quote:
Please settle a difference of opinion.
All things being equal, which is harder on my engine:
traveling 500 miles at 50 mph, or going 500 miles at 75 mph?
My other half justifies her 75-mph theory with the shorter time the engine is working.

Which uses less fuel? And if you could cite research sources, that would be appreciated.

http://www.bridgestonetrucktir...cial4_fuel-speed.asp

http://tinyurl.com/kbn2s8x

http://goo.gl/r5P5Ur


:unquote

I'll cite your own source:
"Increased engine wear

And tires aren't the only thing that suffers. Engine manufacturers estimate maintenance costs may be as much as 10-15 percent higher at 75 mph than at 55 mph. Engine durability could also drop 10-15 percent."

Isn't it obvious?

Rule-of-Thumb: Most vehicles' most efficient speed is ~45 mph