Based on your premise, I would recommend GC as it is a thicker 30 wt. While avaiability is an issue with GC, it appears that at Autozone at least, Mobil 0W-30 is going to become just as scarce as the Elixer of Tibological Triumph.quote:
Originally posted by AEHaas:
Going from a 40 wt to a 20 wt may be too big a jump. Try a 0W-30 first. I would try Mobil 1. That car has a lot of miles and may NOW require a thicker oil. If the car NEEDED a 40 wt oil for the first 450,000 km then it may actually need a 50 wt oil now.
Certainly it is worth experimenting. Put the 0W-20 Mobil 1 in there and send me the operating pressures at 2,000, 3,000 and 4,000 RPM at full (normal) operating temperature. First collect the same data with the old oil under the same conditions for each oil. If the 20 wt oil flunks I will buy you the next oil to try, the 0W-30 Mobil 1.
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code:
Lead 1 Calcium 2000+
Copper 2 Zinc 911
Silcon 38 Phosphorous 806
Iron 9 Manganese 88
Aluminum 1 Magnesium 34
Viscosity (100C) 8.725
Solids (% V/V) 0.1
Fuel Dilution YES
Glycol NO
Water (% V/V) 0
Base Number 8.80
Well, it saves you all the intermediate terrain if the stuff is functional for you. You will either learn that it does work or it doesn't. It's no more or no less valid a manner of figuring out the right grade. I would highly doubt that your engine is going to spontaniously self destruct. Since you're using UOA ..you're not doing this blind.quote:
You guys are probably right.......sometimes it is good to push the envelope however.
AEHaas,quote:
This articles show that the piston-ring seal is best with thinner oils. The oil film thickness is actually greater.