Filling oil just to min line? better mpg?

[Frank Lee]

Originally Posted by suspectnumber961

Lapointe recommended over filling by a quart or so...he was into gaining mpg for sure.

Bwwahahaha good one.

[Trip]

As long as you are in the crosshatches on the dipstick, you are safe.

The crankcase oil has two main jobs - lubricate and remove heat. In hot weather and stop and go traffic, full to the top is better to help dissipate heat. Racers use deep sumps and finned pans for this purpose.

[Frank Lee]

Removal of excess heat isn't very often a problem for folks like us.

[Rainh2o]

Racers also use deep sumps because when they corner or take off fast the oil will shift or flow back or to the side, and if you have low oil in your pan, or a shallow pan, your oil pump will go dry for a few secs, which is not good. If oyu have lots of step hills or sharp corners, like in some parts of Arkansas, you will want it full to the max for this purpose.

[Frank Lee]

Next time I'm in Arkansas I'll keep that in mind

[Rainh2o]

Some of those back roads in Arkansas are murder for turning and hills. That was the first place that came to mind for that example. Your often going down a hill and around a 130 degree turn on a very narrow 2 lane road that has no shoulder...

[Christ]

And should be going at a slow speed for such turns, safety kept in mind.

Most racers use gated pans... the depth of the pan is for extra capacity, but not to keep the engine from oil starvation.

[thatguitarguy]

I don't believe there's any advantage to being outside the levels marked on the dipstick. I do think it's bad to have too much oil in your engine, as well as too little. If racers have more oil, it's because they have larger pans, not because they overfilled the crankcase.

The oil pump draws from the lowest point in the pan. If your oil level is even with the lowest line on your dipstick when measured on level ground, Your engine should not be starved of oil unless you've layed your car on it's side or flipped over already, and at that point, concern about oil starvation should be a lot lower on your list of worries.

When I was younger and stupider, one time I hit something in the road that punched a hole in my low hanging oil filter. I had an oil pressure gauge, and I saw it go to zero, but I kept driving till I got home. I replaced the damaged filter, filled up the oil, and never noticed any ill effects from the episode. I never opened up that engine to see if there was scarring, but I drove that car for many tens of thousands of miles after that, and never had a problem.

Another time in another car, I had the oil light start flickering on for no apparent reason, and I stopped and checked the oil, but the level showed full. I put more oil in anyway to try to get to a place where I could check it out under better conditions, and that trip ended with holes being blown out both sides of that engine. I did open that one up out of curiosity, and all the pistons were whole, but one was seized. I've since wondered if I blew that engine by putting too much oil in to the point where the pistons couldn't freely move downward because there was oil where there should have been air. Air compresses. Oil does not. I don't know the answer.

If you purposely overfill your crankcase, I don't expect my misadventures to change your mind, and if you figure that because I ran my engine with no oil in it, then you might be able to get away with it too, then you must be as young and stupid as I was a long time ago.

Anyway, I figure that the people that designed the engine have much better reasons for recommending certain oil levels, than I have for going outside those recommended levels.

But that's just me...

[Christ]

Too much oil doesn't prevent the cylinders from moving at all... it just makes it alot harder. While oil doesn't compress, it does move. As one piston is coming down, another is going up, so the fluid is getting forced elsewhere in the crank case. The last thing that would happen from that is a seized piston. More likely what happened was that the flickering oil light was from a failing pump, and intermittent pressure, but without seeing the engine first hand, my guess is as good as the stuff in the cat box.

[Thymeclock]

Originally Posted by Trip

As long as you are in the crosshatches on the dipstick, you are safe.

The crankcase oil has two main jobs - lubricate and remove heat. In hot weather and stop and go traffic, full to the top is better to help dissipate heat. Racers use deep sumps and finned pans for this purpose.

Actually there is another important function, which is to keep impurities in suspension in the fluid. When you change your oil, it removes the harmful crud that is suspended in the dirty oil.

I've heard the comparison made between a vehicle and the human body: your car doesn't really run on fuel - it runs on oil. The gasoline is comparable to the food in your stomach, but the vehicle's oil is comparable to the blood in your circulatory system. I guess we could stretch it to say that an oil filter is something like the liver that removes most of the impurities and an oil change is somewhat like getting a blood transfusion.