I know GC and Mobil 1R 0W 30 are hard to find in some some places - but I managed to get my oil stained hands on a few quarts of 76 High Performance Full Synthetic TRACK Formula in 10W 30 (20W 50 also available). Got mine from Sparks Oil Co. in Reidsville, NC. $55/ case of 12 plus shipping.
The stuff is made in LA. GF-3 rated. SJ API
482F Flash Pt.
-58F Pour Pt.
10.4 cST@ 100C
3.3 High Temp/ High Shear Viscosity
1.1 Sulfated Ash
9.0 TBN
0.128 % Zinc
Mine was made in late 2003. Rumor has it that within Nascar, Richard Childress Racing, Hendricks Motor Sports and other engine builders have bought the same 10W 30.
Should be good for 500 miles in my truck - you think?