Cummins QSB oil viscosity recommendations

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jrmason

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Looking at the engine operators manual of a QSB 6.7 I operate, and they list 10w30 at a lower ambient operating temperature than 5w40. Can anybody elaborate on this? Does 10w30 really have a better CCS than 5w40? Seems backward to me but there has to be some reasoning here. I trust anything that Cummins publishes, just trying to understand the reasoning. Also, what are they trying to differentiate between "All Season" and "winter conditions" RE the 10w30? They are both multi grade oils, so? Reason for my questions, I'm considering switching to a 10w30 in my 14 Ram. 15w40 is sufficient most of the time but we do get to zero and below periodically a few months out of the year. I'm thinking a conventional 10w30 would suit me well based on the included picture, even though it is not recommended in my Ram owners manual. Thanks guys.

IMG_20181117_102210884.jpg
 
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@ George, they are the same engine, and being they are both tier IV compliant they both utilize the CM2350 (ECM). If you were to download the ISB owners manual it would be the exact same one. I'm aware of the cold weather advantages 5w40 carries,. I am specifically interested in why Cummins recommends 10w30 To a colder ambient temp. If anyone has some insight it would be appreciated. Thank you.
 
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For the ISB / B6.7, the recent switch to 10W30 for OEM FF is about fuel economy and nothing more. Off-road/non-vehicle applications generally would be assumed to have fewer cold starts and lengthier runs.
 
I've yet to see a 6.7 of any variation factory filled with 10w30. The book I took the picture from recommends 15w40 in ambient temps above 5*F, and lists the chart as acceptable alternative viscosities for temps below 5*F.
 
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To be honest, I really can't understand what they're getting at. I've seen the reverse, where some charts recommend 5w-30 only up to a certain temperature, and then 10w-30 for higher temperatures, particularly years ago, with the OEM perhaps not having the faith in the VIIs or base stocks of the 5w-30 in very high temperatures. The reverse, I don't get it. A 5w-40 is certainly not equivalent to 15w-40 in winter conditions, nor inferior to a 10w-30. Unless the authors can come up with a valid reason (and not something based upon old wives' tales or misconceptions), I'd call it an error.
 
Originally Posted by Garak
To be honest, I really can't understand what they're getting at. I've seen the reverse, where some charts recommend 5w-30 only up to a certain temperature, and then 10w-30 for higher temperatures, particularly years ago, with the OEM perhaps not having the faith in the VIIs or base stocks of the 5w-30 in very high temperatures. The reverse, I don't get it. A 5w-40 is certainly not equivalent to 15w-40 in winter conditions, nor inferior to a 10w-30. Unless the authors can come up with a valid reason (and not something based upon old wives' tales or misconceptions), I'd call it an error.
So would the OP be ok running a 10w30 HDEO? THank You in advance Garak wink
 
When it comes to winter starts, below 0F, 5W40 synthetic IS BETTER than 10W30 dino-in the old company '04 E-350 6.0 PSD, it was at the dealership in winter to get something minor straightened out and they took it upon themselves to change the (not due) Valvoline Premium Blue Extreme 5W40 full syn out and put in Motorcraft 10W30 diesel oil, then the van sat outside overnight for a nice cold soak. When I went to pick it up the next morning it chugged like an idling Briggs & Stratton, and fogged the whole neighborhood with unburned diesel. I have never used the AME Amsoil 10W30/30, it's probably better stuff, but YMMV.
 
Originally Posted by bullwinkle
When it comes to winter starts, below 0F, 5W40 synthetic IS BETTER than 10W30 dino-in the old company '04 E-350 6.0 PSD, it was at the dealership in winter to get something minor straightened out and they took it upon themselves to change the (not due) Valvoline Premium Blue Extreme 5W40 full syn out and put in Motorcraft 10W30 diesel oil, then the van sat outside overnight for a nice cold soak. When I went to pick it up the next morning it chugged like an idling Briggs & Stratton, and fogged the whole neighborhood with unburned diesel. I have never used the AME Amsoil 10W30/30, it's probably better stuff, but YMMV.
I have no doubts a synthetic 5wxx provides better cold start protection than a conventional 10wxx. Some interesting points I've found since coming across the picture I posted. FYI I previously ran Schaeffer's 15w40 in my 98 and continued to use it until I ran out, and have ran Mobil Delvac 1300 the last two intervals in my 14. Mobil Delvac 1300 15w40 CCS 6600 @ -20C, mPa limit of 7000 @ -20*C Mobil Delvac 1300 10w30 CCS 6600 @ -25*C, mPa limit [email protected] -25*C Mobil Delvac 5w40 CCS 6510 @ -30*C, mPa limit 6600 @ -30*C This is where things get a little interesting, at least for me as I have not studied cold weather performance of oils very closely. Mobil Delvac Extreme 15w40 CCS 6100 @ -20*C Mobil Delvac Extreme 10w30 CCS 6600 @ -25*C Schaeffer's 15w40 CCS [email protected] -20*C Interesting that there is no difference between the 1300 and Extreme 10w30. I threw in the Schaeffer's because that is what I have historically used, with a bypass filter on extended service intervals on my previous truck a 98. Being I "upgraded" to an engine with EGR and the occasional post injection event during Regen I decided I'd be better off sticking with the recommended intervals. This makes using Schaeffer's (or any synthetic IMO) less economical. However, looking at some of the cold weather properties has me rethinking the use of my all time favorite oil. The Schaeffer's also has a lower pour point compared to Mobil Delvac 5w40, (astm d 97) Mobil Delvac 5w40 -30*C Schaeffer's 15w40 -39*C I am beginning to think I would be better positioned to stop being a cheap skate and just go back to my Schaeffer's. We see weather frequently in the low teens to single digits with zero and below only averaging a handful of times a year. I never had issues with my 98 using this oil, and have many UOA's to be comfortable making the switch back. I suppose the old adage holds true here, if it ain't broke....
 
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No problem at all, jrmason.
Originally Posted by 53' Stude
So would the OP be ok running a 10w30 HDEO? THank You in advance Garak wink
I would say so. A 10w-30 is certainly a suitable winter (or even year round) choice. Up here, 10w-30 was the historical winter fill for diesels for an extended period, considering some of the 5w-XX and 0w-XX options weren't available, and are still mentioned in manuals, as we see. That manual does have odd wording and an odd chart, listing 10w-30 in two separate sections, looking at the second and third bar. There certainly are other options available, including 5w-40, 0w-40, 5w-30, and even 0w-30. If it were me, I'd have no problem running an approved 10w-30 year round, and the authors of the manual would seem to agree, despite their inelegant way of wording it or showing on the graph. They clearly have confidence with it in the summer. There certainly are Cummins approved 5w-40 and 5w-30 options, including the lube in my signature.
 
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