15-40 isn't just for diesel. It is a good oil all around. But it all comes down to brand specifics.. There's 30 and 30 HD. HD usually is in relation to diesel engines, unfortunately with all of the new emissions not only for gasoline engines, diesel as well, oils are slowly fading out the heavy zinc content due to it will cause catalytic systems to fail. I can go on forever on the emissions side of it.. For diesel systems.. I deal and work on them daily. I hate working on gas motors...
I run shell 30 wt with zinc additive. No issues... I would always stick with what your OEM recommends.. Especially if warranties are in place...
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