Quote:
Originally Posted by malter2.0
My bad. I was under impression that 550 4.4 is also valvetronic. If that's the case the difference should be same as between N54 (no valvetronic) and N55 engine (valvetronic)...~2mpg diff.
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The N54 and N55 make similar power. The S63Tu and N63 do not. The increase in power by a significant amount - ~150hp - for the S63Tu could easily have offset any efficiency gains that the Valvetronic system provides. That the S63Tu is actually more efficient than the N63 in the EU cycle is actually pretty remarkable. However, as south mentioned, real world mileage may not reflect the same result. I am skeptical that the M5 will be the more efficient vehicle in practice.