[Duc Hunter]

I have always found it interesting that back in the day Porsche was ok with a 40w straight weight oil of the hottest temps, and a "fuel efficient" multi weight 10-40 for hot temps. Interestingly they also show a 20-50 for the hottest temps in multi-grade, and 10-50 for lower temps than a 15-50 or 20-50. So which is it? Can a 10-40 handle the high ambient temps and potentially lower oil temps as its thinner oil, and we know thicker oil raises oil temps? If we can run a 40w straight at hot ambient temps why not a modern 10-40? As for the 15-50 vs 20-50....I thought the lower number was for the color end of the ambient temp range and had no effect on the top end? I'm so confused! LOL

Here in Florida it's in the 90's all summer and humid, in the winter we don't see freezing. The means a 10-50could be perfect. Porsche air cooled oil is 10-60, which doesn't even show in those old manuals. My 3.6 runs cool, my 3.2 always runs warm. I have often thought of swapping down in weight to see if it help s any in the 3.2. We also need to remember that that chart is from an 80's manual, and the other manuals posted are from the early 70's. oil has changed a lot in that time (good and bad).