The big rig 18 wheelers around here hold 40 quarts with a 4 quart oil filter. I changed two trucks with 75,000 miles on the oil.

 

Synthetic lube is great in any engine, old or new. Mobil 1 synthetic is factory fill in the Corvette and many other high performance cars. Running new engines on synthetic oil is no problem, the engine will break in just fine. Synthetics are superior in extreme hot and cold conditions. In the cold the lube flows like water compared to petroleum lube that will barely pour out of the can in sub zero conditions. Obviously this will provide much better protection in extreme cold. In extreme hot conditions petroleum will carbonize and provide no protection but synthetic will continue to provide protection. I also use Mobil synthetic lube in all my greaseable joints and their 75w-90 gear lube in my differentials. Most people report improved fuel mileage when changing to synthetics. Obviously that is from reduced friction and friction is a bad thing! I personally have noted as much as 1 1/2 mpg improvement when changing to synthetics in my 4WD pickup.