Mercedes' (and RBR's?) "compression ratio trick" could be worth 4 tenths in Monza, and even more in the opening laps (~21s over a race: the difference between P2 and P6 this year)!

Let’s look at the numbers!

16:1 → mandated ’26 compression ratio (cold engine check)
18:1 → ’25 level (~ upper knock limit)

Reaching 18:1 in ’26 via thermal expansion would yield ~10 kW (~13 hp), requiring only a ~0.5 mm geometric change.

Currently, +13hp ICE power is worth ~0.26s/lap in Monza. But '26 ICEs will be far less powerful (~540hp vs ~840hp), so the same gain matters much more, since the ICE feeds the battery!