I'm using Rotella T6 5w40 in my flat tappet motor at the moment. In the past I've used M1 HM 10w40 and QS Defy 10w40.
After my rebuild I tried 5w30 and 10w30 but was worried about the zinc levels and didn't want to buy break-in additive every time. I think the engine ran noticeably quieter and smoother on the 40 weight.
After my rebuild I tried 5w30 and 10w30 but was worried about the zinc levels and didn't want to buy break-in additive every time. I think the engine ran noticeably quieter and smoother on the 40 weight.
