I believe that's cause most places only stock the 5w-30 and 15-50 or at least that's the only Mobil 1 extended performance I've seen. I know they make it.
http://www.mobiloil.com/USA-English/...rformance.aspx

 

this might raise a couple eyebrows, but i use a mix. 50/50 synthetic and dino. read a while back smokey yunick (i hope everyone knows who he is) tested it and got the same results as a full synthetic mixing it.

 

As far those who use Amsoil what filters do you use? Also what exact Amsoil would you want to use given a climate such as florida or vegas? Lastly any reason everyone doesn't use amsoil if its the only genuine type 4 ( or so i've speed read on this thread ).

 

I ordered the AMSOil filter as well but was told the oem does just as well.
I ordered the 10W40, I'm in LA not quite as hot as florida or Vegas but it gets up there.

Why is not everyone using it?...in my case you can't buy it in a store here and have to order it and it's taking the AMSoil people forever to ship an order...I ordered mine a week ago they just finally shipped it on Friday.

 

Ah ok I have no idea I actually never heard of it prior to yesterday but was told it's the best. Thanks for the info.