Reply to "What Oil to run in the Pantera?"

the 351C was originally spec'd for 20W40, 20W50 became the viscosity of choice when 20W40 was no longer available off the shelf. Living in a climate that is much colder in the winter and much warmer in the summer, I would advise you to run a lower viscosity oil in the winter, higher viscosity in the summer.

Having been inside many engines over the years I can generalize and say that Valvoline leaves a grey residue inside engines, Pennzoil leaves a gummy brown varnish, Castrol leaves the engine clean (assuming regular oil changes).

Synthetic make sense for new or rebuilt engines, if you want to avoid wear. I have seen bearings come out of engines running sythetic oil that looked like they were new, out of the box. Synthetics also leave the engine clean inside and are far superior at elevated temperatures. Running synthetics in my own vehicle, I have seen oil consumption get better with mileage, a 100,000 mile car getting better oil consumption than it did when it was new! There is less or no carbon build up in the piston ring grooves.

Viscosity stabilizers tend to break down with use, I prefer to use oil with less viscosity stabilizer (10W30 as opposed to 10W40). Amsoil marketed a 20W50 synthetic oil that had no viscosity stabilizer in it, it was "naturally" 20W50.

Byproducts of combustion pollute synthetic oils at the same rate as mineral oils, so the idea that synthetic oils don't require changing as often as mineral oil is bogus.

Finally, if you're going to spend the bucks on synthetics, buy one that uses a synthetic base (100% synthetic), not one that uses synthetic additives to a mineral oil base. Mobil 1 sued Castrol in Federal court about a decade ago because Castrol was claiming their oil was 100% synthetic when in reality it used a mineral oil base.

George