How does oil Level effect FE
 

My van was a little over the safe mark on the dipstick, so I drained some so it would be half way between min and max. I read somewhere that it's better to be under full for better FE. Can anyone comment. Thanks.

Some engines are designed so that the crankshaft is actually partially submerged in oil. When the engine is running the crank must then turn through this oil. This is called "windage". When your oil level is low there is less oil for the crank to strike.

I currently run my car on the low side. Its what I consider a freebee mod. This is dangerous if your uses large amounts of oil. I check it often.\

BTW pop, your numbers are looking very good. You have a big comfortable van there getting mid 20s, very respectable.

I don't know what the "official" answer is. But in my limited experience with our cars, FE seems to take a dive when the oil level is down for any reason (even it it's still above the "low" mark. That's why I try to be as close as possible to the "full" mark as I can get.

BTW: Having the car "full" (but not over full) should also be better on the engine, as it give you a little more oil to carry away heat and engine grime with. i.e. a bigger oil sump is (all else being equal) "a good thing" for an engine.

over filling the crank case will drop your mileage if your car is not made to do this.

You also want to take burning oil into consideration if you have an old car. I burn .5 quarts every 3ooo miles, so if I purposly put it low, it would be dangerously low by the time I changed oil.

popimp -

I don't know if this helps. I got this image out of a Saturn manual on CD :

Attachment 938

It's not about FE, but how to interpret your oil level hot or cold.

CarloSW2

oil 1/2 qt low on my racecar added 20 hp at rear wheels, so figure about 5% penalty if oil level is too high

Carlos:

My owners manual says this

The best time to check the engine oil level is about 5
minutes after a fully warmed engine is shut off or before
starting the engine after it has sat overnight.
Checking the oil while the vehicle is on level ground will
improve the accuracy of the oil level readings. Maintain
the oil level between the MIN and MAX markings on the
dipstick. Adding one quart of oil when the reading is at
the MIN mark will result in a MAX reading on these
engines.

CAUTION!
Overfilling or underfilling will cause oil aeration or
loss of oil pressure. This could damage your engine.

The sunfire we had burned a good bit of oil 2-3 quarts every 3-4k. It was run on many occasions with 2 quarts + low. No this is not good for your engine, but it didn't seem to mind. I rarely checked the oil in the sunfire. I hated that car for no other reason than it was domestic and it returned ill for good. You could always tell when it needed oil, the oil light would flicker on a hard turn. LOL. So my conclusion is running 1 quart low is harmless but not generally recommended.

On my wife's Saturns the timing chain noise was always a tell-tale sign... woops! LOL