Oil consumption question (generic)

[MajorCavalry]

How did auto manufacturers come up with the "industry standard" that 1 quart per 1000 miles oil consumption is acceptable? Seems arbitrary and simply a way to avoid correction of poorly manufactured engines.

The only thing I can think of is that if the engine was manufactured with all of the tolerances at the extremes it could use this amount of oil. Example, piston bore at the oversize extreme and the piston at the undersize extreme, etc.

Any insight?

Steve

 

[Burt]

Good question. I assumed it was that spark plugs would foul if consumption was higher. But I don't know.

 

[TallPaul]

Maybe what they could get away with on avoiding warranty rebuilds?

 

[MajorCavalry]

Originally Posted By: TallPaul
Maybe what they could get away with on avoiding warranty rebuilds?


This is what I am thinking, but why has no one questioned the validity this?

 

[MajorCavalry]

Maybe a representative of an auto manufacturer could chime in with the supporting documentation as to why this 1 QT per 1000 miles is NOT an arbitrary number. Ya right...

 

[Charlie1935]

In 1969 I had a Chrysler factory rep tell me that a quart in 900 miles was normal for the high performance 383.
In the day of the 1000 mile oil changes if we only used one quart between changes we thought that was good.

 

[Artem]

It's mass produced engines, made by the lowest bidder, what do you expect? Not every engine coming off the assembly line will be perfectly made and perfectly put together hence why burning a quart in 1,000 miles may be acceptable because even though there's technically nothing wrong with the engine, its not really perfect either.

That's my view on it.

This is not getting into the topic of certain engine designs which are made to burn some oil for better friction reduction and higher engine speeds (Take Honda's K series engine for example)

 

[supton]

I'd think these days that it'd lead to catalytic damage. Then again, perhaps that is factored into the design: if the engine burns a quart of oil per 1kmiles, then the catalytic must keep emissions "legal" until 120kmiles(?) is exceeded (or whatever the emissions warrenty is).

 

[TFB1]

Originally Posted By: Artem
It's mass produced engines, made by the lowest bidder, what do you expect?

Since when???

AFAIK all auto mfgr's build their own engines, or on a few cases buy from another mfgr(Cummins for Dodge diesel, Yamaha for the older Taurus SHO etc), no low bidder in the picture...

 

[RamFan]

I'd be curious as well. My 3.5l consumes but from what I've gathered as long as compression is still within spec then I shouldn't have any problems, especially since the 3.5l is known for consuming oil. Now I just need to get myself out to the store and buy a compression test kit and get to learning how to do it.

 

[MajorCavalry]

All these statements are more rationalizations rather than validations. No offense to anyone.

 

[Hokiefyd]

An acquaintance of mine is a GM powertrain engineer. He told me before that the seemingly wide range of "normal" oil consumption is mostly explainable by the tooling used to bore and hone the cylinders. The honing stones obviously wear with use and get changed at specific intervals. He said they also tend to "smooth out" with use. So the very first engine machined with new honing stones may have a very aggressive hatching pattern that would tend to correlate with a higher rate of oil consumption due to the tendency for oil to be retained on the cylinder walls with the deep hatch marks. Then maybe the last engine produced on that set of tooling will have relatively smooth cylinder bores that don't retain as much oil and that won't consume as much as the first engine might. This is why one engine may use two or three quarts of oil across an OCI and an otherwise "identical" engine may use nothing.

Another factor in greater consumption rates today compared with older engines is increased engine speed. Things like valve stem guides are lubricated with oil from the cylinder head, and once it's in the guide, it'll get sucked into the cylinder and get consumed. When you imagine that a certain volume of oil is "consumed" with each up-and-down motion of a valve stem, it makes sense that an engine with an average speed of maybe 3,000 rpm would consume more oil than an engine that sees an average speed of maybe 2,000 rpm.

 

[SteveSRT8]

Originally Posted By: MajorCavalry
How did auto manufacturers come up with the "industry standard" that 1 quart per 1000 miles oil consumption is acceptable? Seems arbitrary and simply a way to avoid correction of poorly manufactured engines.

The only thing I can think of is that if the engine was manufactured with all of the tolerances at the extremes it could use this amount of oil. Example, piston bore at the oversize extreme and the piston at the undersize extreme, etc.

Any insight?

Steve


Actually, back in the 60's Chevrolet even allowed up to one quart in 500 miles for its big block motors!

The simple facts are that while precision is up the bean counters control everything, meaning if they can save a nickel they will try! Engine complexity is on the rise and there will always be some variation from motor to motor.

 

[supton]

Originally Posted By: MajorCavalry
All these statements are more rationalizations rather than validations. No offense to anyone.


But why is oil consumption bad? If the catalyst was designed to handle 1qt/1kmile consumption, and last 150k+miles w/o increase in pollution--why would it matter?

Might as well argue that fan belts should last the lifetime of the car. Or wheel bearings, or tie rods, or __.

 

[MajorCavalry]

Originally Posted By: supton
Originally Posted By: MajorCavalry
All these statements are more rationalizations rather than validations. No offense to anyone.


But why is oil consumption bad? If the catalyst was designed to handle 1qt/1kmile consumption, and last 150k+miles w/o increase in pollution--why would it matter?

Might as well argue that fan belts should last the lifetime of the car. Or wheel bearings, or tie rods, or __.


I never stated that oil consumption, per se, is bad. I just wanted to know where the magic number of 1 qt / 1K miles came from. I would expect MUCH less variability among samples. How one engine can use no oil in a 7.5K mile oil change and another use 1 qt/1k miles (same engine family) and both be normal makes little sense to me. I would have expected to see a range of, perhaps, 1 QT per 5-7K miles as a normal variation.

Certainly increases cost of ownership. I use synthetic oil, Redline, at approx $10/qt my 20K per year mileage would cost an extra $200. Adds up[ over the years

 

[R2d2]

Seems like Hokiefyd had a plausible answer.

 

[supton]

In your OP, you stated "simply a way to avoid correction of poorly manufactured engines", thus implying that you do indeed think such oil usage is bad.

[I do have to admit to trading out of my Saturn when it hit 3k/qt. But then again, I really wanted my TDi, so perahps it was a convient scapegoat.]

As for cost: $200 per year, over 10 years is $2k. Good sized chunk of change, I'll give you that. But how much was depreciation/tires/brakes/etc over that time?

I'm not going to disagree; 1k/qt does seem really bad to me. Of course oil usage won't get better over time. I guess I'd be curious if a 50kmile vehicle that burns at that rate will still go another 100k at that rate; or if oil usage would skyrocket.

 

[Hokiefyd]

Originally Posted By: supton
Of course oil usage won't get better over time. I guess I'd be curious if a 50kmile vehicle that burns at that rate will still go another 100k at that rate; or if oil usage would skyrocket.


As long as the oil consumption isn't due to a failed component, it should not increase over time. When I say "failed", I'm talking like valve guide seals in an older Mitsubishi or Ford Modular, or stuck piston rings in an older Cadillac Northstar or Saturn 1.9L.

In fact, when oil consumption is due to an aggressively-hatched cylinder wall, you'll probably find that that particular engine will live a longer-than-average life due to the generous lubrication in the cylinder bore. Ridge reaming used to be a common thing 50 years ago, but with today's "looser" piston rings and aggressive cylinder hatching, that kind of wear is almost a relic of the past.

 

[TallPaul]

Originally Posted By: supton
But why is oil consumption bad?


If it does not mess up the converter, I would guess it could lower the octane of the mix and cause pinging or electronic engine adjustment to avoid pinging that may not contribute to the best performance/fuel mileage?

I know my '92 Aerostar 3.0 uses a quart every 1300 miles and 1) it's exhaust stinks which may mean a ruined cat, and 2) it has has an incurable pinging problem that has requried higher fuel grade. Once tried retarded timing and the thing could hardly get out of it's own tracks.

 

[D189379]

Originally Posted By: supton
I'd think these days that it'd lead to catalytic damage. Then again, perhaps that is factored into the design: if the engine burns a quart of oil per 1kmiles, then the catalytic must keep emissions "legal" until 120kmiles(?) is exceeded (or whatever the emissions warrenty is).


This is what I think. 1 liter every 1000 kms probably keeps sensors and the cats from dying before the warranties are up. I guarantee it's nothing more than a cost per warranty claim formula.