They come with 10w30 from factory, but once that’s dumped 15w40 goes back in. I know several owners of fuel transportation business, and grease removal business. The fuel transportation owner has 55 gallon drums of Delvac 15w40. He owns kenworth and Volvo tractors. The Volvo comes factory fill with rotella 10w30, kenworth comes factory fill with Delo 10w30. He resolves oil 15,000 miles with all Delvac 15w40 in both branded tractors. Talk to any over the road trucker and he will tell you they don’t run 10w30, they use 15w40