Did a little experiment today. I was in Fairbanks this week and today it was between -35* and -40*F. Quite frankly I was too lazy to park my truck behind the building and plug in, so I just left it running.

2015 F350 KR, 63k miles. Fully deleted and tuned with a PPE Ez-Lynk. I've been running the stock tune because mileage seems about the same between all of them and when it's winter with ice and snow, you don't go anywhere fast. 5W40 synthetic oil with 7300 miles on it and 220ish hours. Change engine oil soon light has been on for the last 200 miles and 20 hours.

I have the BD Diesel high idle kit with the rotating switch to adjust the idle level. Fuel consumption was monitored using the truck computer, which I have found to be very accurate on a consistent basis. Computer was reset at the start of each trial.

Trial 1: RPMS set at 1250 via high idle kit. Truck idled for 6 hours, 10 minutes. Fuel consumption was indicated at 5.2 gallons, or roughly .85 gallons per hour. Engine oil temp was about 185*F (remember ambient temp is -40). I was pretty surprised at how much fuel it used.

Trial 2: Back from lunch at Taco King. Figured the truck itself is pretty smart, so if the engine got too cold, it would probably boost the RPMS on it's own. Turned high idle off. Idled for 4 hours 15 minutes. Fuel consumption was 1.8 gallons, or roughly .43 gallons per hour. Engine oil temp was 150*F. Much more reasonable consumption.

.85 gallons an hour is pretty expensive but .43 gallons an hour is much, much more economical.

The biggest difference, besides fuel consumption, was engine oil temperature with a 35* difference. Is 150*F a safe, sustainable oil temperature for these engines to idle at without causing excessive wear?

 

I've noticed that when temperatures are single digits and below that the truck will idle up as well. I've also noticed that it seems like 150 is a target that it tries to maintain.

When you went out to the truck after the 4:15 hours how high was it idling?

 

You got off lucky 90Pioneer if all you had was -40F... NWS listed the official low for Fairbanks at -59F. I don't know if you know this, but the electronic temp gauge in the cluster won't register anything lower than -40F.

 

I'm surprised it doesn't register "Are U F&$@ing Kidding Me!!??" below -40

 

When I came back it was idling around 750-800 RPMS

 

I didn't know that. My temp gauge is in the sync screen in the dash. Will mine register -40? I thought I had seen -41 but can't say for sure.

I was all over Fairbanks this and don't believe it actually got to -59....that was read by an accurate temperature gauge anyway. Unless it just happened to be in a select pocket of extra cold air. But -59 certainly didn't seem to be wide spread in Fairbanks.

 

This made me spit my drink out!!

 

Something about electronic sensors not being accurate below that temp. Not that they can't display it...

Here is the article that said Fairbanks was -59F....

https://www.adn.com/alaska-news/weat...les-on-alaska/

59 below recorded in Interior as cold snap settles on Alaska

 

Ford equates 1 hour of idle time to 25 miles of service. So you are at least ((20 + 6.17 + 4.25) x 25) + 200 = 961.5 miles past due for an oil change, not counting the number of miles it takes to get to Taco King.

If the concern is how to minimize excessive wear, then change oil more often... at least keeping up with the recommended service interval. Ford considers your operation "Severe Service."

 

Best response!!!