2X -- but the incremental lifespan of a detonating engine with forged pistons (v HE cast) is not a whole lot longer.
Stock replacement pistons put you in the 10-2-10.5 range depending on the cyl heads, you need to build for the fuel you have in the area. IIRC, euro pump gas premium is something like 96 octane, so a cast rebuilder piston should be okay.
Only problem: with the cost of gas, a fill up is more than the pistons!
BOB
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