any idea what the amsoil 5w40 "european formula" is made of?

 

I'm pretty sure its a PAO group iv, like the rest of the amsoil line except for the xl series which they state is group 3

 

Q1. How long do I need to wait before I change my oil again?

Follow the recommendations in your manual.

 

+1. 06 manual says every 3700 miles. What's with the 6000 mile interval?

 

Damn, I spend like $20-25 for 5qrt of 1 at walmart...

In my old FBody (i bought her new with 100 miles)... I did every oil change from day one full synthetic always, sometimes I would let her go 7,000 miles without an oil change. I sold the car at 165,000 miles and the engine was still in very good condition.

Don't get me wrong, that's not what I'm doing with the Z. Even though the book says 3750, I'm doing my synthetic oil changes at 3,000 miles never the less. Treat your car good and she will treat you good.

You don't need to use a synthetic filter. For the Z, I've been using the OEM filter straight from the parts center at the dealership.

Regardless, change any oil filter every time you change the oil.

Good luck...


Side Note:
When it comes to what brand of synthetic oil to buy, it's pretty tough to get actual test data because most of it is biased.

I'm probably changing from M1 to something else, don't know yet

 

Pennzoil Platinum has been working very good for me. I switched from M1 when I found out it wasn't fully synthetics, not only from this forum but others as well.

OEM oil filter does its job for me.

 

You're right, but the thread was about synthetic and all the synthetic labeled Amsoil lines are full PAO. The XL is not, although Amsoil doesn't say what is in their formulation on the cheaper XL line. With NOACK on the 30wt's less than 10%, I wouldn't be surprised if it were a G3+ / PAO blend on the base stock.
That's interesting that Pennzoil would offer an ester base stock oil to the main market. Still, as a G3+ like most of the synthetics on the shelves it has performed very well in the VQ. One of my favorite oils for normal drain intervals.
Will

 

Seems to be labled synthetic to me
Group 3 based synthetics are still considered synthetics ever since mobil lost its court battle against castrol. Its does say on their website that it is a group 3 based oil as well since 2002.
http://www.amsoil.com/articlespr/pr_2002_xl7500.aspx

 

So it is. Good to know.
I know a G3 is considered synthetic, it surprised me with all the marketing over PAO base stocks that they used a G3. NOACK numbers are very good then for a G3 base stock.
Will