5W-40 Winter Compatibility

Hey guys. So I live in one of the colder states where it routinely hits subzero temperatures in January/February with spikes below -20 F. I'm looking at AMSOIL's signature series 5W40 diesel oil, and is there any reason not to use this for my 6.5 L HMMWV in the winter?

My thoughts are that it would help with startups and feed oil to the engine faster while it gets up to operating temperature. However, maybe there's a reason outside of cost why the military doesn't list 5W40 in its recommendations. What's your opinion?

(Also, can anyone tell me the AMSOIL part number for an A2 HMMWV oil filter? Thanks)

The cost is a factor with the military They also use 15W40 in transmissions on big trucks to keep the supplies simple.
Personally I would just put a block heater on it and be done with it , because your going to want to dumb the 5W40 before temps warm up in the spring.

I looked it up in the manual for you, since it is frowned upon for me to tell you to do it...

above +15 F = OE/HDO 30
+40 to -15 F = OE/HDO 10
+40 to -65 F = OEA (oil, engine, arctic)

I use what the manuals tell me to.
You can look for the filter number for an H1.

as mentioned above, the block heater or pan heater may be helpful on those chilly nights.

A properly operating glow plug system is more important than the oil for starting in winter climates. Wide open throttle is a must also.I use 15/40 rotela and have no problems starting at below 0 temps. They (diesels) don't like it,but they will start.

diesel dave said:

A properly operating glow plug system is more important than the oil for starting in winter climates. Wide open throttle is a must also.I use 15/40 rotela and have no problems starting at below 0 temps. They (diesels) don't like it,but they will start.

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Let me weigh in here.

I spent over a decade in an area that went below -40 C/F [not a mistake, -40C=-40 F] regularly in the Winter. If you're really afraid of the cold, go with a full synthetic AND use a block heater, because most oil gels at -20F IIRC, and most synthetics gel at less than -35, making them superior. Gelled oil will prevent you from cranking over, and will allow you to score your engine. I never had issues with my Landcruiser Toyotal 2b Diesel but I had synthetic fluids everywhere, block heater, tranny heater for a manual tranny, front and rear pumpkin heaters, and a fuel tank heater and anti-gel in the Diesel fuel with fuel line heaters and insulation.

I don't know how cold it gets in Wisconsin, so you need to make your choice based on conditions you face in your neck of the woods.

Diesel Dave, in general I would agree but...Glow pugs are important for starting UNLESS YOUR OIL IS GELLED.

BMW runs full synthetics up North and deleted most block heaters as full synthetic kept the oil from gelling.

Make sure your batteries are good as you will lose > 50% cranking amps at -40C/F.

My humble advice.

T

I live in close proximity to the arctic circle all my diesels even the 6.2 get 5w40 synthetic it will cover you from -30 to 80 above

I was commenting on the OP's Wisconsin location. NOT arctic conditions.