Quote:
Originally Posted by Rockstock
I never thought about this until I tried to explain the results I was coming up with. I have a 01 Corolla which as most know tend to burn a little oil with higher mileage. I noticed that topping the oil off at fuel stops on highway driving trips cause a noticeable drop in MPG.
The oil never gets low enough for the check oil light to come on, but the level on the dipstick is about half way down. I fill to the full mark. My question is the minimum oil does the engine actually needs to achieve full lubrication. Read that question again before you reply with a biased opinion and no factual information. THIS IS A TECH THREAD NOT UNSUPPORTED OPINIONS.
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From the factory, the sump and oil level are designed to supply uninterrupted oil flow through the engine for extended periods at wide-open-throttle up to red-line or limiter imposed rev limit of the engine.
I have no idea what temperature range this is good down to.
I don't think anyone can give you an exact answer for two reasons.
First "to achieve full lubrication" - but under what conditions?
hypermiling? dirt-track racing?
Second, sump efficiency differs with design, and drain-back characteristics can be affected by many variables such as sludge build-up, core-shift in block or head, or the alignment of holes in the head gasket. Bearing leakage changes as clearances change, and that will obviously affect oiling requirements, pressure, and drain-back.
This is somewhat unrelated, but I know of a few drag racers who have got away with making WOT passes while 1.5 quarts low (3-quarts remaining) without experiencing pressure loss or problem. From this they saw a performance increase of between 10 and 15 HP based on their trap speeds at the end. I do know that they were using standard un-baffled pans, but one of them used a windage screen.
I do know that oil volume requirement is at least in part a function of engine speed, and thus low RPM cruising (hypermiling) would have less demand than what the system is designed to cover.