VW - Case Paint

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What kind of paint should I use on the crankcase?

Over the years I’ve used a variety of different oil-based paints. With the exception of flat black primer, most stood up fairly well. Oil-based paint is usually okay up to about 400 degrees Fahrenheit and since the crankcase is never hotter than your maximum oil temp, that gives you a wide margin of safety.

My favorite is Rustoleum Flat Black. You want the flat-black because it has a better heat-tranfer index than glossy. If all you can find is Gloss Black, simply cut it about 1:4 with unleaded gasoline(!) or naptha. That causes the paint to dry dull instead of glossy.

Avoid ‘high temperature’ paint at all costs. Such paints get their high-temp properties from clay or metallic salts, both of which make excellent insulators.