10w30 vs 15w40 son

I'm pretty sure Freightliner said 10 30 is ok for dd15s. I think past 13 or 2015. It's recommended now, for 18 on...?? I asked like 2 years ago, so it's fuzzy. We are going into mid spring. I think the 30 weight is better for fall to mid spring, not summer. Just call your dealership???

 

I do the same. I own my truck. If I push off a rebuild by 100k. By changing the oil every 15k miles vs 50k I'm way ahead of the game. In stress alone.

 

Interesting. It never occurred to me that an oil type might affect mpg. 10-40 vs 15-40. But to what extent? I've used mostly Rottella 15-40 every 15 000 miles, if not Rottlella then Delvac. At about 10K, it is time to add 1 gal, to go back to the MAX mark on the stick, and it lasts another 4-5K miles before I change it.
I am almost at 1370 000 miles on Cummins ISX, so the routine and oil type must have been right but I think I agree that once the oil starts burning it is done. So, I may shorten the intervals to 10-12K. I have never done oil samples either. Whenever I changed oil at a less known repair shop with "whatever 15-40" barrel oil, it started burning after 5-7 K miles. So I prefer to change it at Speedco, Sapp Bros, etc, so I know that I have the oil quality, not some fake. I wish I could change it myself from the bottles, but I have no good place to do it.

P.S.
Summertime, I don't mind mixing in 1 gal of Lucas oil additive. It nicely boosts the oil pressure.

 

I run 10-30 because it’s what the book says. Last truck I changed filters at 20k and oil and filters at 40k because I was running heavy and was borderline severe service according to the book. Had 600k on it when I sold it and never used a drop of oil between services. This new truck I’m going to let ride until 70-75k because the book says I can.

 

10-30 in the new truck. I’ve always ran 15-40 before. But the new truck calls for 10-30 so that’s what I run. I also am running delvac. If it’s good enough for the factory fill I reckon it’s good enough for the rest of the time. I was always a rotella fan ever since they put out them cassette tapes in the early 90’s. Nothing like some free trucking tunes for buying a jug of oil.

 

15/40 Rotella with a gallon of Lucas.

 

Back in the normal aspirated days Cummins used to recommend either straight 30 or 10w30. When turbos came into use is when 15w40 was developed and that became standard issue. The heavier oil was needed for the extra heat and pressures caused by the turbos. 30 wt with turbos used to mean more oil consumption and less miles between overhauls. Same with the two stroke Detroit. They used straight 30 until turbos and then went to straight 40.
Now they are going thinner again for the government regs of fuel mileage not so much the longevity.

 

I agree with you when the oil starts burning it's done. Both trucks are usually ready for a gallon around 18k, so anywhere 15-18k they get changed. Regular 15-40.

 

I briefly switched to 10w30 in my 2013 isx last year but while having some unrelated work done by Cummins in omaha I told them of my switch .
They definitely did not approve and almost banished me to Cummins hell.

 

Boss switched his fleet over to 10/30 around 5 years ago . Mostly cats and series 60 reason was mechanics or drivers kept putting 15/40 in the new trucks which are too tight for 15/40 apparently.. drivers found it started easier when using bunk heaters overnight but engines drip a bit more and use a bit more oil .. fuel mileage was a wash or so minor that it’s not noticeable. My observation is 10 to 12 less psi on gauge . No observable temp rise on oil pulling the 8 to 10 % grades it seemed to the same as the 15/40 oil . 2 buddies who work elsewhere had their fleets switch all trucks to 10/30 with no real issues because they service their own trucks as well and it’s easier to have one oil . Within 10 years 15/40 will be like 24.5 tires a bit harder to find in quantity.

 

Something to ponder

Oil pressure is only half the equation. There's still flow to consider. You can have all the oil pressure in the world but if the oil isn't flowing easily enough to provide fresh, cool oil and remove heat, its kind of a wash IMO.