The DOE rates the '99 E150 with 4.2l V6 at 13/17 mpg and the 4.6l V8 at 12/17 mpg. Since mpg is basically a wash, which engine is more robust and/or reliable? Is the bump in HP and torque worth dealing with an OHC engine? What's the service life of the chain, guides, tensioner, etc.?

Thanks,
Sixto
87 300D^2