Why should the oil level never be above the fill line

I am no engineer, but as I understand it if the oil is over-full, when the camshaft spins within the engine it contacts the top of the oil and whips it into a froth. Froth, as it turns out, is quite poor at lubricating all these rapidly moving metal pieces. As a result engine damage occurs

The oil-over-full bad-thing rule made absolutely no sense to me before I heard this explanation, but now it makes some sense.

Perhaps someone on this board who *really* knows will enlighten the both of us

Peace :mrgreen:

 

Actually too much oil in the crankcase could overload some of the mechanical parts due to hydraulic resitance. Also it could case oil to be ingested into the intake manifold through the PCV valve.(lots of smoke and carbon deposits would result.) This is true of almost any modern reciprocating piston ICE ukeright:

 

Actually, Jeffrey is correct, except I'm sure that he meant "crankshaft" and not "camshaft." If the crankshaft (and especially the connecting rods) are in contact with the oil, it can froth up the oil, which may result in lubrication problems. You don't need to be concerned if the level is an 1/8" or so above the full line, but any more than that would be too much. Also, keep in mind that the car needs to be on a level surface when checking the dipstick. In some cars, even a slight grade will give erroneous measurements.

 

Older, high performance V-8's used to be fitted with "windage trays" mounted just beneath the crankshaft's lower reach. This would separate the crank from sloshing oil in the pan, while allowing pass through via numerous slots. A high reving crank (particularly a massive, deep axis one) does not appreciate slapping into anything. The result can be increase bearing wear, but more commonly, oil froth which is bad for the lubrication system.