My truck gave me the message that "DEF under 1/2 full", so since we are on the road, I stopped by a dealer and picked up 5 gallons of motorcraft DEF. I did not want to get the countdown message in an unfamiliar area and have to look for it. While going out site-seeing, I forgot and left it in the back seat of the truck for about 8 hours in the heat of the day. I know you are supposed to store it under 86 degrees or so. Now, did I just ruin 5 unopened gallons or is it still safe to use? Thanks in advance guys. P.S. Getting older sucks, i guess the memory is the first thing to go!

 

I doubt you ruined it - it reduces the shelf life, but if you are using it you should be fine. Also, even if the DEF is not as "fresh" or "strong" the truck will just use a little more of it. There is a threshold where it sets the contaminatd DEF message. I have no idea what that is. If it makes you feel any better, I see the bulk DEF storage tanks outside at gas stations. I wonder how that heat affects it or if I am missing something and they are temperature controlled.

Just my .02. Oh and I have kept DEF in Miami for months in an un-air conditioned garage and it was fine. That DEF has long since been used up.

If you are ever concerned about DEF there is an under $20 tool from Amazon that will test it. Thanks to a user on FTE that suggested it in another thread- it isn't my novel idea.

 

Run it. You are fine.

When I am on the road I put it in my tool box.

 

Stop and think about it for a few minutes. When you put DEF in the trunk DEF tank, does it not sit in the sun and heat for hours on end? Maybe weeks or months before it is all used. You are worrying over split milk as the old saying goes. Use it. You will be just fine.

 

Next January-Febuary we will be reading about -34F and Frozen DEF.

 

Hell my truck sits in 100+ degree heat all the time. So far no problems with def.

 

I too have wondered about this. In my case I purchased a jug of DEF from my dealer, now over a year ago. It still sits unopened in my toolbox, stored outside year round. While it doesn't get too cold here - summer times do get pretty warm.

 

Thanks everybody! I will put it in once I get the countdown. Was just a little worried because everything is so expensive to repair on these trucks and it seems one little error can result in a warranty denial.

 

Yup, that is why you have a heater in the DEF tank....and also should NOT add DEF until you are sure the tank/fill hose are thawed....

 

It's funny, but I got a countdown in the cold and this was when there was no "heated" garage for my truck. It was entertaining and slow to get enough DEF and I didn't right after a drive so everything should have been warm.

I also don't like to fill it in those conditions either. Even though I know that it's designed to not be overfilled.