You are exactly correct! When talking trucks or motorhomes, people often comment on the maintenence cost difference between diesel and gas. The gas engine uses 6 quarts and a $6 oil filter that you change every 3,000 miles in rough service. The truck diesel engine takes 6 gallons of oil and a $20 oil filter and at least one diesel filter (usually 2) at around the same cost each, but is changed at 15,000 miles. The actual cost difference is not significant unless you drive just a few miles and resort to the annual oil change at something like 5,000 miles, in which case the gas engine was far cheaper to maintain. Point is, you can certainly get good life from petroleum oils, but you do need to examine your usage to figure out what fits your needs. Stan
Old School said:ndnparts that's a excellent point!
In my initial post you will find a reference to filters. Take a look at the filters used on CAT and Cummins, more than likely it's made by Donaldson Corp, maker of some of the best filter you can buy, and is four times the size of a regular filter, has a efficiency rating two to three times that of your car. Also the volume of oil held in those engines is greater so the same oil takes longer to be cycled back through the motor. This is one of the reasons the over the road semi doesn't need to change its oil as often.