Quote:
Originally Posted by B192734
I've always been taught that the amount of oil that you should put in is what the dipstick says after sitting for a couple of minutes after driving till normal temp. That if youput more in that you are running the risk of a blown head gasket or worse. I've always been paranoid of anything to do with my oil. That's part of the issue...
So how full would you have to go before it starts to become a problem?
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Well there is no general rule as to how much over causes a problem. See every engine and pan design is different. There are a rew reasons that get kind of complicated but Ill try for the quick and dirty answer.
The first problem you have with overfull oil is a loss of power due to the crank running through to much oil. It is for this reason race engines use windage trays and crank scrapers to keep oil off of the crank at high RPM's.
In a street car or say a jeep 4.0 this would probably not be noticeable. If it became full enough that the crank was "whipping" the oil you would probably get a little foam and excess oil through the breather.
These symptoms would worsen the more overfull the engine was.
Untill you get it ful enough that the cylinders start to fill from the bottom up.
I have seen this first hand on a toyota 4cyl that was filled way overfull.
This causes loss of power and a go go gadget smokescreen. Again the severity depends on how far overfull it is.
The most severe is enough oil to cause a hydraulic lock. Liquids cannot be compressed. So when the cylinders become very full the piston cannot compress the oil and the engine will not turn.
This could theoretically bend rods and break rings but honestly the only time I ever saw this happen it merely fouled the plugs and causes said smokescreen after engine was drained ,properly filled and restarted.
Problems can occur in an oval track car when all the oil gets flung to one side of the pan and the engine starves. If this kind of thing interests you research some of the different ways the circle track guys have remedied this problem other than a dry sump. Ypu will see strange oil pans and baffles and oil levels all over the spectrum.