I have a 2016 F350KR (3.55) and have had it since new. It now has 53k miles.

So far when driving I am getting 13-13.5/mpg in the city, 14.5-15mph on highway, 12.5-13/mpg with the lance truck camper, and less if towing something heavy.

Last Friday I was headed up to northern Minnesota. Calm sunny day and I stopped into a truck stop to refuel because I was down to a quarter tank . The only pump available was for #2 diesel and I was in a hurry so I filled it. Normally I would have #1 in it during the winter months. On the way up I watch my mileage climb on the lie-o-meter up to 18, then 18.2 and then end up on 19mpg. I reset it several times and chose the 30 minute calculation vs. the 5 minute. The entire 4 hour trip averaged over 18.5mpg. Weird - I have never gotten this good of mileage ever with the 6.7.

On the way back it was down to a quarter tank so I filled it back up with #1 diesel and this time averaged about 17.5mpg.

Both days were calm and half of it is freeway at about 75mph and the rest is highway at about 63mph.

Im not complaining but what has changed? Is the engine wearing in and giving me better mileage? Is the #2 diesel really making that much of a difference? Tires are almost needing a change changing the final drive ratio? I'm puzzled but happy. 19mpg seems great and I have not even deleted yet. Any thoughts?

 

#1 diesel is a bit more volatile than #2 diesel mainly because its pretty much straight diesel fuel with very few additives other than Kerosene to help prevent gelling. which because #1 lacks some of the additives that #2 has so it flows a little more freely though the fuel system. but it has some drawbacks to it as well.. it doesnt provide the same lubricating effects you get with #2.. also youll get greater torque from #2 than you will #1.. #2 is supposed to have the better fuel economy. but every trucks different just as not each fuel mix is perfect either.

something else to consider is the Cetane rating.. many dont bother to look for this on the pumps (ntm often the pumps are incorrectly marked alot of times too).. fuel mixed to a cetane rating of 55 will run more efficiently than one with a 40 cetain rating. some stations will carry fuel in a certain rating depending on who their primary clients are.. for instance when the 6.0's were first designed they were programed to run what was supposed to be the new federal minimum mandate of 50cetane. This was supposed to be done to meet stricter emissions mandates meeting the European standards. When the measure didnt pass the stations continued with the 40 cetane and trucks had to be reprogrammed. about the equivalent of programming a sports car to run on 93 then forcing them to run on 87.. or in the eco cars programming it to run on 87 and then fulling up with 83e fuel. they just dont like it.. the higher the cetane the more efficient they can run.

the pump you probably filled up was most likely carrying a higher cetane rated fuel being that it was a truck stop.

 

 

Lol - screwing up the subject line is my speciality. Fixed

 

 

It would appear that fuel makes a huge difference - #2 is cheaper also. The problem is that it would definitely gel in the deep winter.

Would strait #2 plus a healthy shot of Power Service Products Winter Supplement work to stop the gelling when it gets down to -10? Any other risks in running #2 all the time?

 

Yes #2 with additive usually works at -10

 

Here is what #2 looks like straight from the pump at a Loves truck stop in Kansas during the January arctic blast. I ran out of Anti-Gel so this tank didn't get treated until I got back home.

 

 

Actually... this is incorrect.

• #2 has more BTU's than #1.
• The amount of additives doesn't contribute to volatility.
• #1 has a lower cloud and gell point than #2.
• You won't get straight #1 at any fuel station pump. Diesel fuel is either winterized (#2 with winter additives), or blended (a combination of #2, a small portion of #1, and winter additives).

Because #2 has more BTU's, that's what gives the better fuel economy. Adding #1 (blended fuel) typically causes a drop in fuel economy because there is less energy content (BTU's).

 

I agree it was treated or blended to some degree. As the image shows it was just starting to cloud, I always add additional anti-gel just to be safe. We don't have the option to pump #1 diesel down here in the southern states like those of you up north.

 

i was just going off the differences i found across several sites that compared #1 and #2.. they were they ones saying #1 was more volatile, along with being a straighter diesel fuel mix compared to all the additives they put into #2..

 

Some of the northern states do actually sell straight #1.. I've seen many pumps in Montana and North Dakota that are labled at #1, and right next to it are #2 pump as well as many that offer different percentages of #1 just like chosing Octane ratings on a gas pump. ie 100% #2 70/30 % 50/50%