor or intake
manifold. Vacuum within the engine intake manifold pulls blow by gases out of
the crankcase into the combustion chamber along with the regular intake of air
A valve can become clogged with sludge and
varnish deposits and trap blow by gases in the crankcase. This degrades the
oil, promoting additional formation of deposit material. If left uncorrected,
the result is plugged oil rings, oil consumption, rapid ring wear due to sludge
buildup, ruptured gaskets and seals due to crankcase pressurization, oil thrown
out around the filler cap and consequent rough engine operation.
10. Honing Abrasive
If cylinder honing or glaze breaking is performed on an engine, cleaning
instructions should be carefully followed to prevent metal fragmentation or
abrasive damage to the rings’ seating surfaces.
Cleaning instructions for reconditioned
cylinders: After honing thoroughly wash cylinder walls with soapy water and a
scrub brush and oil immediately thereafter, or swab cylinders with No. 10 oil
and carefully wipe clean. Repeat until all evidence of foreign matter is
removed. In either method that is used, a white cloth wiped on the surface
should remain clean.
Note: Do not use gasoline or kerosene to clean the cylinder
walls after honing. Solvents of this nature will not remove the grit from the
cylinder wall and often carry particles of abrasives into the pores of the
metal. Failure to properly clean the cylinder walls will leave abrasives that
will cause rapid wear and ring failure and will result in elevated oil
11. Worn Ring Grooves
For piston rings to form a good seal, the sides of the ring grooves must be
true and flat – not flared or shouldered – and the rings must have the correct
side clearance in the grooves. Normally, automotive ring groove side clearance
should not exceed .002-.004. As the pistons move up and down, the rings must
seat on the sides of the grooves in very much the same way that valves must seat
to prevent leakage. New rings in tapered or irregular grooves will not seal
properly and, consequently, oil will pass around behind the rings into the
combustion chamber. Worn grooves are usually flared or tapered causing
increased side clearances which permit more than the normal amount of oil to
pass the rings into the combustion chamber. Excessive side clearances also
create a pounding effect by the rings on the sides of the piston grooves. This
promotes piston groove wear and, if the condition is not corrected, breakage of
rings lands may occur.
12. Cracked or Broken Ring Lands
Cracked or broken ring lands prevent the rings from seating completely on
their sides and cause oil pumping by a process similar to that described in #7.
In addition to this, they also lead to serious damage to the cylinders as well
as complete destruction of the pistons and rings. Cracked or broken ring lands
cannot be corrected by any means other than piston replacement and this should
be done as soon as there is the slightest indication of a crack.
13. Worn Valve Stems and Guides
When wear has taken place on valve stems and valve guides, the vacuum in the
intake manifold will draw oil and oil vapor between the intake valve stems and
guides, into the intake manifold and then into the cylinder where it will be
burned. If this condition is not corrected when new piston rings are installed,
an engine is likely to use more oil than it did before because the new piston
rings will increase the vacuum in the intake manifold. When gum or deposits on
the valve stems are removed – a procedure recommended when overhauling an engine
– the seal previously formed will be removed and leakage will be more
pronounced. This is particularly true on overhead valve engines where loss of
oil may occur on the exhaust valves as well as on the intake valves. High oil
consumption caused by too much valve guide clearance can frequently be cured by
reaming or nerraling the valve stem. In some cases new valves may also be
required. Use of a permanently bonded valve stem seal will give added insurance
against oil leakage on complete engine overhauls or on valve jobs.
14. Bent or Misaligned Connecting Rods
Bent or misaligned connecting rods will not allow the pistons to ride
straight in the cylinders. This will prevent the pistons and rings from forming
a proper seal with the cylinder walls and promote oil consumption. In addition
to this, it is possible that a bearing in a bent rod will not have uniform
clearance on the crankpin. Under these conditions, the bearing will wear
rapidly and throw off an excessive amount of oil into the cylinder.
15. Worn or Improperly Fit Wrist Pins or the Wrong Pins
The use of worn or improperly fitted wrist pins or the installation of the
wrong pins, as in the case of rifle drilled rods where oil is forced to the
wrist pins under pressure, can cause such an excessive throw off of oil onto the
cylinder walls that the piston rings may not be able to control it. This will
not only result in the direct loss of the excess oil but also in the formulation
of carbon which will clog the oil passages and cause the rings to become stuck
in the grooves.
16. Wrist Pins Fit Too Tightly
Wrist pins that are fitted too tightly at both ends prevent the pistons from
expanding and contracting freely under the repeated heating and cooling
encountered in engine operation. The piston distortion results in scuffing and
scoring, which inevitably leads to blow-by and high oil consumption.
17. Clogged Oil Passages
After an engine has had long, hard service the oil passages in piston rings
and pistons will likely become clogged from carbon or an accumulation of foreign
matter in the oil. The passages are designed for carrying oil – in excess of
the amount needed for lubricating the cylinders – back to the crankcase. When
the passages become clogged, oil may be trapped in areas reducing the indicated
level of oil within the engine. It may also pool in areas such as above the
valve guides, which can further promote consumption.
Clogged passages in rifle drilled rods or any
clogged oil line will starve the engine of lubrication, promote wear and lead to
high oil consumption. To avoid clogging of oil passages, the same precaution
should be taken as recommended in #28. Initial side clearance is not applicable
in this case.
18. Unequal Tightening of Main Bearing Bolts or Connecting Rod Bolts
Unequal tightening of main bearing bolts or connecting rod bolts will throw
the bearing bores out-of-round enough to shorten bearing life and to cause an
abnormally large throw off of oil from the bearings. The effect on oil
consumption is described in numbers 3 and 4. When bearing bores are originally
machined, at the time of engine manufacture, the bolts are tightened to the
manufacturer’s torque. A torque wrench must be used to insure roundness of the
bearing bores whenever the bolts are tightened after having been removed and
reinstalled. Unequal tightening of connecting rod bolts may also cause
connecting rod distortion, with results similar to those described in number 14.
19. Unequal Tightening of Cylinder Head Bolts
The strains developed by unequal tightening of cylinder head bolts may cause
serious cylinder distortion and result in oil pumping as mentioned in #7 and
#8. When re-installing a cylinder head, a torque wrench should always be used
on the head bolts. The engine manufacturer’s instructions should be followed
for the torque readings and the sequence in which the bolts are tightened.
20. Dirty Cooling Systems
Rust, scale, sediment or other formations in the water jacket and radiator,
or corrosion of the water distributing tube, will prevent a cooling system from
performing its duties efficiently. This is likely to cause cylinder distortion
with a direct loss of oil as mentioned in #7 and #8.
A defective cooling system causes overheating
of the engine with the possibility of developing localized hot spots in some of
the cylinders. This may also lead to scuffing and scoring of cylinders, pistons
and rings which results in high oil consumption.
21. Dirty Oil
Failure to change the oil at proper intervals or to take proper care of the
oil filter may cause the oil to be so dirty that it will promote clogging of the
oil passages in the piston rings and pistons. This will increase the oil
consumption as described in #17. Dirty oil will also increase the rate of wear
on bearings, cylinders, pistons, and piston rings. All of these worn parts, as
explained in individual items on each part, will contribute to a further waste
Note: as a rule, dirty oil by nature is also consumed at a
higher rate than cleaner oil.
22. Too Much Oil in Crankcase
Due to an error in inserting the oil dip stick so that it does not come to a
seat on its shoulder, a low reading may be obtained. Additional oil may be
added to make the reading appear normal with the stick in this incorrect
position which will actually make the oil level too high. If it gets so high
that the lower ends of the connecting rods touch the oil in a pressure
lubricated engine or the dippers go too deep into the oil in a splash lubricated
engine, excessive quantities of oil will be thrown on the cylinder walls and
some of it will work its way up into the combustion chamber.
23. Incorrect Piston Rings for Type of Engine or Type of Service
If rings of an incorrect size are installed (for instance, .020” oversize
rings in .040” oversize cylinders) they can readily cause oil pumping because
they will not fit the cylinders and will be unable to keep the oil down from the
upper cylinder walls. In this example, ring end gap will also be greater,
resulting in additional oil loss, as described in #26. Different types of
engines and their use in different types of service require individually
engineered ring sets which vary in many ways. Each set has been designed for a
particular purpose, but if one is used in an engine for which it is not
intended, it may be incapable of controlling the oil in that engine. It is
extremely important to always make sure that the correct set is used.
24. High Engine Vacuum
Engine vacuum has increased in modern engines due to the fact that engine
rpm, valve overlap and compression habits have also increased with these
models. Some of the late model engines will draw as high as twenty five inches
of vacuum on deceleration, as compared to twenty inches in older engines. This
high vacuum characteristic has made it necessary for the development of an oil
ring to seal both (top & bottom) sides of the ring grooves and eliminate oil
from passing around the back and sides under high vacuum or deceleration. Such
vacuum could be the main cause of smoking and oil consumption so it is important
that you use a side sealing piston ring when called for.
25. Worn Timing Gears or Chain
Worn timing gears or chain can cause the valves (and sometimes the
distributor) to be out of time with the crankshaft. The large amount of
backlash, which is caused by this wear, will prevent proper engine adjustment
because timing may vary from one revolution of the crankshaft to another. When
the valve and piston motions are not synchronized, extremely high oil
consumption may result. This will be caused by excessive vacuum which draws
large quantities of oil into the combustion chamber where it will be burned.
26. Piston Rings Fit with Too Little End Clearance
When fitting new rings, care must be taken to see that, with the rings in
the smallest part of the cylinder, sufficient end clearance is allowed for
expansion due to heat. Normal gap clearance in automotive engines with cast
iron rings usually runs .003 - .005 per inch of bore diameter. The rings will
heat more rapidly and will operate at a higher temperature than the cylinder
because they are exposed to the direct heat of the burning gases from the
combustion chamber. The cylinder walls are kept at a lower temperature by the
water in the water jacket. This means that the rings expand more than the
cylinder and this expansion must be allowed for by use of a gap – known as end
clearance – between the two ends of each ring. If sufficient end clearance is
not provided, the ends of the rings will butt while the engine is in operation.
Butting will cause scuffing and scoring or
rings and cylinders which leads to oil consumption. If the engine is allowed to
be used for continued operation, especially under heavy load, scoring will
become more severe. The ends of the rings will be forced inward – away from the
cylinder wall – so that a space opens up between the rings and the cylinder.
This provides a direct path for hot gases from the combustion chamber to burn
the oil on the cylinder and greatly increases the oil consumption of the
engine. Severe cases of butting may also cause ring breakage, with the same
results as described in number 27. Excessive ring end clearance leads to
increased oil consumption as well.
27. Worn or Broken Piston rings
When piston rings are broken or are worn to such an extent that the correct
tension and clearances are not maintained, they will allow oil to be drawn into
the combustion chamber on the intake stroke and hot gases of combustion to be
blown down the cylinder past the piston on the power stroke. Both of these
actions will result in burning and carbon buildup on the oil on the cylinders,
pistons and rings.
Broken rings are especially damaging because
their loose pieces with jagged ends are likely to cut into the sides of the
piston grooves. This causes land breakage which results in the complete
destruction of the piston assembly. Instead of reinstalling worn rings during
engine overhaul, it is always advisable to replace them. New rings have
quick-seating surfaces which enable the rings to control oil instantly, unlike
rings which have been used in the past. Used rings, even those that have been
only slightly worn will still have polished surfaces that will not seat-in
properly and will lead to excessive oil consumption.
28. Pistons Rings Stuck in Grooves
Obviously, oil cannot be controlled by piston rings which are stuck in their
grooves, so every effort should be made to prevent rings from becoming stuck.
First, they should be installed with sufficient side clearance to enable them to
remain free while the engine is working under load at normal operating
temperatures. Second, every precaution should be taken at the time of assembly
to see that all parts of the engine are clean of any dirt particles which might
cause the rings to stick. Third, a good grade of oil should be used to lessen
the possibility of carbon or varnish. Fourth, the oil should be kept clean by
regularly scheduled oil changes and proper care of the oil filter. Fifth, every
precaution should be taken to keep the engine from becoming overheated from any
29. Late Valve Timing
Late valve timing will keep the intake valve closed too long after the
intake stroke has started, and will increase the vacuum in the cylinder. The
high vacuum will have a tendency to suck oil up past the piston and rings into
the upper part of the cylinder where it will be burned.
30. Oil Pressure Too High
An incorrect oil pressure setting or a faulty relief valve may cause the oil
pressure to be too high. The result will be that the engine will be flooded
with an abnormally large amount of oil in a manner similar to that which occurs
with worn bearings.
31. Oil Viscosity
The use of oil with a viscosity that is too light may result in high oil
consumption. Refer to the vehicle owner’s manual for the proper oil viscosity
to be used under specific driving conditions or ambient temperatures.
32. Piston Slap
Some late model engines meeting the latest emission requirements have
changed their piston design. This can sometimes lead to a light “knock” at
startup. In some cases this can increase oil consumption levels.
33. Internal Gasket/Intake Breach
Newer engine designs sometimes implement a combination of composite
materials and metals. Gaskets and seals can sometimes breach or become stressed
over time due to differences in heat expansion and contraction differences
causing oil consumption levels to increase.
34. Spark Knock
Most new automobiles have knock sensors to adjust timing to reduce emissions
as well as increase engine power and performance. Spark knock is due to
premature ignition of the fuel during the combustion process. Preignition
results in surges of pressure being forced upon the piston. This disrupts the
movement of the piston ring, resulting in a loss of ring seal on both the top
and the bottom of the ring, and ultimately allowing for increased blow by and
oil consumption past the rings. This may also occur due to a faulty mass air
flow sensor or throttle positioning switch.
35. Aftermarket Performance Chips and Modification
Increasing performance through the use of performance/power enhancement
products to a stock or factory engine can increase the chance of excessive oil
36. Lugging Engine
Lugging is running the engine at a lower RPM in a condition where a higher
RPM (more power/torque) should be implemented. This causes more stress loading
on the piston and can lead to increased engine oil consumption.
37. Inappropriate Operation of Overdrive
Operating the overdrive mode in conditions where it is not recommended will
cause the engine to consume oil for a variety of reasons. Such engines include
towing or stop-and-go driving in city traffic. See also reason #36.
38. Leaking Turbocharger Seal
A leaking turbocharger seal will draw oil into the combustion chamber where
it will burn and form carbon deposits which contribute to further oil
consumption as they interfere with proper engine function.
39. Restricted Air Intake
Excessive restriction in the air intake system will increase engine vacuum
and can increase oil consumption as noted in #24. A heavily plugged air filter
would be one example of this situation.
40. Fuel Dilution
If unburned fuel is allowed to enter the lubrication system, the oil will
become thinner and more volatile. Both will result in higher oil consumption.
Excess fuel can enter and mix with the oil via a leaking fuel injector, fuel
pump problem, and restricted air intake or through excessive idling.
Photo: Kent Whiteman is a
Nationwide Amsoil Platinum Dealer and is shown with his ITE SCCA
Road Racing Amsoil Sponsored Dodge Viper race car.
"New" - Register Now as an Amsoil Dealer
Registering now is just a click away
filling out a form and mailing to Amsoil for approval
immediately for just $15.00 for a 6 month membership
immediately for just $30.00 for a one year membership
Renewal is not mandatory
Become a Dealer full time or part time
Business provides long term secure income for Dealers and
Eligible to receive commission checks from Amsoil
It's fast and easy
is the undisputed leader in synthetics......
Since 1972, AMSOIL Synthetics have proven to be
the BEST. AMSOIL also engineers and
manufactures Super Duty Oil filters which have a 25,000 mile service life as
well as specialized filtration systems for commercial and fleet applications in
cars and light, medium and heavy trucks which can filter particles down to less
than one micron (a standard full flow oil filter can only filter to 20-25
microns with any degree of efficiency) making oil changes virtually
unnecessary and virtually eliminating engine wear. These filters have been
proven by millions of miles of over-the road trucks, construction equipment and
AMSOIL saves you time and money.
The only 25,000 mile/one- year and
35,000/one- year motor oil in the world.
Exceeds the most stringent performance
specifications of all major U.S. and foreign automotive and truck manufacturers.
Provides up to two-times the wear protection
of other motor oils.
Increases the life of your vehicle.
Improves performance, fuel economy and
Diesel oil and filtration products designed
to deliver 1,000,000 miles for over-the-road trucks before engine overhaul.
Used by many national racing teams, fleets,
police departments, construction firms and trucking companies.
Enhanced Synthetic Oil is comprised of a group of
highly skilled team of Engineers and Lubrication and Filtration Specialists.
You too, can join our group when you become an AMSOIL Dealer and take advantage
of all that we offer as you use products in your own vehicles or begin your own
AMSOIL business. You won't find a more knowledgeable and skilled group of
Dealers anywhere which is very important when you need support as you build your
In addition, as a Dealer in our group you will
receive exclusive unlimited product, technical and business support from the
only group of Truck and Automotive Engineers and Lubrication Specialists on the
We do not only run our business on the internet. We
also have numerous commercial, industrial, trucking, excavating, construction,
logging, police, racing and many more accounts that we support and service on a
regular basis. We have several fully stocked warehouses and fully equipped shop
facilities. This provides us with excellent knowledge of the products, equipment
and the business and the ability to respond
immediately to any of your needs. We
will use this knowledge and experience to help you get started so you too can
achieve your goals.
We possess the skills, desire and knowledge
to answer questions, solve problems, improve efficiency, reduce downtime,
maintenance costs and increase the durability and life of all of your vehicles.
Read what our
satisfied customers have to say about us. Read
through our website. Contact us with any questions. If you decide to become an
AMSOIL Dealer you will be joining, in our opinion, the most skilled AMSOIL group
there is. We will help you get started and provide you with the tools and
information in order to be successful in this business or with technical and
product assistance to use AMSOIL products in your own vehicles.
We offer several options to receive information on AMSOIL. We welcome the
opportunity to work with you personally as your servicing AMSOIL Dealer.
Please, email us at
we will send you an exclusive comprehensive package
of product, technical and business information.
If you are serious about AMSOIL products and the
business opportunity this is the best option. You will receive extensive
technical and business support from both myself and my AMSOIL Dealer Group. We
look forward to helping you learn about AMSOIL.
OR - for a
smaller, very general information package (which includes a catalog and Dealer
application) you can request information via any of the links below.
To request a FREE Factory Direct Catalog
For Information on Becoming an AMSOIL Dealer
To Buy AMSOIL Products in the AMSOIL On-Line Store
To Sell AMSOIL in Your Store or Purchase For Use in Your Businesses Equipment
To visit the AMSOIL Corporate Website for Product and Business Opportunity
is Proudly Made in the U.S.A.
Contact Us |
On-Line Store |
Enhanced Synthetic Oil, a Division of
Racers Products, LLC
Ogden, Utah 84403
Phone Toll Free:
Copyright© 2014 Enhanced Synthetic Oil
a Division of Racers Products, LLC all Rights Reserved. No part of this
authorized Amsoil Dealer website may be reproduced or distributed
in any form or by means, or stored in a database or retrieval system, without validated
prior written permission. Special undetectable methods are used that will identify any of this website material
copied, reworded, rewritten, and published to the web.
Like us on Facebook