I haven't tried the 5W-40, but I would assume so. The 5W-40 mid saps would probably work fine, but AMSOIL recommends the SS 5W-30. The SS has a lower volatility in addition to a higher TBN.Is the Amsoil 5w30 signature a better choice for this motor than the Amsoil European 5w40 mid saps?
They most likely did that for fuel economy purposes. I can't say that you'll have issues running a 40 weight oil. We have one guy who has been doing so. You'll run into is a fuel economy hit from the increased viscosity, but it will most likely be quite minor. Its up to you. Personally, I would run a 30 weight oil. It using AMSOIL SSO, 10W-30 would work great.I wondered because I use that oil in my wife's turbo car and keep it on hand. I am surprised that the small turbo engine of the cruze doesn't call for a 5w40 over the 5w30.