Correlation between oil volume and OCI

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Hokiefyd

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I'm sure there's one to some degree, but is it linear? Say you have an engine that takes 5 quarts of oil, and has a manufacturer-specified OCI of 5,000 miles. I think most of us take it for granted that the engine will run just fine on 4 quarts of oil. In concept, should the OCI be reduced to 4,000 miles as well? In other words, if you reduce the oil volume by x%, should you also shorten the OCI by x%?

The same correlation would apply in the opposite direction. If you increased the oil volume by x% (either by a larger pan, huge filter, bypass system, etc), could you conceptually also increase the OCI by x%?

I know there are limited applications in practice here; this is more of a conceptual question.
 
I don't know how anyone can say for certainty without testing somehow, but I rather doubt the correlation is linear. If you reduced the oil level to 3 quarts you would probably severely reduce the OCI because those 3 quarts would get much hotter than the normal 5 quarts. Or maybe it wouldn't overheat if the car were driven only short trips, but then the acidity would get higher, requiring a sooner oil change.
 
I believe the first Versas with a 3 quart oil capacity had super short OCIs. Now that the same engine has a larger oil pan, it's been increased.
 
What's ford recommend with the DOHC coyote v8 in the newer 'stang vs. the previous 5.0 OHV engine? There may be a hint there. The OIl capacity was almost doubled, though engine specific output went way up.
 
Yes. Nissans for example are known for small oil sumps and their recommended OCI reflects that. My sr20 is about 3.8 quarts.
 
I don't know what the ratio would be, but it definitely isn't a linear relationship. A manufacturer of industrial equipment I deal with specifically uses sumps almost 2x the regular size to get longer oil drains. - they did a bunch of testing with different size sumps and filtration methods including bypass filtration units and got their service life up over 2000 hours.
 
My old ML320 had an 8.5 qt oil sump. I used to do 12-15K mile OCIs w/M1 and the maintenance minder still said I had some time left.
 
Last edited:
Originally Posted By: Hokiefyd
I'm sure there's one to some degree, but is it linear? Say you have an engine that takes 5 quarts of oil, and has a manufacturer-specified OCI of 5,000 miles. I think most of us take it for granted that the engine will run just fine on 4 quarts of oil. In concept, should the OCI be reduced to 4,000 miles as well? In other words, if you reduce the oil volume by x%, should you also shorten the OCI by x%?

Some musings of BITOGers on the effect of oil sump volume (as well as other parameters) on OCI...

https://docs.google.com/spreadsheet/ccc?...p=sharing#gid=0
 
Many European vehicles with large sump upward 7-8 quarts and even more than 10 quarts like Porsche 911 have long OCI up to 12-15k miles or longer.
 
Originally Posted By: Hokiefyd
I'm sure there's one to some degree, but is it linear? Say you have an engine that takes 5 quarts of oil, and has a manufacturer-specified OCI of 5,000 miles. I think most of us take it for granted that the engine will run just fine on 4 quarts of oil. In concept, should the OCI be reduced to 4,000 miles as well? In other words, if you reduce the oil volume by x%, should you also shorten the OCI by x%?

The same correlation would apply in the opposite direction. If you increased the oil volume by x% (either by a larger pan, huge filter, bypass system, etc), could you conceptually also increase the OCI by x%?

I know there are limited applications in practice here; this is more of a conceptual question.


My Cummins diesel has a 12 QT sump, and can easily go 18K mile OCIs. (Via UOA).
 
Short tripping a big sump will cause more problems than it solves. Other than that, if you drive 10 miles or more every time you start the engine, then a larger sump may give you a longer reasonable OCI.
 
Didn't VW have a 1.8 turbo engine with a small sump that was a sludger? They increased the sump size on that engine.

I would say that cutting corners with a small sump is not a good idea. Even my 30 year old Honda with a 1.5 engine and 76 horsepower takes 3.7 quarts.
 
My 03 530i had about the same sump of little under 7qts as my IS250. 5K on Lexus, and 17k on Bimmer....OLM on bimmer and set 5k reminder on lexus.My jeep is 6qt with 7.5k by the book. In real world, I believe there is a correlation, however from manufacturer to the next, they seem to follow their own logic.
 
A lot of the Nissan Sentras only hold about 2.6 - 2.8 quarts ... on a car like that I would probably be stuck to the 3,000 mile oil change just for my own peace of mind lol
 
Originally Posted By: OneEyeJack
Didn't VW have a 1.8 turbo engine with a small sump that was a sludger? They increased the sump size on that engine.



They did not increase the sump capacity per se, they specified use of a much larger oil filter and required use of synthetic oil meeting VW specs.

If the proper oil and larger filter are used = no sludge formation. I change the Passat's oil 2x per year regardless of distance travelled.
 
Originally Posted By: OneEyeJack
Didn't VW have a 1.8 turbo engine with a small sump that was a sludger? They increased the sump size on that engine.

I would say that cutting corners with a small sump is not a good idea. Even my 30 year old Honda with a 1.5 engine and 76 horsepower takes 3.7 quarts.


Yes, it was the B5 and B5.5 Passat. The engine was the same (mostly) as the one in the Jetta/Golf, but because it was longitudinal the sump was made smaller to fit over the subframe. Add to this they did not (early on) spec synthetic oil and the OCI was 5k miles. The sump/filter combo on this car allowed for (from 2004 on) 4.25 quarts; earlier cars with smaller filters were about 3.8 quarts.
 
My 2011 Tundra with the 5.7L has an 8qt sump but requires 5K OCI. However, in 2012 the OCI went to 10K.
 
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