10w30 vs 15w40 son

Is there any way to assess or measure the oil flow?

 

I run 5-40 mobile 1 full synthetic.

I've always run full synthetic.

I change the oil less, and with a bypass filter from the factory, you can go a #### long time between changes.

 

10w30 Mobil in the bulk tank goes in everything that is common rail injection.

Everything older gets 15w40 out of a drum. All CAT, N14 and anything mechanical. Which is not very often anymore.

 

Cat dealer we only had 0W-40 on the reel. You wanted anything else it came out of a bucket.

 

I’ve been on the X15 10w30 since I got mine from new. They recommend 10w30 but I swear everyone and their mom says they still only use 15w40 regardless of what it came factory filled it or recommended. I’m lost myself at this point. Is there even a benefit for switching between the two weights if my highs are 80-90 degrees and maybe as low as 20?!

 

Here’s what I read and the reason I stopped using 10-30.
Supposedly 10-30 is better for fuel mileage (you’ll never actually notice a measurable difference) 15-40 is better for the life of the engine.

After 300k using 10-30 in my Cummins I am running 15-40 now.

Old thread but still a good subject

 

I think at 200k I’m going to do just that. I pull hills all the time, motor is near 240 degrees, at 105k gross multiple times a day around this time a year. I for a few intervals switched to schaeffers to try to better the 10w30 path, but my mechanic kept nagging me that he hated the way the oil looked and felt when he’d drain it. Kept saying it smelt burnt and looked thin as hell.

What year and model is your motor?

 

2023 Cummins isx 565 hp. Already got 340k on the meter.

Was using Mobile Delvac 10-30 full synthetic but the Mobile 15-45 I switched to is a blend if I remember correctly.

I get the oil at my local Walmart and the 15-45 is a heck of a lot cheaper. I also get all my filters from TA in Vero Beach, Florida. Surprisingly they are the cheapest I can get from anywhere.

 

2017 579 with a 510 Paccar had 10/30 in it at least until I sold it Jan 2022 with 600k on it. Truck is still on the road hauling milk daily but I have no idea what they’ve done since.

2022 579 with a 510 Paccar had 390k on it when I sold it in April. Had 10/30 in it while I owned it.

In a 2026 589 now with a 510 Paccar and this company runs 10/30 in everything that calls for it.

If you’re concerned about the state of your used oil I’d probably send off a sample instead of what someone says it smells and feels like.