[Texasoil]

I , like Bob the Oil Guy, have lots of good technical experience in the lube oil field. Modern 10W-30, 10W-40, 5W-30, etc oils have a very high percentage of the very same molecules as the heavily advertised 'synthetic' oils. AMSOIL and Royal Purple ARE significantly better.

Under the right conditions, extended interval oil changes are OK--but WILL NOT meet the requirements of the manufacturers warranty. You MUST change oil and filter at/before the mileages/time recommended by the factory AND keep a written record and receipts or the manufacturer will tell you NO if an internal part fails--for any reason.

Oil is so cheap compared to fuel, tires, etc--why take the risk of major wear and deteriorating by stretching change intervals. Do the math. If you do 4000 mile changes at a 'quick lube' at $30 a time, that is a whole $720 in 100,000 miles. That cost is less than 5% of the fuel cost. The noise about running smoother, etc is B.S. Toyota is fanatical about reducing engine noise and vibration. If Royal Purple oil (or any other magic elixir) provided improved smoothness of operation, THat is what would be in them from the factory and REQUIRED as a special Dealer only product, just like the ATF for some vehicles is Dealer only avilable.

Lower viscosity oils reduce friction and improve fuel economy--at the risk of allowing more metal-to-metal contact and resulting wear. Oil is CHEAP, hard parts are EXPENSIVE.