Sorry i posted this in the wrong spot

If you call in advance and speak with the parts guy most ford dealerships will give you a big discount to buy FORD products I bought the FORD brand def for about 22 bucks for the 2.5 gal jug

 

But you should be aware that the DEF has both a short shelf life as well as is temperture and sun sensitive, and will not last in your truck as long as fresh fluid if it subjected to long storage, and or high heat.
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What I'm wondering is what happens if you get a really old refill. How does the truck know you've got lame DEF? And if it does, are you supposed to drain and refill? How much warning will it give before the truck goes into limp mode?

 

The truck monitors NOx reduction and if it does not see what it expects to see it will then let you know the DEF is not doing its job.

Yes, if you have bad DEF you have to drain and refill. Unfortunately the tank does not have any handy way of doing that, like a drain, so you have to siphon it thru the filler.

Im not sure on the exact details, but you have some time (at least a few hundred miles) before it goes into a actual limp mode (i.e. idle only). I do believe you are immediately limited to 55 mph though...

 

That's what I was thinking. I know some guys are carrying around a gallon in the back of the truck but that has to be a pretty poor storage environment. Just when they go to use it, it's going to be very weak or worse, useless. I'm at 5,000 miles now and my DEF gauge says less than half full. I think it would be wise to simply fill it up when it's at half level. That way I'll always have enough to get wherever I'm going.

 

IDS Techtips

I assumed that from this they could pump it empty?

Assume gets me in trouble too often though

A little information is sometimes dangerous.

Bob

 

I'll assume you are referring to where it talks about "SCR System Emptying"? If so, that would be better described as line purging and is a action that happens every time the truck is shut off. This would not be for emptying the tank, but it does keep the DEF from freezing in unheated lines in the winter...

 

I thought I read in the Diesel suppliment that there was a drain spigot for the DEF maybe I was mistaken - But I thought it was similar to the spigot on the fuel water seperator.