Riflesmith,
I'm an Amsoil user, but this gives a good example of why I (and perhaps others) sometimes get frustrated with their marketing. When I go to their link, I find a 10W-40 oil that "looks" like it should be our very first choice. Four-ball wear (which some feel inappropriate, but that's another issue) that is competitive (out to the 3rd decimal place) with the 5W-30 oil Amsoil says is "best" for our application; volatility that is very close to the thicker 15W-40 (addresses those with blow-by bottle concerns), pour point that is lower than Delvac 1 5W-40, and a nice, thick -40 designator that soothes the nerves of those who tow heavy or just want a viscosity closer to what the owner's manual calls for. All the ratings for HD diesels appear to match the 15W-40 option, and a few are included that the "best" 5W-30 doesn't list, which makes me think the 15W-40 really is the better HD option, not the 5W-30 as the Amsoil tech line will tell you. So here's what rubs me - why is this oil not even listed under the Heavy Duty truck link with the other options? In other words, is there a catch, cost or otherwise?
I know you've always shot straight info on this board, so my frustration is not aimed at you in any way, it's more of a request to help me understand Amsoil's logic for listing other oils in both the "car" and "truck" categories, and listing this one only under "car" even when it carries so many diesel ratings. Or is it just that I expect too much out of their web page?
Now that I've gotten all that off my chest, do you have any personal opinions about the 10W-40? Have any customers or friends using it in their trucks?