Was wondering if anyone in the southern states is using the 0w-30. Our heat index has been reaching 110 lately. They used to advertise a chart that showed what weight was good for a certain temp range but could not find it ....thanks ahead of time...
Fortunately car engines don't care about heat index. As far as outside temperature goes, all that matters is actual air temperature. Unless people in the desert SouthWest are having premature engine wear and failures on 0W-20 it should be more than OK in the South. That said, 0W-30 will do no harm and may buy you enough piece of mind to make it worth the small mileage hit. Also, 0W-20 oils tend to be on the thick side of the SAE 20 viscosity spec and 0W-30 oils tend to be on the thin to medium side of the SAE 30 spec, so it's not like you are really a whole grade thinner than a 0W-30.
If you want a "thick" 0W-30, consider the made in Germany Castrol Syntec 0W-30. It tests out on the thick side of a 30 oil, which is why it doesn't carry the fuel conserving label The difference between most mass-marktet xW-20 and xW-30 is fairly minor If you are concerned about the impact of very high temps, a used oil analysis will help. High temp and high load operation will cause the oil to breakdown in a very specific way.
I have had the same oil in since May (Mobil 1 0W20) and will change it out at 10K miles in Sept and have a UOA done. It gets pretty hot in this part of Oregon, not like Phoenix, AZ but quite a few days over 100 F. I do a lot of freeway and mountain driving so maybe we can learn something. If anyone wants the German Castrol Jayman mentioned I think the VW/Audi dealers sell it. Apparently you can get it at Auto Zone also, just be sure it's the German product not the made in USA version.
Yeah use 0W-30 if you want to void your mfg warranty. The manual specifically states 0W-20 and nothing else. Extreme heat outside doesn't matter with oil. It gets to hundreds of degrees inside the engine. Only in extreme cold will the weight of the oil have some bearing on lubrication.