Quote:
Originally Posted by canis
Haha, amazing isn't it, how experiences vary. Apart from a few commercial vehicles, I've always run petrol cars. And I've yet to find one whose oil doesn't turn black, or at least very dark brown. On the dipstick it looks golden, but put it in a jar and it's nowhere near as transparent as when it went in. I usually change mine annually, and I've been using 10/40 semi-synthetic.
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Nearly all modern petrol engines are design spec for some kind of Xw20 or 30 grade.
Volvo only listed Magnetec 10w40 as OEM dealer spec (Not the same as design spec) because it was OK for any of the V40 engines.
10w oils have a cold pour point of around minus 25C and that means that they should not be used for cold starts below minus 15C, as that is the temp when the slower oil flow and increased oil filter bypass time results in more main block wear (Not good for the turbo bearings in particular). Above that temp the only real issue is how much more effort is required by the battery and starter motor during cold starts.
Most newer cars have weaker starter motors and smaller batteries than they did in the old days, as they are easier to start due to modern ignition or injection systems. The use of 0 or 5wX oils also reduces the electrical loads during cold starts.
If I had a petrol V40, I would use a major brand full synthetic 10w30 longlife oil during the summer and an 0w30 during the winter.
A 10w30 will last longer than an 0 or 10w40 in residual viscosity terms, cos it contains less viscosity improver (VI) additives. Those additive are a negative factor in resisting high temp shearing of the oil in the turbo bearings in particular. That means the oil with the least VI's will not thin out as much, so can be used for longer IF it contains enough detergent additives and it not subject to too much fuel, Silicon (Bad air filters) or anti freeze contamination.
Many good 10w30's finish up thicker than 0w40 oils at the end of a typical 5 to 10K mile OCI.
Most petrol engines can use 0 or 5w20 oils during the winter if the OCI is not too long. The 0w20's are used a lot in the USA to help fuel economy figures, but I would not use them during the summer, particularly if you have a big right boot or tow a heavy box or caravan.