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Cummins ISL Oil recommendation

Mile_High
Explorer
Explorer
Getting ready for my first service, and I see the shop offers standard oil, semi synthetic, or full synthetic. Terrific 🙂

Any idea what would be the best oil for the ISL that operates as a vacationer with periods of storage >120 days and may operate in weather >120 F or <0 F?

Previously my Ford diesels were always serviced by Ford and I never paid attention to what they put in as they were always still under warranty.
2013 Winnebago Itasca Meridian 42E
2013 Jeep Wrangler Unlimited Sahara Towed
24 REPLIES 24

SPRING_STREET
Explorer
Explorer
Have always used Rotella 15-40. Never tried any others!
2011 MOUNTAIN AIRE 4344, FMCA F334596, Cummins Power Play,Good Sams and KOA member..TOAD 2017 Ford Edge Titanium with a 6 cylinder Engine, License plate "TOWED" > RoadMaster Night Hawk Tow Bar and Base Plates. 😉

sjholt
Explorer
Explorer
Delo LE 15-40W is the best oil for your Cummins. It has all the good additives including moly that other diesel oils do not have. In all my oil analysis it held up the best.
Skip
1996 32' Monaco Windsor DP
Cummins 5.9L 230+ HP
5 Airbags in front- 4 in back

azdryheat
Explorer
Explorer
Seems to me you can't go wrong with any Diesel oil, just how much do you want to spend.
2013 Chevy 3500HD CC dually
2014 Voltage 3600 toy hauler
2019 RZR 1000XP TRE

chuckftboy
Explorer
Explorer
My motor gets Valvoline Blue. If its good enough for the Cummins factory to use, its good enough for me. I change my own oil so its cheap enough to go with the good stuff.
2019 Horizon 42Q Maxum Chassis w/tag
Cummins L-9 450 HP / Allison 3000
2006 Jeep TJ and 2011 Chevy Traverse Tows

Mile_High
Explorer
Explorer
It looks Like Speedco offers Rotella T and Baldwin Filters for $299, so is that Rotella T1 most likely as the standard oil?
2013 Winnebago Itasca Meridian 42E
2013 Jeep Wrangler Unlimited Sahara Towed

steveownby
Explorer
Explorer
wolfe10 wrote:
Many reasonable choices.

Shell Rotella T 15-40 and Delo 400 15-40 are popular choices and are available at Walmarts, etc.

You will not wear out that engine in an RV, so worrying about whether a special (read that expensive) oil extends engine life from 800,000 miles to 1 million miles is not really relevant.

If you have some special circumstance such as pulling a 10,000 pound trailer through the mountains in the summer, that may warrant other considerations.


Brett, is, of course, correct. The spec too look for is CJ4 and the two called out meet that spec.
Steve Ownby
2003 Monaco Signature

Full-time since 2007

Ivylog
Explorer III
Explorer III
20 years ago I researched this at a shop that rebuilt million mile truck engines. They said that engines using Dell 400 were amazingly clean and those using Shell Rotello T had a slight amount of buildup. Since I often let my heavy equipment sit for extended periods I went with Shell R T in the hopes the buildup would help protect the engine from corrosion.

No way would I pay for synthetic if I changed the oil every year which I do not and I only use Shell RT which I change every 15,000 miles.
This post is my opinion (free advice). It is not intended to influence anyone's judgment nor do I advocate anyone do what I propose.
Sold 04 Dynasty to our son after 14 great years.
Upgraded with a 08 HR Navigator 45’...

crasster
Explorer II
Explorer II
I love Supertech oil and they do sell Diesel oil. They are packaged either by mobil or shell. I've never had a problem using it and would suggest it to anybody. Much cheaper at walmart.
4 whopping cylinders on Toyota RV's. Talk about great getting good MPG. Also I have a very light foot on the pedal. I followed some MPG advice on Livingpress.com and I now get 22 MPG! Not bad for a home on wheels.

wolfe10
Explorer
Explorer
Many reasonable choices.

Shell Rotella T 15-40 and Delo 400 15-40 are popular choices and are available at Walmarts, etc.

You will not wear out that engine in an RV, so worrying about whether a special (read that expensive) oil extends engine life from 800,000 miles to 1 million miles is not really relevant.

If you have some special circumstance such as pulling a 10,000 pound trailer through the mountains in the summer, that may warrant other considerations.
Brett Wolfe
Ex: 2003 Alpine 38'FDDS
Ex: 1997 Safari 35'
Ex: 1993 Foretravel U240

Diesel RV Club:http://www.dieselrvclub.org/

Two_Jayhawks
Explorer
Explorer
Valvoline Premium Diesel oil is what Cummins recomends for my ISL.
Bill & Kelli
2015 DSDP 4366 pulling a 21 JL Unlimited Sport
2002 Safari Zanzibar 3906 gone
1995 Fleetwood Bounder 36JD gone