gordgee & gsedanman: interesting. I have the manual that doesn't mention synthetic. I wonder which manual came first. What's the printing date (on the outside back cover) of your manuals? Mine was printed Aug '02.

2003.5 G35 Sedan Desert Platinum/Graphite Premium/Sport/Aero/Nav/Winter

 

Conclusions from posting page 10-5 for the Sedan and the coupe
Sedan: mineral or synthetic
Coupe: mineral only


I'd venture to guess that even though it's the same VQ motor between the coupe and sedan, the tuning differences of the coupe (the extra 20 bhp) for some (odd) reason mineral-based oils keep the motor more reliable than a PAO-based oil.

Anyhow....I'd say Castrol Syntec is the best compromise....these days as hydrocracked mineral oil improves in technology, as does performance. Many argue that hydrocracked mineral oil base stocks are near PAO in performance, but cost much less.

 

just a little FYI...i've got 4100 miles on my 6M coupe...taking it in tomorrow for the first "service". Spoke w/ the service manager today and he said they would provide the synthetic for my service tomorrow for free...so I assume I'm covered...and I'd rather have the synthetic since I drive like a maniac anyway.

 

Regarding page 10-5, I have a Sedan, and my manual doesn't mention synthetic. My manual does refer to both the coupe and the sedan.

2003.5 G35 Sedan Desert Platinum/Graphite Premium/Sport/Aero/Nav/Winter

 

Any engine will benefit from synthetic oil. As far as it being a waste, keep in mind that the better non-synthetic oils ($3-4 a quart) are still good for only 3500 miles while fully synthetic oils ($5-6 a quart) are good for 7500+ miles. After a few oil changes, which option is actually more expensive? I'm not talking about the $1.20/qt oil, either... that's the stuff I call "new engine break-in oil"

Typical dino oils at 3000 miles will have bigger score marks on the test cams versus Mobil 1 TriSynthetic and Amsoil at 10,000 miles (all with equal viscosities).

Modified engine or not, our modern engines have closer tolerances, higher redlines, and more complex valvetrains, so it's natural to assume we will need the characteristics of a good full synthetic.

One more thing to mention, cross out the 3500 where you see "oil change intervals" mentioned in your manuals. If it's a non-turbo vehicle, a fully synthetic oil is still good beyond 7500. I change my oil at the 7500 mark on all of my vehicles. If it's a turboed engine, that number falls back down to 3000-3500 because the turbo's are very hard on the lubrication.

 

primerAL, I use almost the same intervals as you do. I tend to let RedLine stay in longer but that is just me, Amsoil is just as good as Redline or Mobil1. I generally don't like to leave oil in for longer than 9k on my Chevelle though. It tends to heat a bit in traffic. Good info though and I am glad that others here feel as I do. Some think we're crazy to leave oil in "for that long"..."egotta be every 3k on the dot"

03.5 Sedan/B. Silver/Premium/Winter/Aero
69 Chevelle BB/4.11's

 

If you want to use synthetic, and eliminate the guesswork involved in determining your oil change interval, the best method is through oil analysis testing.