I will second the question as to which gas engines can beneft..
It all depends on what grade the engine needs. If it can take an Xw40, then no problem- HDEOs are commonly available in 5w40 and 15w40 weights.
If it calls for a 5w30 or 5w20- no such luck, although Rotella conventional comes in 10w30 which could be used in place of a 5w30 in warmer climates.
Some engines that are technically spec'd to take an Xw30 have been shown to perform very, very well on Xw40, too- the Jeep 4.0 comes to mind.