what's the difference between amsoil 5w30 xl and asl?

 

Their website will tell you the difference. XL is extra long life, other is not.

 

that would be incorrect, XL is actually their cheapest worst oil, and is marketed towards oil change shops. Its a group 3 based synthetic while ASL 5w-30 is a "true" synthetic and is group 4 based. TSO 0w-30 is their top of the line oil and works great in the VQ

 

why is 0w30 better than 5w30?

 

5w-30 is like 5 weight oil when it's cold, and 30 weight when it's hot. Which basicaly make your car start easier because the oil is thinner when cold.

If you look at the back of the oil bottle it will give you a guide for the temperature range you live in.

Realy cold weather 5w-30
Realy, realy cold..0w-30
California weather 10w-30

 

I am aware of 0W-30 from the sticky, thanks. I stand corrected on the XL. Since it stands for Extended Life, I assumed it to be so.

 

is the TSO a better formula then the ASL? because i know i don't need anything lower than 5w

 

TSO 0w-30 is not necceserily better than ASL 5w-30 even though it's more expensive. Both are group IV PAO based oils but the TSO has a proprietary ester additive package (it uses no moly or born like ASL). In my opinion up to 10,000 miles they provide the same protection but after that if you want to extend to 12-15,000 miles the TSO is better. I don't know of anyone with a G35 or 350z that does that though. My local shop that sells Amsoil sells the ASL and the TSO at the same price (8 bucks a quart) so I got the TSO right now. The XL line uses almost the same additive package as the ASL but it is group 3. It's an excellent oil for the price. I would say the XL 5w-30 is a bit better than Mobil 1 5w-30.