I have been using Delo 400 motor oil in my 5.9 l Cummings Diesel. I would like to switch to a synthetic oil. Anybody have a recommendation? What about a blend? Also, how long will I be able to go between oil changes?
Why switch? My concern would be that the regular oil has been used for a lot of time. Folks that switch to a full synthetic find they experience seal leaks as the seal material gets conditioned to the regular, thicker, dino oil.
Not much better results with a blend, either.
Given the fact that it's a diesel, I don't think you'd want to lengthen the oil change service interval too much.
The only real cost benefit to synthetic or synthetic blends is the extended oil service interval and I would not recommend that with a diesel.
My thought here is that you can save yourself some money by sticking to conventional oils and your regular service interval.
What year is your truck? If it's pre '07 when the final legislation went through to only use Ultra Low Sulphur Diesel, then an oil with a higher lubricating factor would be required as older diesels got some of their lubricity and better cetane from the sulphur in the Low Sulphur Diesel (~500ppm) fuel. If you want to switch to synthetic, I'm a fan of amsoil myself, and their series 3000 is designed for pre-'07s. If it's '07+ then you can use their premium syntheic 5W-40.
My truck is a 2004 with the 5.9l Cummings. The reason for changing to synthetic is that I am driving to Mexico R/T about 6000 miles. On regular oil I would have to change there, which costs me 100 bucks. I would like to be able to make the R/T without oil change.