Quantifying leaks vs. burning via color and UOA

[bulwnkl]

I like your idea. I wonder whether, in the case of consumption rather than leakage, the source of the oil affects the degree of darkening and increased combustion smell.

For example, suppose the case of poor ring-cylinder seal. It seems to me that should increase the contaminants and smell rather quickly like you suggest.

For a second example, suppose leaky valve seals but good ring-cylinder sealing. In that case oil is being burned (I suppose it's actually being leaked, isn't it?), but it seems that it shouldn't particularly increase the contaminant levels in the sump. It will mainly just be burned and pushed out the exhaust, or burned on the exhaust vlave itself if it's an exhaust valve seal leak.

What I do know is that my Subaru is easy. I can see the oil leaking past the cam tower seals (not sealed from the factory with a regular gasket, but rather with a sealant somewhat akin to Permatex) and the head gasket down onto the exhaust manifolds. I only notice the smell of smoke when I stop.

 

[MN Driver]

Sorry, might be a little off-topic, but doesn't it take a little more than 3000mi/qt of oil burning before you can see it in the exhaust?

 

[JHZR2]

no idea, thats why Im posting to begin with...

JMH

 

[kreigle]

quote:

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Originally posted by MN Driver:
Sorry, might be a little off-topic, but doesn't it take a little more than 3000mi/qt of oil burning before you can see it in the exhaust?

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My car burns 1qt in under 500 miles and I see no smoke. The converter burns it off. I think that regardless of how much oil the engine is burning you would only see significant smoke if the cat was loaded up with soot or not functioning.

 

[JHZR2]

I have to wonder how much oil those hondas that young kids drive burn. The ones that you know have been driven very hard... I see a puff of smoke at every stoplight, every shift, etc.

JMH

 

[Palut]

quote:

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Originally posted by JHZR2:
I have to wonder how much oil those hondas that young kids drive burn. The ones that you know have been driven very hard... I see a puff of smoke at every stoplight, every shift, etc.

JMH

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It doesn't help that those guys like to drive through parking lots at high rpms. In showing off, they're actually trashing their bone cold engines.

I can't tell you how many people I see starting their cars after class, and driving around at 4k+ rpm, just to hear their farty riceboy exhaust notes!

 

[LarryL]

You do have a problem finding oil that is going away. Oil can blow by the rings and valves and you will never see it and you may not smell it until it really gets going. It is possible to loose something like a quart in a thousand miles and not see it, and smell is dificult around a lot of other cars. We had a mystry car int he shop that ate a quart+ every 500 miles. Everyone took a shot at it but no one answer stuck. It was a Honda and we replaced the valve seals and a solenoid that holds the throttle open on overun and the problem was gone just like that. Oil consumption went to about 1 to 2 quarts every 5k miles...normal. That oil was not leaving through a leak.

 

[oilyriser]

Spark plugs tell the story -- ash, from calcium, or oily carbon buildup, from burning oil.

 

[JHZR2]

Hi,

I would appreciate opinions and information pertaining to my idea.

I propose that one can tell the cause of oil loss (leaking vs burning) via analysis of their oil and/or study of color. Why? If one has a leak, there ought not be any sort of difference to any of the normal specifications or tests that are done to regular motor oil.

If one is burning oil, I believe that (a) the oil will darken faster due to combustion byproducts, since oil will certainly not combust as easy as naphtha, gasoline or even diesel in a spark ignition engine (b) insolubles would be higher due to higher soot loading from improper burn (c) the oil will smell stronger like combustion, i.e. have more of a burned/exhaust smell to it (d) oxidation/nitration will increase due to likely more combustion gas and byproducts being mixed into the oil: if the engine cant keep the oil controlled, how can it keep the combustion gases during work?

Is this the case?

All I know is that my BMW emits no smoke under any circumstances, not downshifting, not between shifts, not at startup, not after idling, NEVER. However, I loose about 1 qt/3000 miles. climbing underneath doesnt help me to figure where the oil is going - I see no leaks. My oil (rotella syn 5w-40) stays a nice medium amber through 3000 (thats how many miles are on it right now), overall looks clean.

So my guess is that if I had a burning issue, the oil would look darker and nastier, and that UOAQ would be worse as well.

What do you experts think? If you burn oil and dont make it up with extra, does it effect your bulk oil, or does it just escape with the rest of the combustion products?

Thanks!

JMH