More insight regarding those new engine oils
Regarding the April Mechanic on Duty item on the new GM GF-5 oil or dexos1 oil, I am an Amsoil Synthetics Dealer and got the following information from their February 2011 Dealer News:
The new API SN, ILSAC GF-5 and dexos1TM specifications were introduced in the fall, mandating improved fuel economy, oil robustness and emissions system protection.
The dexos1 and GF-5 specifications are designed to address the unique demands presented by modern turbocharged engines and engines running on ethanol fuels (E85).
Because a number of GM engines with variable camshaft timing use motor oil as a hydraulic fluid, the dexos1 specification also requires an increased resistance to aeration. GF-5 oils cost about 15-20 percent more than GF-4 oils, while dexos1 oils carry an average 25-30 percent price premium.
The main objectives of the new specifications are to improve protection for modern vehicles and squeeze as much additional fuel economy as possible out of motor oil. AMSOIL OE and XL Synthetic Motor Oils are API SN and ILSAC GF-5 licensed, and OE 5W-30 (OEF) and XL 5W-30 (XLF) are recommended for applications requiring the dexos1 specification. The top-tier line of AMSOIL synthetic motor oils is being repackaged to reflect the latest industry specifications.
Jeff Hubbard Owner MotorSport Oil Sturtevant, Wisconsin