Reading on here (for several years) about waiting / not waiting for the 200 mile DEF warning I had plans to wait.

At the 299 mile warning I purchased 5 gal (Walmart Supertech brand).
At about 290 miles I saw an additional line - saying fill up now, so I did.

The truck consumed the entire 5 gal. of my purchase - and when I fired the truck up the warnings were gone and the truck said the DEF level was OK. There was no need to run it several cycles to clear the messages.

First DEF refill - just past 3400 miles on the clock.

 

On my 2015, I have partial filled my DEF when it says the level is OK or Less Than Half and have never had an issue of the DEF not resetting to full.

 

Same, my 2016 has been flawless when filling at the "less than half full" mark. In my opinion those that recommend filling after the tank is near empty is limited to the pre '15 trucks.

 

Had a ‘15 F250 SRW and now the ‘18 F350 Dually and I know the DEF tank is at least twice as big in the F350.

 

DEF tank capacity in the 2017+ is 7.4 gal for the pickup frame.

 

On my truck, I've filled it after it hit the 500 mile warning a few times. Once it went below 500 and the other just after the warning came on. But I have also filled it without getting the 500 mile limit warning and have not had problems with it resetting also. I've never checked and seen the DEF below half warning though. I'm waiting now to see it as the DEF is around 67% last time I checked on my iDash. I don't tow so mine goes out to around 7k ish to 8k miles.

 

I didn't know that, I thought it was close to the 5 gal mark as many have stated they had DEF leftover.

 

Hey Army RET, nice looking rig there, sir.

 

Danka, we like it.

 

I've mentioned before that I don't know why the gauge is marked in 1/4 tank increments, when the tank is 7.5 gallons and the jugs at the store are 2.5 gallons. When I look at the gauge I just imagine it in thirds and buy two jugs when it's 1/3 full..
I've only had a mild scare once - during a long run in winter I let it get low enough to warn me to fill up soon and was nowhere near civilization. By the time I got to a WalMart it was threatening to reduce power if I didn't fill within 50 miles (IIRC). I bought a couple jugs and poured them in. When I started the truck the gauge did not reflect the added fluid and continued to warn of imminent power loss. Concerned, I pressed onward. As I drove, the fluid level indicator very slowly rose to nearly 3/4 full, but the warning continued to count down. At this point I was very concerned and pulled into a rest stop to ponder my options. Since my only option seemed to be going forward, I started the truck. The "needle" snapped to position and the warning vanished. All was right with the world. It never happened again, either. Even though the DEF tank is heated, I'm guessing that it was so cold the heater couldn't keep up and at least some of the DEF was frozen, causing problems with the level sensor and once everything was thawed and the key was cycled it all returned to normal.
The pump/heater is also cooled by the fluid in the tank. Allowing the level to drop exposes the pump/heater assembly to air which doesn't cool the motor nearly as efficiently as fluid does. Allow it to drop too low and (I believe) you run the risk of damaging the pump/heater assembly. Accordingly, whenever I reach 1/3 tank I buy two jugs and fill it back up, except in winter when I try to leave it about 1/3 tank below full to allow for expansion if it should freeze.

 

If I read that correctly, I'd say the 17s+ have a DEF level gauge which is pretty freakn awesome. The extra 2.5 gallons is nice also.

And if I never told you thanks for serving Army RET, thanks for serving brother. Much respect...

 

And if I never told you thanks for serving Army RET, thanks for serving brother. Much respect...

Wish I'da heard that back in the early 70's - when we were called baby killers. Old history.
Now I simply grin and collect my monthly check.

 

I'm only 52 so too young to remember that but I've heard the history about it. Problem is is those flaming libtards from back in the day are now teaching all the young minds in college... but that's for another discussion. I've pulled combat vets over just to shake their hands. I once pulled over a WW2 Purple Heart Recepient just to shake his hand and thank him for his service. It's a big deal for me to go out of my way to thank vets and current military members. I have A LOT of respect for you guys.

 

Have you guys waited till it went to the 500 or 200 mile warning to see if you experienced an issue? Thinking of you always fill it at 1/2 or more, you'll never know if you've confused the DEF system or not.

 

Army Ret, I don't want to drag this thread down a rat hole, but have to comment, I am the correct age. Tricky Dick saved my life, they did the lottery in 1972 for the class of '73, my number was 4. While I vehemently opposed the south east asia police action and protested hard against it, I always advocated for the folks that had to deal with that BS. A number of my friends gave the ultimate sacrifice. For those that don't know, people would sacrifice their kids, they would strap explosives to their body, have them walk up to a platoon of American soldiers with their hands in the air, when the kid got close enough they would explode the the kid. Like 7 year olds, it was an awful awful situation and those that were there should be honored to the highest extent.