I've got a Stillen Stage 2 S/C kit in currently, soon to be stage 4 once I can get the parts in. I saw another thread about motor oil, and realized I don't know why it's something I never thought of changing when I went F/I. I'm still currently running Amsoil 5w-30 synthetic. Is that gonna be a problem?

I'm not looking for a discussion of different motor oil brands so much, but rather a discussion of what weights I should go with. What viscosity for cold and operating temps?

?w??

 

i run royal purple 5w-30 all year and i live in va. i love this motor oil. no you need to run full synthetic all the time with a sc. i'm pretty sure that you shouldn't differ in what weight your running right now.

 

i run 5-30 mobil one in the winter months and 10-30 mobil one the rest of the year.

 

What's the reasoning behind running 10w30? I understand how weights and viscosities work, but I'd like to hear your reasoning.

 

Anyone? I was thinking about maybe 5w-40, but wanted to see what other people are running, and the logic behind their choices...

 

Since you're running more heat in your engine, a oil with a higher HTHS is going to be your best bet. I don't recommend the Amsoil 5W-30 that you have because all the UOA's that have come from VQ's have shown remarkably high lead content after use, which is a sign of bearing corosion. Also, it's HTHS is only 3.09. It's a good oil, but not for a boosted Z. I would stay away from the Royal Purple 5W-30 grades. They are really thin for a 30wt oil with only 10.7 to 11 Cst @ 100 deg C. My recomendation for you:
Over the counter Oils: try M1 0W-40, German Castrol Syntec 0W-30, or QuakerState Q Advanced 5W-40. All have very good Cst @ 100 deg C and very high HTHS numbers-
Mobil 1 0W-40 @40C 80 @100C 14.3 HTHS 3.6
QuakerState Q European Formula 5W-40 @40C 90.5 @100C 14.5 HTHS 3.9

For designer label oils, maybe give Amsoil's series 3000 a shot, it's a lot thicker at temperature than the 5W-30. Or Motul 300V 5W-40:
Amsoil Series 3000 @40C 64.6 @100C 11.5 HTHS 3.5
Motul 300V Power 5W-40 @40C 80.8 @100C 13.8 HTHS 4.51

Any of these will flow well enough when cold, and protect a lot better and longer than what you've got in there now. They also all have very good UOA results to back them up.
Will

 

I use Mbile One 10-30 all year round

 

I use a 10w40 all year

soon I will be trying the Motul 15w50 though

 

As everyone's recommend lately, the German Castrol syn 0w.

 

I run straight 30 wt with no problems all year long, the climate of southern california allows that. Multi viscosity oil's ability to change viscosity is created by adding a polymer to the blend. As the oil heats up the polymeres unwind thickening the oil. If you want or need to run a multi oil select one with a close ratio like 10w30 or 20w40, the closer the ratio is the less polymere. Under extreme loads the polymere will break down quicker thinning out the oil.

Here's a good read http://www.repairfaq.org/filipg/AUTO/F_oil_facts.html

 

That's not true. VI modifiers do not have a detrimental effect on most oil's TBN or Cst anymore. Look at the numbers. There's nothing to support your claim that the closer the winter grade is to the temp grade the more stable an oil is. In fact, M1 0W-30 has a higher Cst and TB than 5W-30, with 0W-40 beating both of them. Comparing grades is not enough, you need to look at the formulation, base stock, and the Cst numbers.
Will