I am in the PNW, I usually use Rotella Synthetic 5w-40 year round, $14 per gallon at Walmart. I had less consumption than I did with Mobil 1 10w-30 on my '93. They didn't have Mobil 1 5w-40 available when I had my '93, but they have it at walmart in 5 quart jugs for ~$20. I have only done one oil change on my '96 and used Rotella Syn, I considered trying the M1 5w-40, but haven't yet.