I guess I'm the first vote for Castrol, but only GC.

Bought 42 quarts of the stuff in the fall so I'm running it from now until roughly 2012.....

 

The consensus is that among the M1 oils, the only weight which is Group IV base stock is 0w-40.

 

I run M1 15w50. Live in Phoenix so hot is way more of an issue than cold. Takes a while to warm up so remote start helps and I would not go that thick without a temp gauge.

 

Just 0w40 and thats all.

 

Rotella T-Synthetic 5W40.........it a super oil (and it is inexpensive.) I'll let my Used Oil analysis tell the story. I think it pretty much speaks for itself!!!! (my 1st sample was with Motul 300........don't waste your money.) The Rotella is awesome stuff. Very high ZDDP additive package in it. This oil is taking care of my motor nicley. I've had, nitrous, single turbo, and now twins on this engine for over 3 years..........and the wear metals are super low on this engine. (the high lead in previous samples was due to a tank of race gas about a year ago.) Have a look at the UOA from Blackstone Labs, and then ask yourself why you'd run any other oil in your VQ?

 

If you have a 2005 + vehicle, look in the owners manual and you may find that it requries an up to date API SM rated motor oil to maintain the warranty. If you look on the bottle of RP 5W-30 or 10W-30, you will find it is an older API SL rated motor oil from 2004, which means it is for 2004 and previous vehicles as the back of the bottle states.

 

Where are the TBN numbers so we can evaluate the oils additive package?

 

Not from what I read, relative to the 2005+ vehicles.

Quoting directly from the owner's manual of the 2008 G35, page 9-6:

"It is essential to choose the correct grade, quality, and viscosity engine oil to ensure satisfactory engine life and performance, see "CAPACITIES AND RECOMMENDED FUEL/LUBRICANTS" earlier in this section. Infiniti recommends the use of an energy conserving oil in order to improve fuel economy.

Select only engine oils that meet the American Petroleum Institute (API) certification or International Lubricant Standardization and Approval Committe (ILSAC) certification and SAE viscosity standard. These oils have the API certification mark on the front of the container. Oils which do not have the specified quality label should not be used as they could cause engine damage"

The bold of "...improve fuel economy." was mine.

So that being said, it doesn't say that using a non-API SM rated oil will void your warranty. Also, it appears that one reason to go with API SM rated oil may be better fuel economy.

From what I'm reading about API SM rated oils, the SM rated oils are, quoting from the API Engine Oil Guide, "For all automotive engines currently in use. Introduced in 2004, SM oils are designed to provide improved oxidation resistance, improved deposit protection, better wear protection, and better low-temperature performance over the life of the oil. Some SM oils may also meet the latest ILSAC specification and/or quality as Energy Conserving"

The API Engine Oil Guide is available at this link:
http://www.api.org/certifications/en..._Oil_Guide.pdf

So, the difference between the SM and SJ rated oils appear to be better additives to protect against oxidation, sludging, wear, and low temp performance.

Now GC is rated SJ/SL but not SM. Yet, it's UOA's have shown that it is a very good (if not the best) oil for the VQ35 in the G, along with M1 0w-40 (which is SM rated) but is out of the recommended viscosity range.. Yes, I know the M1 0w-40 shears down quickly to a 30 weight, but I'd prefer to not get into a debate with the service advisor/manager hence my decision not to use M1 0w-40 in my G.

If anyone can correct me, please do as I have an 08 G35 and want to make sure it gets the best oil possible, without breaking the bank.

 

Well it's 2:30 AM and the toothpicks under my eyelids are bending, so I'll be brief at this time, but I think if you investigaged further with the vehicle manufacturer, (which means not the dealer), you may find the vehicle manufacturers wanting their new under warranty engines to be using the latest API rated oil, (which in this case is SM), rather than an oil from 5 years ago, with the older SL rating. The RP bottle even warns against this on the back, I'll give them that much.

 

I'm quoting directly from the owner's manual so I'm not listening to some service advisor/manager.

If I'm wrong with respect to the SL versus SM rating, please correct me. Also am I incorrect to state that GC has gotten very good, if not excellent UOA's in the VQ35s to date?