OK, but by how much and after how long? If we're talking 2mpg after 10k miles, that's a big deal, and worth doing something about. If we're talking .001mpg after 300k miles, then who cares?
I don’t disagree with that. There are many that have said no issues at xxx,xxx mileage. That’s awesome, no mechanical issues. Yet I’ve never heard talk about how the mileage still is same, Ect. Or how it’s had volumetric/fuel trim efficiency tests done after break in then at that end point? No just that it’s still running fine. CC is for maximizing combustion event/keeping combustion chamber clear of contaminated oil, which will help avoid mechanical failures as a side plus.
It’s a tool, just like people putting a additive in the tank every x fill ups/miles.
I get it and understand that the less money put into maintenance and still a great result of engine still works. I’m not bashing that. That doesn’t mean there wasn’t degrading of efficiency & fuel mileage. It’s a slow process, the fast pace world we live in it’s easily over looked.
Honest true answer would be 30-50k is starting to degrade and become less efficient. Definitely 50k at the same, still so many variables to add or subtract miles from that.