I'm not sure exactly. I bought this truck around 2 months ago from an out of town dealer. Had 110k on it, probably only 112k now. We drove it home 3-400 miles. Fuel seemed great. I love the truck etc. Forward to now, saw the first exhaust regen cycle begin, never saw it end and I might be crazy but am I stuck in a cycle and using a lot of fuel? Is that something that could even happen? I understand you need to allow it to finish on a highway at 65mph etc. I am new to the whole DEF garbage etc. This is not a truck I haul a trailer with, not a work truck, a somewhat daily driver and many long distance trips out of state etc, however, it is on the highway a lot, so you would think it would finish the cycle? Anyways, worried something is up! Getting 16-18 on the highway, but it seems like it is lying!

 

Your not in a continuous regen cycle. 16-18 sounds pretty good to me, and pretty normal for my 2015. All these old geezers in campgrounds bragging that their Rams or powerstrokes are getting 22+ mpg are full of poo poo.

 

You can get the exhaust filter soot % screen enabled to show you when it is getting ready to regen and then watch it count down the soot % when It does.

If it is already added you can check by going to the screen that shows the engine oil and trans temp and then scrolling further. If it is not you can get it enabled at a dealer or with forscan.

How fast are you driving? Slow down a little and it will get better.

 

So the computer says 16-18 MPG and you think it's wrong? Why do you think it's wrong? Have you tried hand-calculating the mileage?

Fill the tank up, reset the trip meter, drive until it's empty and then fill the tank back up. Whatever you put back in is the amount you burned and you can calculate your MPG from that. My guess is, you're getting 16-18 MPG and you're just not used to the smaller fuel tank in these trucks.

 

I am most likely comparing apples to oranges. Coming from a Dodge Ram 1500 (Gas), seeing the same MPG but filling up at the pump more. F250 is a heavier/bigger truck etc. I had a 2008 F250 Harley several years ago, so no experience with DEF till now.

I've been at "below 1/2 full" on the DEF status messages since I purchased the truck and have no experience with the DEF system, so somewhat natural to worry that something might be wrong. I am coming from a 25-gallon tank on the Ram too.

 

I fill the DEF about every 5K miles with a lot of towing.

Less towing equals less def useage.

 

When I had stock tires (275/65-R18), the computer was over 99% accurate. With 295/70-R18 it's off some. A full active regeneration will subtract about 0.9 MPG from the total tank.

Your 16-18 MPG is great. 14.9 MPG is the closest I've been to 15 MPG this year. This is hand calculated. For the most recent example, the computer reported 12.8 MPG.

12.7
12.6
12.8
14.9
13.7
12.3 T
14.4
13.6
13.4 T
13.1 T (most recent)

 

How do you get the mileage that low? Short trips? Crazy speeds? Other? I can only get that low with a trailer connected.

 

295/70R18 is a 34.5" tire.

I get 14.2 average with 35x12.50s. Tire size makes a big difference.

 

My Jenny Craig 15 with 3.55 rear end will consistently get 19.5 to 20.5 on the highway, this is with the cruise set at 110km/hr or just shy of 70mpg. Worst I ever see is short trips in the city during winter in central Alberta and that will be around 15mpg. Before the diet the best I ever saw was 18.5 and that was cheating by resetting the mpg right after a Regen finished, all highway again at 110. This was with stock 20" factory Michelin's and no trailer of course.

 

That is a mix of 45 and 55 MPH with some traffic lights. For a regular weekday, around 40 miles total /day. The "T" is towing and that's mostly 55 MPH highway with half the trip rolling hills, typically around 170 miles at 15,500 lbs. The weight doesn't change much.
Two specific firmware updates over the years (one was specifically labeled emissions if I am remembering correctly) reduced the MPG by at least 1 MPG total and the rest are from the heavy tires.
The truck used to average 15-16 MPG with 295/70-R18 Nitto Terra Grapplers in 2012 but it has been slowly decreasing over the years. Toyo OC AT II lowered a bit more and the current Cooper Discoverer S/T MAXX reduced again by about 0.4 MPG. The tires are for purpose and not for show so it's the cost of having them.

Edit: I forgot an important factor. The Cooper tires were in March and I mounted a < 350 lbs ranch hand bumper a few weeks after that, which contributed to this current lower MPG.

 

My lifetime average is 12.4 mpg. Due to a lot of towing and the DRW.

For the record it is better than my 08 but not much. I had a lifetime of 11.5 on that diesel.

 

I am not running on the stock tires, I forget the exact details but they are Toyo Open Country. So that might explain the MPG being off (maybe). My driving habits are not speeding, I am usually 5 above the speed limit on the highway so usually, 65-75 depending. I don't accelerate it fast etc. Drive it more like an 18-wheeler lol. I am not in any rush, taking longer to get there just means I get to enjoy driving my truck more. Being about 2 months old (for me) now, just found out the front 2 shocks are shot and hub bearings are needing to be replaced. OUCH on the wallet. But I rather know and get it fixed then find out while traveling. Buying a used truck you really don't know how the previous owner took care of it. The truck is in great shape outside and perfects inside. Just you never know if they kept up with things. Slowly taking over knowing that by doing what I can on my own and paying someone else to do it when I can't. Eventually, I'll know everything going on with the truck when the last whatever was done etc.

Today I went to the dealer because the "Check Coolant Additive" message came up. They wanted $450 to do a coolant flush! LOL ... Um no... Went to a trusted mechanic instead (used em several times), $99 for the flush plus coolant. Dealers are crazy!

 

check coolant additive does not mean you need to change it. Check the maint. schedule. Did they put in the proper coolant? What is the color of it? Also watch the level it may need some added if there were any air pockets.

 

For what it's worth I get 17mpg on the highway @ 70mph unloaded according to the computer. 2016 CCSB FX4 3.55's and 20" Toyo Open Country AT's. @ 80mph that drops to 15mpg and @ 55 it's around 18mpg, I'm not patient enough to drive that slow so don't have any real good data. Towing a trailer I get 10mpg.

That flush and fill sounds cheap, The Motorcraft Orange Coolant is almost $30 a gallon. It was probably due for a coolant change anyway since it's supposed to be flushed and refilled around 100k.