What would be the difference between a cold and hot compression. Would a cold test come up higher due to shrinkage?
Would new compression be lower for a non-turbo 300 due to a lesser compression ratio (21.5:1 vs 21:1)?
Am buying a non turbo 300D. Cold test was 1=255, 2&3=260, 4&5=270. The body and interior are excellent, etc. Has 194k.

Pistons and rings expand when heated.... so the fit in the bore should be tighter when the engine is at working temperature. Pistons expand different amounts in different directions due to the influence of the structure through which the piston pin goes. Some are manufactured in Oval shape to compensate for this. I would expect compression to be less for the non turbo engine. You mention 'new' .... compression should get better up to a point after new... if proper 'breaking in' happens... then there should be very little change for hundreds of thousands of miles on a properly lubed diesel engine.

Thanks. I forgot about mass with the expansion.

Jeff