Most modern synthetics don't need VI improvers anymore though, even in 5w30 form. The quality of the base oil has a lot to do with it, as a good base oil can give you the required cold cranking numbers in order to qualify for 5w status.
Take Redline for example, they claim the only viscosity of their oil which uses VII is their 5w40, and it's only using a little bit of it. The rest of their oils use no VII at all. With the base oil they run, they don't need them.
I'm using a 0w30 oil myself, the German made Castrol Syntec (known as Formula SLX in Europe) This oil has proven itself to be very good, I've been using it in various cars for a few years now, and it always shows very low engine wear numbers in oil analysis. As a matter of fact, I've never seen an LS1 engine with better wear numbers than my recent oil analysis report using this oil.
Here are the results:
5000 miles on oil
Aug7-Oct 11 (2 months)
37,000 miles on engine
German Castrol Syntec 0w30
K&N oil filter
K&N air filter
Daily driver, lots of full throttle
9 quarter mile runs, 10 dyno runs
7L oil capacity
no top up oil
DIC said 39% oil life left
Iron 8
Lead 1
Aluminum 3
Copper 2
Chromium 0
Nickel 0
Titanium 0
Tin 0
Silver 0
Vanadium 0
Silicon 7
Potassium 0
Sodium 0
Boron 5
Barium 0
Manganese 3
Calcium 2419
Magnesium 101
Moly 26
Phosphorus 737
Zinc 831
Sulfur 2420
Oxidation 56%
Nitration 39%
Sulfation 42%
Fuel 0
Water 0
Glycol 0
Viscosity 11.5 cst at 100c
TBN 6.2
To say I'm happy with this report would be a major understatement! I am extremely impressed with this oil! I figured the first run would not be anywhere near as good as this, and I did not expect the K&N air filter to do so well. It's definitely staying in the car! I'm also happy to see the copper so super low! I guess not all LS1s put out tons of copper for a very long time. I fully expected to see 50-60ppm there.
Compare this report to any other synthetic oil out there, including Mobil 1, and you'll clearly see this oil outperforms them! European oils must pass stricter tests, which is one of the reasons why this oil is so good. Based on how well it maintains it's viscosity, the experts I consult with believe it contains little to no VII in it. It simply uses a very high quality base oil (which is fully synthetic, unlike the American made Syntec)
