A manufacturers oil recommendation is exactly that it does not mean you will cause damage if you change the weight. 5w30 and 5w40 are very close ask any competent engineer or mechanic if switching between the two will cause problems it Wont!I It is a common Fact many people change the weight of oil due to several factors including weather the age, mileage work load etc.of any given engine. Once again ask an engineer or mechanic, myself and millions of others have done this countless times on tractors trucks cars buses HHRs bikes etc, with NO problems! Lucas and STP are just 2 examples of Thick additives used in engines. I have done real world experiments with all sorts of engines Never have i had Any problems related to changing the oil weight nor do i have any problem passing on my Experience and others on how to get better mileage! Thousands of Trucks and Cars run thicker 20w50 oil in the summer and 10w40 in winter months or other weights and yes i know (w) does not mean weight but viscosity at different. ambient temps. My personal HHRs have used 5w-30 5w-40 10w-30 and 15-40 oils again No problems. My point of this is closing a thread based on mistaken Opinions without facts is wrong. I stand by my statements from Actual Experience in the Real world and talking to real mechanics and engineers! 5-40 Rotella T6 synthetic gains about 2 MPG!

 

Are you taking into account the Ecotech engine's high reliance on oil viscosity to control things like VVT?

I think Rotella oil is formulated for diesel engines?

You can run any oil you like in your vehicle, the problem comes with recommending others use an oil that is not approved by the manufacturer; in this case Dexos 1 or 2 specification 5-30 weight.

Recently we have had members come with VVT problems from using "old school" oil and additives. "My grandfather always used 15W60 in the summer and 10W30 in the winter".

The competent engineers I know all say "if close was good enough, I wouldn't have a job."

 

Drifter.. if you cannot accept the reasoning behind closing that previous thread as well as the explanations given there, and here, perhaps this isn't quite the right forum for you.

I too have used non-recommended oil in years back in the 60's and 70's, even the 80's, but there is no way I would recommend anyone doing so.

This thread too is closed.