2008 Dodge 3500 Cummins oil weight

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We are looking at another very cold winter here in Northern Ohio and I am worried about running a 15w40 in my Dodge Cummins...I have read that Cummins is adamant that a 15w40 be used and it has me wondering if I could get away with a 10w30 for the winter months...or are there any other suggestions for a diesel rated oil that would help this engine in colder weather...I cannot always plug it in and sometimes have to do cold starts.
 
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Shell Rotella T6 5w40 would be a much better winter oil for your Dodge diesel. It carries all the modern diesel api specs too. Starts great in cold weather and is superior to most 10w30 diesel oils imo. Also it's available at most Walmarts in the jug making it a huge value.
 
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Originally Posted By: oliver88
or are there any other suggestions for a diesel rated oil that would help this engine in colder weather
5w-40 is approved by Dodge for usage in this application.
 

dnewton3

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Do you "need" to change grade, or just "want" to? 1) what proof do you have that the current lube you are using (and presumably used last winter) did a poor job? Do you have UOAs and PCs to show the lube failed to protect in some manner? 2) what manner of measurement would indicate an success in this circumstance? What is your measuring stick that will be used to judge a meritorious approval? While not common, there are examplese of 10w-30 dino HDEO doing quite well in today's modern diesel engines. The thinner grade will assist in a bit quicker flow, and proabaly a bit easier starting. But don't expect miracles overall. There won't be a big shift in performance or wear. The noise of typical operation in terms of wear is greater than what you'd be able to prove in singular season observations. I see no "need" for T6, unless you intend to greatly increase your OCI to some very long factor. There is a difference between feeling and knowning. Unless you have quantifiable performance parameters that you'll use as a baseline, then you'll never be aware of any improvement, or lack thereof. Once you establish the baseline, then what measurables would indicate to you that success has been achieved? Don't look at inputs; quit looking at the VOAs. Most any lube is "good enough" for what you're to put it through. Rather, look at UOAs and other tangible criteria; what indicators show a failure of 15w-40 where 10w-30 0r 5w-40 would usurp it?
 
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My '06 Cummins in my sig isn't happy starting unplugged in winter with 15W40 either, check your local AutoZones for clearance M1 TDT, I picked up 3 oil changes worth a while back for $1/quart. 10W30 would work fine too.
 
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No diesel is really happy starting unplugged when it gets down to -30 at night. As long as cranking speed is high enough it really comes down to how well your starting assistance (glow plugs or grid heater) and injectors work when they are that cold. IMO the cummins is at a slight disadvantage here in that it doesn't have glow plugs and relies on a grid heater only which does work well if it can sufficiently heat the intake air. Thinner oil will help with initial lubrication as it will circulate through the system quicker but I don't know how much it really helps with cranking speed and cold starting ability. At least I couldn't perceive a noticeable change between 15w-40 and 10w-30. Your batteries and starter are going to be a much bigger help as well as just having a warm engine from being plugged in.
 

oliver88

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No real data just know that it was sometimes sounding pretty rough when it started at -15 F with the 15w40 in it. I run Rotella 10w30 in all of our diesel tractors in the winter, helps tremendously with cold starts. Starter and batteries are all in top condition.
 
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If you find yourself across the border, there's a Canadian product called Delvac Elite 222 0w-30 that I'm sure would provide the cold weather performance you're looking for.
 

dnewton3

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Originally Posted By: oliver88
No real data just know that it was sometimes sounding pretty rough when it started at -15 F with the 15w40 in it. I run Rotella 10w30 in all of our diesel tractors in the winter, helps tremendously with cold starts. Starter and batteries are all in top condition.
You're obviously already aware of the benefits of using a thinner lube in winter. I recommend running the 10w-30 Rotella. You already have it, and it works well. After 5k miles, run a UOA just to convince youreself of what you probably already suspct; it will be fine. You can then compare/contrast that UOA data to macro data. Presuming everything is OK with your engine (no leaking injectors, no intake leak, etc), I would be genuinely surprised if the 10w-30 data was anything but "normal".
 
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Originally Posted By: ironman_gq
No diesel is really happy starting unplugged when it gets down to -30 at night. As long as cranking speed is high enough it really comes down to how well your starting assistance (glow plugs or grid heater) and injectors work when they are that cold. IMO the cummins is at a slight disadvantage here in that it doesn't have glow plugs and relies on a grid heater only which does work well if it can sufficiently heat the intake air. Thinner oil will help with initial lubrication as it will circulate through the system quicker but I don't know how much it really helps with cranking speed and cold starting ability. At least I couldn't perceive a noticeable change between 15w-40 and 10w-30. Your batteries and starter are going to be a much bigger help as well as just having a warm engine from being plugged in.
I own both grid heater and GP systems and I would take grid heaters over glow plugs any day. They will last the life of the engine 99% of the time where Glow Plugs are much more prone to failure and once you lose one or two it makes starting in cold weather more difficult. A glow plug system has a much higher maintenance/replacement cost compared to a grid heater. I've never had a problem starting mine in -20F weather unplugged. I've also witnessed my brother in laws truck start after sitting at the family cabin in Wyoming at 9k feet in sub zero weather for days on end with zero problems. The only disadvantage I can think of is they take slightly longer to heat up compared to modern GP systems, but I'll take that trade for the reliability any day. To the OP, I live on the shore of Lake Erie where we saw the coldest winter in 30 years. Lots of sub zero nights, 15w40 (synthetic) is all I've ever ran. My brother in law I mentioned above has always ran the same in a much colder climate and has never had any issues in the 10 years and 320k+ miles he has owned his truck. Even the 2014 Cummins engines STILL recommends 40w oil, so I see no reason to use anything else. Rest assured they know their stuff.
 
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The Cummins holds about 11 liters of oil that is slow to warm up along with the engine. At what point into the daily duty cycle would a 15W40 out perform a 10W30 engine oil? At 30 miles? After one hour of operation? Maybe more? I would guess that if the oil is not fuel diluted and in good physical condition, maybe never. The same logic would apply to gasoline engines that have a large sump capacity. At which point in the daily life of those engines would a 5W30 provide better lubrication than a 5W20 engine oil? Maybe never as well? I think that the entire engine oil viscosity issue has to do with the point in the daily life cycle of a non commercial where a higher viscosity engine oil becomes the better choice. The preponderance of engine oil temperature should dictate the desired grade for long engine life. Typically too many "what if's?" come into the discussion.
 
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The Cummins engine has an oil heat exchanger that has engine coolant flowing through it. So the oil is heated by the coolant as the engine warms up. This greatly speeds warmup of the oil. The heat exchanger then cools the oil if the engine is working hard enough to get the oil hotter than the coolant.
 
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Originally Posted By: A_Harman
The Cummins engine has an oil heat exchanger that has engine coolant flowing through it. So the oil is heated by the coolant as the engine warms up. This greatly speeds warmup of the oil. The heat exchanger then cools the oil if the engine is working hard enough to get the oil hotter than the coolant.
This is the same way as our GM 3500 vans. Trans and crankcase fluids are heated first and then cooled later in an operating cycle as they are exposed to the coolant. This would seem to be a great strategy for the guys in the frozen North...
 
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