[500_19B]

I thought I read somewhere that the Mahle CR is calculated based on zero deck height... is that correct?

FWIW, I put Euros 3.2 P's and C's on my new rebuild. We have 94 octane freely available in Toronto (Petro Canada), but it has Ethanol. The choice I prefer is the Shell V-Power, which in Ontario is Ethanol-free but 91/92 octane. For my motor's start up, I used the Shell fuel.

I discussed this with a reputable local builder (who also did all the machine work for my rebuild) and he suggested I use 0.5 mm thick cylinder base gasket. He had done that many times in the past and had no trouble with Euros on our 91/92 gas and consdered the thicker base gaskets a bit of "safety margin".

When I calculated the theoretical difference in CR from the extra 0.25 mm of base gasket, it lowers from the specfied 10.3 to 10.0, which is half-way back to U.S. spec CR. Of course, the true CR is almost certainly much less - it just amazed me how much of a difference a quarter millimeter made...

The motor displays no signs of detonation on the Shell fuel.

I have heard that California is a tough place for quality fuel.