C'mon guys, can anyone really tell a difference between a 5W30 and a 10W30 synthetic during startup?
I have used a wide variety of syn and non-syn oils - Mobil and Castrol, and, while I fancy myself as very attentive and intelligent about what is going on in my engines, I can't recall hearing or feeling any difference.
I can tell you the difference between syn and non-syn on startup at -30F ... syn starts and non-syn doesn't ... try pouring 5 or 10W30 non-syn out of a can at -30F and then do the same with syn .... make sure you cold soak'em overnight outside. BIG DIFFERENCE! Mainly cause one is a lubricant still and the other is peanut butter.
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg