Just did a trip from Tampa Fl. to Indianapolis In. and back. Did 80mph whole time, 3400 rpm.
30mpg with a/c off and 28 with a/c on. 1993 190 2.6 auto 84k miles.
Have a 1.8l VW Jetta. 70 mph 3200rpm 200k miles doesn't burn a drop of oil.
If an engine is designed to run at high rpm it will be fine.
Just my .02 cents