I get about 32-35 Combined city n highway. On te highway I go about 60mph, 2,500 rpmn I get about 42 mpg, but if I go about 75-80 mph the rpm goes up to 3,000 n engine gets a little loud, is that something I should worry about ???
Does it hurt my engine???
I'm trying to just to keep the rpm about 2500 n no more.

__________________
1999 W210 E300 Turbodiesel