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Well, thats a relief, drove it yesterday, filled it up, and no seek repair lights. I was a bit concerned having only less than 4 gallons in it, took 3.75 gallons, and I think it holds 7? It ran GREAT!
My 24 drinks DEF where the 2019 I had sipped it. 23+ DO use more, at least 3 times, the amount of DEF that prior MY ones did, but it also doesn't dump fuel into the engine when doing a regen.
Word on the "premium" def. This is intended for people like me who seldom drive the truck and it tends to sit for long periods of time. THats when DEF can crystalize in the system.When driving, the system is active and pumping DEF to the SCR, so its always getting fresh DEF through it. As long as you have constant use of the DEF system, there really isn't a need for the additives, only when you park it for any length of time is it required.
SInce I haven't driven mine for like 5 months, going on 6, I should probably go fill the DEF and put some miles on it to flush the system as well as add some of that decrystalizing medication you talk about. I still have to get it safety inspected too.
Originally Posted by acdii
Well, thats a relief, drove it yesterday, filled it up, and no seek repair lights. I was a bit concerned having only less than 4 gallons in it, took 3.75 gallons, and I think it holds 7? It ran GREAT!
The 11 to 16s have 5 gallons. Not sure about the pre 20s, but thought I read the 20s and up, or maybe the 17s are included, have 7 gallons.
I had started buying the Platinum Blue myself due to the miles on my truck and believe that was prior to the job of replacing the bad DEF pump and also the sending unit/heater due to the miles on the sending unit... did not want to have to drop the tank again later on if that second unit went bad...
After that, heard about the Defender additive from Hot Shots, bought it and then after I finished the Platinum DEF, started buying Wally World Super Tech jugs for cheap... added the Defender additive, 1 Oz per 2.5 gallons and still have some left. It's also supposed to lower the temps of DEF freezing point...
Just FYI.
Hot Shot’s Secret Premium Defender DEF Booster Additive 8 oz – Treats 20 Gallons – Diesel DEF Treatment for Diesel Exhaust Fluid, Cleans and Prevents Crystal Build-Up https://a.co/d/0h4AV6Cx
iirc i thought our def tank was 7 gallons
but i have slept since then
if i am in low 50% def and add 2.5 gallons it brings up to 90-97% on def reading in IPC
my truck loves def in traffic, but once your up and going at highway speeds it sips it as in miles and miles before it need refill
towing the boat at highway speeds it uses a few percent every 100 or so miles, but caught in some stop and go or under 50 mph for a bit and it guzzles it fast imo
Well, thats a relief, drove it yesterday, filled it up, and no seek repair lights. I was a bit concerned having only less than 4 gallons in it, took 3.75 gallons, and I think it holds 7? It ran GREAT!
Good news!
At 7.5 gal a DEF tank at 66% should take a jug (2.5gal), but in my case, if I don’t wait until 62%, the tank overflows. At best I get about 450 mpg.
Apparently DEF is most stable a couple degrees C below zero. I assumed evaporation was the cause of crystallization. It’s not. The solubility of urea is quite high (depends on temperature, but something like double the 32.5% in DEF). From what I read as the temperature goes up (high 80’s F), DEF can break down into other compounds that crystallize (I didn’t understand 1/2 of it!). The main ingredient in one DEF additive I looked at is Hexyl-D Glucoside, a dispersant mentioned in pharmaceuticals. Presumably it’s what disperses the crystals. I think if I was in a much hotter climate and didn’t use a lot of DEF, I’d be looking closely at using a DEF treatment.
Last edited by Gladstone; Jun 7, 2026 at 10:19 AM.
At 7.5 gal a DEF tank at 66% should take a jug (2.5gal), but in my case, if I don’t wait until 62%, the tank overflows. At best I get about 450 mpg.
Apparently DEF is most stable a couple degrees C below zero. I assumed evaporation was the cause of crystallization. It’s not. The solubility of urea is quite high (depends on temperature, but something like double the 32.5% in DEF). From what I read as the temperature goes up (high 80’s F), DEF can break down into other compounds that crystallize (I didn’t understand 1/2 of it!). The main ingredient in one DEF additive I looked at is Hexyl-D Glucoside, a dispersant mentioned in pharmaceuticals. Presumably it’s what disperses the crystals. I think if I was in a much hotter climate and didn’t use a lot of DEF, I’d be looking closely at using a DEF treatment.
yup me to
if i add the 2.5 jug at any level above 55 to 58 it will overfill and spill
i used to carry a jug in the tool box.. but now i dont worry
i am getting more and more just drive it like its wanting to run and enjoy the ride
yup me to
if i add the 2.5 jug at any level above 55 to 58 it will overfill and spill
i used to carry a jug in the tool box.. but now i dont worry
i am getting more and more just drive it like its wanting to run and enjoy the ride
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