Draining old DEF fluid?
Lead Driver
Joined: Dec 2020
Posts: 8,640
Likes: 2,435
How long is a long time?
I'm sure it's fine. Unless it throws a code there is no reason to worry about it. Doesn't matter if it's 1/3, 3/4, or full, it actually lasts quite awhile. In my 2019, because of how few miles I put on the truck (approx 4k/yr), I only add one 2.5g jug in per year. I wait till it shows 1/4 and then add the 2.5g which then shows 5/8 on the gauge. Haven't had a problem yet.
If dead set on removing the DEF, siphoning seems to be the suggested method based on other threads.
I'm sure it's fine. Unless it throws a code there is no reason to worry about it. Doesn't matter if it's 1/3, 3/4, or full, it actually lasts quite awhile. In my 2019, because of how few miles I put on the truck (approx 4k/yr), I only add one 2.5g jug in per year. I wait till it shows 1/4 and then add the 2.5g which then shows 5/8 on the gauge. Haven't had a problem yet.
If dead set on removing the DEF, siphoning seems to be the suggested method based on other threads.
Cargo Master
Joined: Jul 2003
Posts: 3,361
Likes: 250
DEF lasts longer than a guy thinks. I asked a pretty good heavy diesel mechanic and he said the thing that kills DEF the fastest is exposure to sunlight and extreme heat. Unless the DEF was a couple years old I'd just add fresh to the tank and run it.
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