Oil Temp

[ClipperLuna]

A V35 POH I found online cautions not to run the engine past 1200 rpm until the oil temp reaches 24C. Is this precaution just if you're running straight-grade, or is it for any oil?

[Jacques]

I think the precaution “should” stand for both single and multi grade oils. But it is an interesting question you pose and I’m not qualified at all to say with certainty the correct reasoning. But, I think that warming the mechanical parts of an engine to a certain standard as measured by a set oil temperature, probably goes a long ways in preserving the life of your engine.
I don’t have the Bonanza yet, so I can’t really test it with you, but it would be interesting to run through a few scenarios to see if you encounter damage more consistently by running up the engine past the recommended power settings at those lower oil temperatures!


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[cristi.neagu]

I imagine the straight grade oil should have no issues at any temperature, since it should have the same viscosity across a wide range of temperatures. The problem should be with multi grade oil, since it is more viscous at low temperatures, therefore it cannot flow and lubricate properly.
But the biggest issue is with heat expansion. Engine parts are designed to work properly at normal engine working temperatures. At lower temperatures, parts may have tight fits which leads to premature wear.

[AKar]

A V35 POH I found online cautions not to run the engine past 1200 rpm until the oil temp reaches 24C. Is this precaution just if you're running straight-grade, or is it for any oil?

Continental's instructions for oil temperatures do not discern the oil grade used, so it applies in any case. Generally, Continental is more careful in their oil temperature recommendations than Lycoming is. Technically, the engines should be all but the same.

I imagine the straight grade oil should have no issues at any temperature, since it should have the same viscosity across a wide range of temperatures. The problem should be with multi grade oil, since it is more viscous at low temperatures, therefore it cannot flow and lubricate properly.

Exactly the opposite. Multi-grade rating is not to imply that the oil would be particularly thick at cold, but that it is graded both hot and cold. Multi-grade oils are used for the very purpose to allow for reduced viscosity when cold while avoiding the necessity of using too thin oil when hot. Every oil gets thicker when colder, single-grade ones included. Multi-grade oils are essentially oils as thin as their W-rating but with added components that behave the opposite to the usual, increasing the viscosity of the oil as it warms up, offsetting some of its... thinning behavior.

Single-grade oils have their viscosity specified at only one temperature, and generally perform worse over wide range of temperatures. Albeit our 20W is hardly too thin stuff when cold either...

-Esa

[ClipperLuna]

Thank you all. That makes sense if the reason is about parts tolerances rather than issues with the oil itself. My original thought was it might be because, if you're running straight grade, problems might crop up from the oil system having to push stuff that's too thick through it. I've heard that on the Ford Essex engine, under the right circumstances (including running oil of too high a viscosity on too cold of a day and the pressure regulator sticking), the oil filter's gasket will blow-out.

That would be interesting, Jacques, to test it and see what happens. I'll give it a try, though with how often I fly it might take awhile before we see any effects.