6.7 only has a 5 gal def tank. my neighbors 4cyl MB SUV has a 7.5 gal def tank. Just wondering how often the Ford def tank needs to be refilled? Dave

 

Depends on how you use the truck, I tow heavy a LOT and get about 4600 miles to a tank of DEF.

 

I've never wanted a larger DEF tank. I could fill my tank at every oil change (5-6,000 miles) and would never run out. Plenty of warning messages too when you get low.

When I purchased my truck I had a concern about DEF but a post on FTE told me to fill the tank and don't worry about it. The person that made this post is correct. I never worry about DEF or carry extra now that I've had the truck 2.5 years and 28,500 miles. Every few months I go out and see how much I can fit in the tank. Then I forget about it.

 

Yeah. Don't worry about it Dave. I can haul 5 small cars on one trailer (grossing nearly 30,000 pounds) all the way from NH to OR and fill it when I leave NH, fill it when I get to OR. (2014 F-450) And even then I've got some miles to go.
It warns you when you have 500 miles to empty. And if you're ever curious, you can check the status of the tank at any time through the cluster.
And if you're STILL worried about it then you can swap in a Chassis cab tank at 6 gallon cap. Although I'm not sure that this is a R and R swap...

 

I fill mine every oil change. About 25% of my mileage is towing. Have never gotten a message that it's too low. It will stay on the 1/2 full message forever.

 

I've never worried about DEF in my '12... After reading all the horror stories about trucks shutting down and whatnot I decided to run a test and see how many miles I get from full to the first 1/2 full warning.... so far 4900 and change miles and counting... That's a fairly even mix of town, highway and towing a 12K 5'er...

 

The more you tow, the more DEF you use. Towing through the Smokey's for a few weeks had me using quite a bit of DEF. I just refilled at the Pilot stations in the Big Rig fueling as they have DEF at the pumps.

 

What's DEF?

 

Most of my driving is in the city in heavy traffic, and I still get more out of my DEF than oil. I'll let the gauge drop below 500 MTE before refilling unless I'm traveling.

 

Ditto here. I have never received the next message after "less than half full."

 

I get between 5k to 6k depending on how I use the truck during that tank. It's nothing to worry about.

Funny.

 

I never carry extra DEF. Around 80% of my miles are towing a heavy fiver. When I am less than half full I buy some DEF and add it.

 

I simply wish the DEF guage had a bit more reading than above 1/2 or less than 1/2. It could at least be measured in quarter increments.

 

I agree.
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Yes, would be nice if there was a real gauge, but even the Ram guys who do have a gauge aren't happy with the way it works.

At least the low DEF warning gives you 500 miles advance notice of the tank being empty. I am always able to get to a DEF pump well before running out.