I come from a land downunder 20W-50 reigns supreme. Anyway, back during the REAL thick/thjin debates, I ran a 20W-70 over winter (-7C) and had nothing much to report other than a 3MPG drop over the 20W-50. Then ran 30weight over half a summer (sold the car, and they ran another 20 months on the Pennz HD30 without my knowledge). Since BITOG, I have accepted 40 weights, without losing my thick heritage. I'm on 6 month oil changes on my 4Runner (12 months on M1 0W-40, short trips, and 2500km convinced me that was wrong). I'm thinking that cold months are coming, and Pennzoil 10W-30 SL is $2/L cheaper than Delo400. I'm thinking...of using...my first...ever...30 weight multigrade. And not for experimental purposes, 10W-30 winter, and Longlife Summer.