All, I've been using Shell Rotella 5W-40 T6 full synthetic for motor oil and so far I have had excellent results. I switched out air filter from OEM to UNI, drilled the upper/lower rear A arms and tapped in zerk fittings...front will be next. I've been using OEM oil filters, and since the TPS adjustment, engine braking actually works. Swapped differential oil with 80/90 LE fully synthetic........Any other improvements that you folks are doing on the older 500 HO EPS I may have missed?