Synthetic vs Dino Oil ??

If your Cummins ISC has only 30,000 miles, chances are it's only seen one oil change. Maybe two at best. Cummins oil change interval (mileage wise) is 15,000 miles, or annually. That's according to my 350 ISC owners guide.

I for one have always been a synthetic oil guy for all of my vehicles. However, when I bought my DP, I called Cummins with regard to some technical information about the engine. One of the questions was about the engine oil. They told me the it was certainly fine to use synthetic oil if I chose to do so and wanted the added expense, although it wasn't really necessary with the amount of my usage (currently at about 8,000 to 10,000 miles per year max.)So, I've been using Valvoline Premium Blue (Dino, not synthetic) as recommended in the engine owners guide. I do my own oil and filter changes.

One other thing that I may as well mention...Upon my previous oil change, I installed one of those Oil Change Valves (used to be known as a Fumoto Valve). Well, the oil change this time was much neater and without any mess as I was able to drain back into the individual jugs from the previous oil change BUT, IT TOOK FOREVER TO DRAIN 20+ QUARTS OF OIL OUT OF THE OIL PAN WITH THAT SILLY LITTLE VALVE! If I recall correctly, it took about a half hour to almost 45 minutes to drain the oil! :S

Another "brilliant" idea of mine that semi-backfired!

One of the great myths of Synthetic oil is "You can't go back".

What the *(@#*$ do you think blended oils like DuraBlend, Max Life ,and so on are? Mixes of synthetic and dino.. You can switch back and forth.

That said. I'd stick with either full synthetic or a blended oil at least.. I run Blended in both my car and MH (Car by request, Motor home because the shop that does my oil changes by default uses blended, I'd use full in it if they had it but the difference is not that great so as to go out and buy my own).

Oh, the kernel of truth in the myth.
ONE early Synthetic, no longer made, did cause switch back issues.. But that was many years before the end of the last century.

Cummins gives no extended intervals for synthetic. There are some fuel mileage benefits but I doubt you can cover the cost difference between syn and dino. The synthetic has benefits at the temperature extremes, very cold or very hot. I use Delvac1300 15W40, Delo and Rotella 15W40 are other choices. Pick one. Change it yearly or at 15k miles. Get a used oil anaylis to track trends. Enjoy the trip!

No problems switching back to Dino. Unless you are doing oil testing and extended intervals on changes, or need synthetic for cold weather, then you are probably wasting money using synthetic.