MrTcana and Lightman have both added valuable comments to this discussion.
However, I can not agree on the reported fact that diesel engines are much harder on oil than a gasoline engine. If you re-read my previous comments, I did not say that diesel engine are not being as hard on oil as gas engine. I said:''Not significantly harder on oil than a gas engine''. I can't argue on the fact that compression ratio on a diesel engine is much higher than in a gas engine and that pressures are much higher. It is a fact. But, diesel engine have much larger crankshaft/bearing journal and piston surface skirt area to spread the load. This result in a similar pressure/sq area on those parts. As for RPM, I personnaly have never seen a diesel engine regularily spin at 6,000-6,500RPM. My Mercedeswill cruise at 70MPH at 3,600RPM. It will hit 6,,700RPM if pushed My Honda will do about the same. As a general rule, diesel RPM are lower than a gas engine benefiting from higher torque at lower RPM than a gas engine.