Answered Oil question...15w40 vs 10-w30

[GlampDaddy]

I just took my coach to Freightliner Austin for an oil change and lube. The invoice says they used a 10w30 synthetic oil instead of the Cummins recommended 15w40. Their service manager is willing to correct the mistake, but feels strongly that the 10w30 is fine. My inclination is to stick with what Cummins says, and I am waiting on a return call from Cummins Support to hear their version. We're headed for the Badlands, Montana, etc in two weeks. What says this group?

 

[Neal]

Interesting you checked and determined the difference, I have no idea what the oil is supposed to be as I just trust Gaffney or whomever, in fact my oil was last changed in Tucson when the head gasket was replaced and I don't know what they used. I checked the invoice and it doesn't state it. If you know what it's supposed to be and they're willing to change it then I'd save let them correct it. Maybe call Gaffney and ask them?

 

[TJ&LadyDi]

IME, the 15W40 and 10W30 are fairly comparable, except in extreme heat or cold. When temps are really low, the engine will turn over a little easier with 10W30 and in really hot conditions, 15W40 provides a little better lubrication.

I would go with whatever Cummins Support says when they get back to you.

TJ

 

[GlampDaddy]

Thanks for the input! I heard back from Cummins Support, and they say all is well in my world. 10w30 is an acceptable standard and will do no harm. Now, once I install that dash switch for my stereo...

 

[Joe Hogan]

Interesting topic. As long as the oil is spec'd for a diesel engine, it does not appear, per discussion boards, to be that much difference. When I drove diesel autos I always used 5w40 as spec'd by the mfg. Never thought to use any other weight. This was operating in Minnesota, Iowa, Connecticut, Vermont, Georgia. Over three vehicles, around 450-500k miles, never an issue.
One of my oil information sources is the discussions on Bobistheoilguy. Using 10W-30 over 15W-40 & 5W-40

 

[Webz]

Let me show how anal I am. When I bought my coach it was new. I do most maintenance including oil changes. I contacted Gaffney and asked what oil came in the engine from the factory. Gaffney said Rotella 15W40. I thanked them and got to thinking. Gaffney did not make or build the engine. I contacted Cummins and asked the same question. Cummins said they put Valvoline Blue. I bought the Valvoline and changed the oil. Sent a sample to Blackstone Labs. Told the lab I did not know what kind of oil I had in the engine but it was Rotella or Valvoline. Blackstone said I had Valvoline since my sample had titanium and Rotella does not. I know both meet specs for the engine.
It is not the first time Gaffney has mislead me.
Like most things in an RV, go to the manufacturer of the item for best info.

 

[Old-RV'er]

As stated the 10w-30 works better in colder climates. The 15W-40 works better in hotter weather. The big deal is, did they use the correct specification type of oil. I use delo 15w-40 specifically rated for Diesel Engines. The place I worked for 28 years used it in all our big rigs, and man lifts, etc. if they were diesel. I used in for those same periods in all my pickups and such. The weight difference is not as important as the oil specification. I would be more concerned with that. IF you are driving through excessively hot, mountainous terrain take it easy going up and watch the engine temps. Especially let the engine cool down after pulling off or in for the evening. Follow Cummins warm-up/cool-down requirements.