Thanks MikeW for seeing my point - there is not alot of difference in finished performance between conventional API products.
G-Man and FlimFlamm
Here's another reason why to use a higher quality oil than conventional. I purchased one of my 'gotta have cars in my life' back in October 2002. A 36,000 mile, original (stock) 1994 Twin Turbo 'God it's still sexy today' RX7 R2. In fire engine red. From a friend who build's V-8 circle track engines. One owner car that always had the oil changed every 1000-1500 with Castrol GTX.
The car is nice. Passed emissions (yeah, the EPA god's play havoc in Houston)with flying colors recently using the oil and filters as purchased. (It's a third vehicle, well actually fourth - okay seventh if you include all the others including the two race cars and the one being restored)
Well, I wanted to get a baseline on the car's stock performance including the conventional oil and then start documenting performance upgrades.
The usually stuff, catback, K&N, bigger intercooler, more boost, more power!)
Changed to fresh Castrol GTX, oil filter, air filter, coolant, coolant hoses, plugs, wires, etc to make it a fair baseline rather than runnning on oil that had 1000 miles on it.
Couldn't get the chassis dyno (at a Porsche shop) to repeat. By the third run, the exhaust was emitting oil smoke on deceleration. By the fourth and fifth, the oil carryover into the intake was apparent.
What happened you ask?
The conventional mineral oil, that many call 'dino' (sic) oil, allowed the oil seals on the secondary turbo to get hard and crack. Under the hard pulls on the dyno at full boost (10,8,10 psi typical boost pattern of a third gen RX7) the oil was being blown into the intercooler and intake to where it was pooling in the throttle body - I know because I checked) The previous owner did not abuse the car. He changed the oil every 1000-1500 miles using the 'vauted' Castrol GTX but it did not have sufficient high temperature protection against thermal breakdown. (hmmm, sounds like something out of a commercial).
By the way, the car still runs great on the street but until I swap out the turbos, it won't get any long term high boost runs. But with the frequent oil changes IF the mineral oil had been sufficient, these seals should not have failed.
IMHO, the early failure of these seals is directly related to the lack of high temperature performance of conventional oils.