Gang, In our modern cars, we use synthetics (Mobil 1 or Valvoline) all the way; anything older gets Castrol GTX or Valvoline non-synthetic. We briefly thought about trying a synthetic in our Rolls-Royce Phantom III's freshly-rebuilt engine (the only time you'd consider it for one of those) but decided not to do so for any engine featuring mechanical seals (even the rear main in the car's V12, dual-ignition setup is mechanical, no gasket, not even a rope seal). Regardless of recommendations, we change at 3,000 miles or Spring and Fall for cars that don't get many miles, such as the 4000-series Cobra or our R-code Galaxie, which both burn race gas and don't get that far from home. A simple plan, but with 24 cars, some of which are of the complicated sort, simple is good... Mike Heroy CSX4045 67 GT500 #841 68 GT500 #389 99 SP360 #81
