One of the leaders in this field is GM, which is filling the engines of all its 2011 models with a new oil formulation known in the industry as GF-5 or SN grade. GM calls it dexos1.
The special grade is only given to oils that are designed to help engines run more efficiently and offer greater protection from wear. This latter element is increasingly becoming more important as vehicles switch to downsized engines that tend to extract more horsepower with the use of heat-producing forced induction mechanisms such as turbochargers and superchargers.
As for fuel economy using the new oil, gains are made due to less internal friction in the engine but the added cost--often between 20 and 25 percent more than regular oils--may negate any savings from the gains in fuel economy.
A secondary benefit to the improved fuel economy, however, is a longer lifespan for the oil, which equates to a longer time between service intervals.
Importantly, most automakers warn that using an incorrect oil for your vehicle may void its powertrain warranty so check your owner’s manual before your next oil change.
[Automotive News, sub req’d]