Replacing old DEF in Truck?

[Ugeesta]

Bought my first diesel in July last year so I’m still learning the joys of owning and maintaining the Diesel engine. I understand that DEF has a shelf life and reading about it on line, it appears to have a 1 to 2 year shelf life if stored properly. But what about the DEF in the truck that is exposed to the temperature swings through the year?

My truck is 6 months old and has about 3,750 miles on it. It is primarily used to to pull our toy hauler so it doesn’t get a lot of miles in the off season. When searching for the truck, I had a dealer tell me that the DEF would last about 6 months in the truck so if it were to sit, only fill it half way.

My truck currently stated the DEF tank is at 26% capacity. Should I siphon out the old DEF and replace it with fresh or just add a 2.5 gallon hug of fresh DEF and not worry about it.

The concern is I would prefer to avoid costly repair bills if the DEF goes bad from lack of use.

Thanks.

[Midnightmoon]

I think that you have more chance of issues trying to siphon out the old instead of just topping off with fresh. It would be different if you were sitting there with a full DEF tank for several years. With the little you have left, just top off with fresh and go.

[Lake Huron]

Run it. I filled my Duramax last summer and all it does is pull my 5er too. Its hibernating for the winter right now and I've never had a bad def message come on. Mine gets filled about once a year.

[Stingray75]

No lights, no warnings, no issue - run it. I’d hold off adding fresh DEF until the DIC says it’s time then only one jug given the few miles you drive.

[putz]

Below is a Youtube video on removing the DEF. This is for a RAM.

https://www.youtube.com/watch?v=JCBetHI-AiY