in my 2005 Audi 4.2 V8 automobile? It appears to be a diesel oil. Any harm in that? The warranty is up (50,000 miles) and the free oil changes every 10,000 miles are done. Might be a good thing as I think the dealer uses 0-40 M1. I think it breaks down too quickly in this engine as I had some startup noise issues prior to the last change. Timing chain is tensioned by hyd pressure, since the change, no more noise. Might have been a breakdown in viscosity. I was surfing this site this weekend and think I would like to use the 5-40 from Schaeffers or even wondering about the Shell Rotella T 5-40. What about going down to a 30 wt oil to pick up fuel mileage and power? Any 30 wt. recomendations that may go 10,000 miles to a change? Any help or sugestions appreciated!