Dunno, can't say that I have a diesel personally.
My XV535 turns up to 9,500 rpm before the tach hits the little red line and my recammed Savage regularly goes over 7,000 rpm so yes I do invest in that little extra protection that is offered by synthetic oils as I deem it prudent.
I think I need it ....
Standard Savage engines never really see 5,000 rpm as the stock cam flat lines you about then and the highest temperatures we saw on Verslagen's test data shows that standard dino oils such as white jug Rotella would be good enough for normal Savage interstate temperatures and rpms. Hey, as a matter of fact stock Savage engines do run in the same rpm range as open road diesel engines -- ain't that a hoot.
However, the diesel engines are much more stressful engines than gasoline engines anyway, the Savage engine runs a compression ratio of 10:1 while diesel engines start with compressions of 20:1 and go up as high as 25:1 in some versions. The bearing loads in a diesel engine are quite extreme compared to anything gasoline driven.
Top fuel engines are closer in oil performance demands to diesel engines than our Savages are, so you are buying an oil that is performance overkill for the Savage when you plunk down $2.99 a quart at Walmart for that big white gallon jug of Rotella T .....
$2.99 a quart with known good for a Savage performance -- JASO MA rated and approved for motorcycle use.
Ahhhhh ....
Earl, can you hear me buddy?