Originally Posted by Nederlander75

It’s the Viscosity Index Improvers that pose the risk from what I understand and the broader the spread the more there are. A 5w50 is a spread of 45 versus a 15w50 that’s a spread of 35. The 5w50 requires more VI improvers to keep its viscosity at higher temps since its starting from a thinner base stock. Therefore, in my opinion if you are running the 5w50 these VI improvers will be sheared (torn) apart such that you will be sacrificing protection with prolonged use as your 5w50 may end up shearing to below a 40wt. In your application that loss of projection may be detrimental if not destructive on the track or if you are beating on the car. Conversely, I’ve heard that M1 15w50 and others may not contain any VI improvers making them much, much less prone to shear. So, you can get more life out of that oil and be safer on the track. You just need to ask yourself or figure out if you really need 50wt projection in winter. If not you may be able to live with a little shear or a 5w40.

Originally Posted by 350zzzgunnar

Guess I'll go for a M1 15w-50 since the car hibernate in the garage during the winter. Or do you have a better suggestion for choice of brand?

Originally Posted by Nederlander75

Im sure M1 will do ok, but there may be other options available that might be better. What brands to you have access to? Fuchs, Amsoil, Shell, Royal Purple, Redline, Motul, Quaker State?

Originally Posted by 350zzzgunnar

We've got Shell and Redine for shure, the others I've never seen but I'm a oil-retard

Originally Posted by IP05G35

Be on the lookout for my UOA pretty soon on my G35 running Mobil 1 0w-40 for ~8000 miles.

Originally Posted by ZeeForce

^^ Ditto on that...I am also running Mobil1 0w-40 on my 05, but only have 4135mi...oh wait, it's time to change oil soon. My plan was to change it at 4400mi. Thanks for the reminder.

Originally Posted by JETPILOT

With respect to the MOTUL UOA reading high in lead... if you run leaded race gas your going to contaminate your oil with lead. I think Quad ran race gas when he was using the MOTUL. As far as iron... I imagine that is from the cams. Why? I have no idea. Aluminum.... that has to come from the head/valvetrain I imagine.

I am going to be using MOTUL in a few weeks after my motor is broken in and I will send it to Blackstone to get an UOA.

I don't think we can draw any conclusions about MOTUL yet. There are just not enough UAO's. BUT the series 300 racing oils exceed the standard for API-SH which indicates a very high level of ZDDP.

ZDDP which is an anti wear additive (zinc and phosphorus) has been reduced in newer oils because of it's ability to contaminate catalytic converters. You can find high levels of these additives in API SG-SJ with the minimum rating used being SL rated oils. So the oils falling under these classifications are likely the best to use for reduced wear although having short drain intervals (3000-5000mi).

Since extended drain intervals are not what we are looking for in an oil we should consider sticking with API SE-SJ rated oils instead of API SM or SL/AEPA CJ-4 rated oils.

API SJ rated oil meet the new ACEA A3/B3 European requirments for acceptable wear during testing which is approx 1/4 the wear allowed with the new API SM or CJ-4 oils (Rotella T). Rotella T is now an API CJ-4 oil and the additive package in this oil seems better suited to keeping emissions controls happy than to protecting the engine. Rotella T was a CI-4 oil, but has been reformulated as a CJ-4 oil and the addative package is not as good. If you can find the CI-4 then stock up on it.

Another great oil is the Amsoil Series 3000 diesel oil. It has high amounts of ZDDP and is API SH/CI-4 approved.

Our owners manuals state to use API SG/SH/SJ/SL. We should not stray from these designations/addative packages since that's what the bearings, valvertrain etc. were designed for.

Here is a great article about the changes in additive packages mainly concerning ZDDP. These changes are being fueled by tighter EPA restrictions not to the benefit or the longevity of your engine.

http://www.lubrizol.com/press-room/m...ate+Thickeners

JET

Originally Posted by Resolute

A couple of guys have wondered where my Rotella T-Syn report is. I am still running this oil. I'll get it analyzed in a month or so, which means it will have been in service for about a year, but only 5k miles.

Nederlander75 asked a question about the base stock that Shell uses in their T-Syn, which is a slack-wax base stock derivative. It's also known as Shell's XHVI base stock, and is used in other formulas of oil, such as their Helix Ultra.

Shell's XHVI base stock, which is a Group III oil, is made by the hydroisomerization of slack wax, as opposed to most other Group IIIs, which are hydrocracked crude. Slack Wax is a byproduct that is formed from a solvent process, but what Shell uses is a synthetic slack wax feedstock made from the Fischer-Tropsch method. The Fischer-Tropsch method is how the very first synthetics were made, and is the method behind Gas-to-Liquid (GTL) base oils as well. So, Shell's XHVI base oil is made from the hydroisomerization of their synthetic slack wax which is developed through the Fischer-Tropsch process.

Slack Wax oils have a VI of >140 and perform similar to a PAO in almost every way. Cold Pour Point is about the only area where common PAO's have a meaningful edge- about 10 degrees lower on average.

Will

edit: broke into paragraphs for easier reading