'Normal' oil consumption

[hansforum]

If we compare two equal engines that use the same type of oil, is it possible that they use different amount of oil and still have the same fuel consumption and power generation? In other words, is engine that use less oil better engine?
Car manufacturers say that up to 1l per 600-1000 miles are still normal consumption.It is possible that one new car uses 0.1l in 7500 miles and another new (same brand, same model) uses 1.5l in 7500 miles. Is it possible that these engines have the same power figures?

 

[MiketheEngineer]

My F150 uses about NO oil in 4,000 miles!!

Some engines however will do that and it can easily vary from engine to engine. Kind of depends who was tightening bolts, setting rings and gaskets that day!!!

 

[dgallup]

Yes.

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[MikeHalloran]

It's not just possible that engines with different oil consumption have the same power, it's likely, provided they have the same chip revision.

One thing I've noticed: 40+ years ago, 1.0 l of oil lost per 600-1000 miles was also called 'normal', and was in fact representative of most of the new engine production at the time.

Now, <l.0 l in 7500 miles seems to be more typical.

I'd guess it's because of better seals, better rings, automated assembly, EGR, and semi-closed crankcases.



Mike Halloran
Pembroke Pines, FL, USA

 

[Tmoose]

If the engines are of 70s vintage air cooled 2 stroke design, intentionally using more oil can result in more horse powder.

http://www.bridgestonemotorcycle.com/documents/oilpremix6.pdf

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If a 4 stroke engine is allowing much oil at all into the combustion chamber the effective octane is reduced, which >could< require pulling back the ignition timing to reduce detonation, and >could< result in less power, too.

I'm not sure I'd expect a strict connection between oil consumption as a measure of 4 stroke engine assembly quality, internal condition or power output. for instance, a crankcase ventilation system overdue for maintenance could drive the oil consumption up, even though mechanically the engine could be in fine shape.

 

[evelrod]

hansforum---It is possible (within reason, of course) for two seemingly identical engines to have somewhat different oil consumption rates and still have approximately the same power profile. Approx because no two engines are ever identical if you look at them closely enough.

Mike---Yeah, my '49 Mercury was only 8 years old and used about a qt. a week and the dealer said that it was "normal"...
Today most Ford products have such marvels as "sealed automatic transmissions" and it is not at all uncommon for a new engine to have 'zero'(?) oil consumption at extended service intervals. I chalk it up to better mfgr techniques, metallurgy, lubrication...that and the 'march of time'...seems like yesterday, doesn't it? My old Dodge/Cummins has over 300k miles and it still does not "use oil"...less than a half qt. in 3000 miles!

Rod

 

[patprimmer]

Short answer. Yes

Slightly longer answer. RIR (Rod Is Right)

Bore finish, ring end gap or side clearance, pistom oil drain back holes and valve stem seals can all have a large impact on oil consumption from burning without necessarily having any real adverse impact on power.

Of course oil leaks have no influence on power whatsoever but it makes an obvious mess.

Manner of use also has a strong influence on oil consumption.

Regards
Pat
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[Lou Scannon]

Though it's probably a very minor effect in most cases, the oil level may be getting continuously "topped up" via absorption of moisture & hydrocarbons from blowby, and gasoline that may be wetting the cylinder walls when the engine is cold.

 

[evelrod]

hemi, here in SoCal, all things considered and, while I agree that scenario is possible, it's a bit of a stretch in the majority case.

However, somewhat in favor of your hypothesis, I did have one fella working for me that claims he drove a new Ford Bronco V8 100k miles without changing or adding oil......Okay, I hear ya. But...this fella was from Jamaica and, not meaning any disrespect to most Jamaicans.....One day I gave him my new gloves, his had big holes in them. Thanking me with big smile...made me feel good. Next morning he had put duct tape on all the fingers...said it made them last longer. I dunno! Maybe he actually did drive a Ford V8 that long without adding or changing oil.

Rod

 

[patprimmer]

Blow by on a cold engine does add water to the sump and can raise the oil level or offset the losses on an engine that is used in a manner that never gets the oil very hot such as mommas grocery getter.

If that happens and the oil is not changed before the next occasion the car sees a reasonable distance on a highway, all the water boils off and the level drops noticeably in a very short time and leads people to incorrectly conclude their engine only uses oil at high speed.

Regards
Pat
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[hansforum]

I know that new engines have power generation tolerances. It could be for example 5% up and down from declared power. So I thought that these that are down in power because engine parts tolerances could consume more oil than more powerful ones. If bore finish, ring end gap or side clearance are not optimal because production tolerances engine will have few hp down because it's compression will be slightly lower, so I thought that through that clearance more oil will end in combustion chamber and more of it will burn.

But you say it's not necessary the case, can you give more information about it. Is it possible that oil consumption increase rapidly with even slight wear and very small power loss due to wear?

 

[thundair]

I use oil in my 10 year old Z06 and I was told it was from ring flutter when running at high RPM without load.
I guess it would be the long sweeping corners where your not really pulling but feathering the throttle.

I don't know anything but the people that do.

 

[dicer]

Oil consumption is not the yardstick to determine if its a better engine or not. It can reflect on the parts used and or the person or persons that put it together, machined it etc.

 

[patprimmer]

A coarse bore finish can hold more oil on its surface below the plateau that the rings ride on. This can increase oil consumption while having no impact on blow by.

Poor valve stem seals have no impact on blow by.

Wider piston to bore might allow a little more blow by but might also reduce friction.

Etc etc etc. It really is much more complex than you seem to realise.

Regards
Pat
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[izzmus]

Apparently, late model Accords are having oil consumption problems.

Problem, in this case, being that even when new they use one or two quarts of oil between oil changes, and the people who bought Accords want a hands-off transport appliance without any of that bothersome looking-after. (My guess is that Honda went a little too light-tension on their piston rings, in order to squeeze out that last drop of fuel economy)

At the opposite end of the spectrum are rotaries, which can and will go overfull with use, if the oil injector unit is disabled. My personal car adds roughly one quart per 600mi.