Well we have consistently seen GM engines do great on the few occasions someone has ran a 5W40. The reason GM engines like the old German made Castrol 0W30 was because it was aa thick 30Wt. as thick as you could make it and still be consider a 30Wt. this is why it performed so well. The 5W40 is still a 5W wich is all that matters interms of pumping,flow and cold starting etc...... The 40Wt. has a better HTHS and is going to do a better job keeping your parts from touching wich means less wear and tear. It is going to creat better ring sealing wich means more power and less blow-by wich means cleaner engine. The 5W40 has more anti-wear additives and better dispersant package then passanger car motor oil does since it is designed to hadle dirty diesels. I have not seen a single GM V8 that did not like RTS5W40. In fact I would say that RTS5W40 is for a GM V8 the same kick but combo as Redline 5W30 is in Toyota's! If this V8 has any oil consuption issues RTS will help reduce that as well. If my Toyota did fine at -30°F with Redline 5W40 that preety much rules out any winter starting problems for any one in the 48 United State in N.America plus Hawaii,and Purto Rico,American Soma etc...... In fact every application we have seen RTS 5W40 run in and a UOA done it has proven to do great from an old oil burning Saturn to an 18,000 Mile OCI in a BMW. WHen you look at it's performance and then look at it's price it probably the most under utilized oil on the market by this form in spite of it's great and consistent results!It used to be $12 a gallon but now is up to $16 a gallon at Walmart! Their is not any other oil that you can buy for $4 a quart full retail price that can go 18,000 miles in a BMW V8 and still have plenty of TBN left and low wear numbers and high flash point! If you tried to make it 18,000 miles with PP in that same vechile you would need 12 quarts of make up oil and the TBN and flash point still would not be that great! To get anything as good from the other big names like M1,Amsoil,RP,Redline would cost you a lot more and in your application I do not think they would do any better the only thing that would happen is you would be able to get them in 5W30 instead of 5W40. In my mind that like haveing to settle for a brunet super model girl friend when you had your heart set on a blonde super model girl friend. Not much of a comprimise is it?
