Originally Posted by
GTS Dean
Lots of ways to fine-tune your choice.
IMO, here are the pertinent factors to consider and my thoughts on them:
1) Conventional, or Synthetic? If you don't drive over 2000 miles a year and you think changing the oil every 3-6 months is right, then I'd recommend conventional oil. You're simply wasting money on ultra-premium oil.
2) Latitude and ambient temperatures: The farther north you live and drive, the more important the low-temp viscosity number is for cold starts and motoring. High temp viscosity rating of 30 is fine for northern latitudes and predominantly street driving. If you run it harder very often in the summer, or track once in a while, opt for 40. 10W-40 is my recommendation for most all southern latitudes and conditions. 40wt will handle moderate engine builds up to around 600hp.
3) Hot climates, high HP builds, heavy duty drive cycles/frequent track usage - 15W or 20W50 synthetic. However, if you change oil every couple of months, a premium conventional oil is just fine as well.
I used to track the hell out of my GTS with a stock power train in the hot spring, summer and fall in Texas and some occasional out of state events. I use Mobil1 15W-50 and add makeup oil as needed. I change it annually and sample with every change. With this extended drain regimen, I have found that fuel dilution becomes increasingly more noteworthy over 12 months and that leads to a reduction in high temp viscosity. It will also be harder to pass emissions (HC) if you are subject to a sniffer test.
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