I am getting ready to buy some DEF. It seems to be sold many places.

The Super Duty owners manual says only to by API certified DEF.
Are there some brands to stay away from? (some that are not API certified)

All the containers with dispensers seem to be a basic flexible plastic tube.
Is there a preferred dispenser I should be looking for?

I see many offers for (2) 2.5 gallon containers, that is less expensive than buying smaller quantities. The discoverDEF website says shelf life is 2 years. How much can I expect to go through?

The manual says the DEF tank is a little over 7 gallons. I thought I read somewhere that the DEF gauge is not precise. Also, I thought I read somewhere that you generally only want to fill the tank to 2/3 full. How can you control how much is in the tank if the gauge has a vague readout and the dispenser is manual?

The manual mentions cold weather, and a preheater, and makes a cautionary reference for those vehicles that sit unused for any length of time. It is possible I may not use the truck for a few days during the period of cold weather it is warning about... is there something I need to do before attempting to start it up to get the DEF tank preheated?

 

There are only a few DEF producers out there. MOST are just released. I get mine at the pump and refill 2 2.5 gallon containers I keep in my garage.

Buy the Ford DEF nozzle for $8 at the dealer. It will prevent you from overruling and spilling down the truck. It screws on to all the 2.5 gallon jugs.

I get about 6,300 miles out of my 5 gallon tank.. you should see mid 7s ( every oil change) with the larger tank if you don't tow frequently.

 

milkweed, DEF is 1/3 urea and 2/3 de-ionized water. This stuff is not rocket science, and it does not go anywhere near your engine. Just sprayed in your exhaust system. DEF does "expire" so check the dates on whatever you buy. Otherwise, I'd not really care what brand I got.

Worst that can happen is a message about "low quality DEF" and perhaps a Check Engine light signifying emissions are not being met. When this happens, absolutely nothing has gone wrong with your motor. Its just a precaution forced by the EPA so you can't pour straight water into your truck to 'fool it.'

DEF lasts best when kept at a cool-ish temp of 60 or so degrees and not in the sun.

I don't think the DEF gauge is precise. It uses electrodes on the wall of the tank to "judge" usage. When the level hits a certain electrode, the gauge should be spot on at that point, and then 'estimate' until it hits the next one. There's probably three or four electrodes.

DEF does freeze at 12F. If your truck sits overnight in temps below 12F, its likely your DEF will be frozen. In this case, the truck doesn't care. It starts and runs fine without DEF, because its knows it is frozen.

These trucks have an electric heater in the DEF tank, DEF pump, and the DEF hose line over to the injector in the exhaust. Once the truck starts, these electric heaters will start melting the ice. In a certain period of time, it will be liquid again and start injecting again. Keep in mind the DEF heater system is monitored, and a failed heating component will result in a Check Engine light being set.

How long the DEF lasts depends greatly upon how you use your truck. The general rule is the harder you work it, the more DEF you'll use. No matter what, the 7 gallons should last about an oil change. On my dually, with quite a lot of towing between the last oil changes, the gauge indicated I used about 4/5ths of the DEF or more and I had the countdown warning telling me I had less than 500 miles until the DEF ran out.

 

I buy it at Flying-J/Pilot truck stops (it's in most fuel lanes now, look for a sign hung above). It ranges in prices around the Country, but usually ~$2.49/gal via the bulk dispenser. One stop I got it for in Texas for $1.79/gal

BTW- Your truck will drink DEF much much quicker when towing or hauling heavy. In my case of hauling around my 21K-lb tin can, a full DEF tank can be emptied in as little as 2K miles.

 

I've got 6400 on mine and have added 12.5 gallons. It is mostly full now and the guage read full when I bought the truck new at the dealer. Most of those miles have been pulling a 9,500 lb TT so towing will slurp up the DEF.

 

Very true. I am towing a similar load as you and I got my first 500 mile warning at about 4500 miles on the odometer. I got some "Blue" DEF from a parts store (which had the proper ISO rating) and dumped it in. I did not fill it this time around. I will admit, it did go a bit faster than I expected but I do tow quite a bit.

 

I have not had to put any DEF in this truck but in the past I have always used Wal-Mart super tech brand. It has all the ratings, a date sticker to be sure you're buying fresh DEF and the hose for easy filling. Plus, it's only $8 for 2.5 gallons. It's cheaper than Blue but not as cheap as what you'll get at a truck stop.

 

I just picked up 2ea 2.5 gal jugs of Peak Blue DEF at Sams club today for $10 each.

I add a 2.5 gal jug when the def gauge shows 1/2 full.

A 2.5 gal jug gets me about 2000 miles towing a 14000 lb 5th wheel 30% of the time.

 

+1 A lot cheaper to pump yourself at the truck stop and you don't have to worry about storing it or the smell. Just have to remember that you can't just buy DEF at the pump. You have to dispense some diesel first.

 

There are *zero* DEF pumps in VT or Maine, and only in one NH right at the coast and unfortunately several hours away from me. So unless I happen to be traveling, I'll end up having to buy the jugs.

 

troverman,
u continue to amaze me!!!!

 

Thanks Skip. Mostly I like to read about this stuff a lot, and a lot of knowledge is from other members who are a lot more knowledgeable than me.

One correction; it appears if you are towing very heavy you can run your DEF out well before an oil change. I would also say this 2017 truck uses more DEF than my 2016 diesel did.

 

My 2017 truck also uses more DEF than my 2015 diesel did.
Regards,
Skip

 

Troverman is a vessel of knowledge!

 

Tried to give you reps for that, RJC2...but the rep gun is unloaded! Thanks.