Amsoil continually upgrades their standard formulations. One of the main things they have been doing is reducing the high temp evaporation, ie Noack volatility, of all their oils. The Noacks of the 5w-30/10w-30 have been reduced from approx 7.0% to 4.9%/5.5% respectively. Noack of the 15w-40 has been reduced from 6.7% to 6.2%. This extremely low volatility helps keep the oil from excessive thickening over long drain intervals and reduces oil consumption and exhaust emissions.
I've also noticed that the detergent/dispersant mix in the ACEA , A3/B4 rated, 0w-30/10w-30 has changed.
Old formulation:
Mg, 300 ppm
Ca, 3000 ppm
New Formulation:
Mg, 700 ppm
Ca, 2500 ppm
This change is just starting to show up in UOA's, so it was probably made 6-8 months back. I monitor the spec sheets Amsoil puts out pretty closely and there is ususally a formulation upgrade about once every year to 18 months.
TooSlick
Dixie Synthetics
[ June 01, 2003, 09:12 AM: Message edited by: TooSlick ]