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The main concerns when starting a diesel engine in cold temperatures are oil viscosity and the stress on crankshaft bearings.  In the lifespan of a properly maintained engine, over 95% of the engine's bearing wear will be attributed to cranking and start-up.  This applies to both diesel and gasoline engines.  Any reduction in start-up stresses and loads will extend engine life and performance.  Your oil choice is a good place to begin.


In recent years, there have been several breakthroughs in oil development.  Since viscosity choices must match the climate, the latest crop of "winter" oils from major commercial oil producers is noteworthy.  I've been running 15W-40 Delo 400 year round in the '05 Dodge Ram Cummins 5.9L, and the engine uses negligible oil between changes.  (The most that's ever been consumed was 1/2-quart in a 5,000 mile change cycle that included towing an 8,000# trailer up I-8's long 6% grades from San Diego to Anza-Borrego and back.)  The engine does not leak, a major tribute to modern design seals at the crankshaft and timing cover.  Oil pressure has always been respectable and remains the same today as when the Ram 3500 left the dealership lot over 140K miles ago.  


I have recently considered changing to 5W-40 Delo 400 or equivalent diesel oil for winter protection.  Rotella, Ursa, Delvac and Delo are each excellent commercial/fleet products.  I would run this oil year round.  The 5W cold flow can dramatically reduce cranking stresses on start-up when the truck parks away from its block heater in the winter.  Delo in this viscosity is a synthetic base formulation, which does increase the cost.  Here's a link to Delo oil products.  Note that Texaco's "Ursa" label is also in the listed oil offerings:




Short drives with a diesel, in the winter especially, are torture.  My office is around two miles from the I-80 onramps.  In the winter, when below 45 degrees F, if I'm headed to Reno on a cold day, I can be three miles down the interstate before the engine reaches full operating temperature...and that's with the block heater plugged in the night before!  I rely on the additional 27 miles of interstate cruise to disperse the cold start/warm-up diesel fuel particulates in the crankcase. 


Note: We get plenty of sub-freezing weather in the winter, and I always use the factory block heater before a planned trip, allowing 12 hours or so of coolant warming before start-up.  I installed a block heater on the 4.0L Jeep Cherokee gasoline engine and use that heater every night in the winter, as this is our daily driver.  A block heater is a must for any diesel vehicle parked outside.  45 degrees F is my magic temperature for plugging-in the block heater before a run.  With a switch to 5W-40 oil, I might change the block heater plug-in to freezing temperatures—or maybe keep with the 45 degrees F practice.  The heater works nicely with the block warmed first!


I also use a battery maintenance device nightly in the winter.  On the Ram truck that parks for extended periods, the device remains connected continuously.  A Battery Tender or CTEK charger works fine for this purpose.  The CTEK has many additional features.  For more information on the CTEK charger, here is the link to my article and HD video on the CTEK:  http://www.4wdmechanix.com/CTEK-Battery-Chargers-for-Battery-Maintenance,-Restoration-and-Storage.html


Note: A Battery Tender has kept the OEM Mopar batteries in good condition since we purchased the Ram 3500 new, and that was 10 years ago!  I attribute this to the battery maintenance device, which stays on when the truck parks in the winter or even in the summer if the vehicle will set for some time.  The new CTEK charger has a Reconditioning de-sulfate function that I will try on these two batteries, disconnecting their cables first and isolating each battery.  10 years of service is remarkable life for diesel batteries!


These measures provide the least load on the engine at start-up and provide the best method for getting oil to critical bearing parts.  If your Dodge Ram Cummins parks in a cold climate, consider use of the block heater and battery maintenance device.  Select the right viscosity oil for your climate and driving demands. 



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