Are you on your 3rd fill up of DEF or 3rd time you added 2.5 gal?
The tank holds about 5.5 gal's.
I am at almost 6000 miles and have not had a low DEF warning yet.
With that said, It will probably come on in the am when I start my truck...lol

 

3rd time adding DEF first was a complementary single gallon at 1k miles by the dealership then I added 2.5 gallons at around 3k miles when DEF reading was 27% and I'm about to add another 2.5 gallons after my 260 mile treck to denver on friday. currently my DEF reading is 25%. So Friday/Saturday will be my 3rd fill up

i guess I'm wondering if I'm prematurely filling it or not?

 

As I understand it, the DEF should be used at about 2% of your fuel rate. So for every 100 gallons of diesel, the truck should use about 2 gallons of DEF.

I haven't paid much attention to how much mine uses. Doesn't feel like too much, maybe 8-10 gallons over 15k miles?

 

As I understand it, the DEF should be used at about 2% of your fuel rate. So for every 100 gallons of diesel, the truck should use about 2 gallons of DEF.

This is consistent with what I've seen. I have 10k mostly highway miles, and have been using 1 gal of DEF per 54 gal of diesel if not towing. When towing, I've used 49 gal of fuel per gal of DEF. This works out to 1100 miles per gallon of DEF when towing and 1400 miles per gallon of DEF otherwise, or in other words one full tank of DEF every 5000 - 7500 miles: pretty much exactly what GM says to expect.

 

You're putting in 50% of the tank's capacity when you're 70-80% low, so you're adding (less) more times than you would be if you actually filled your tank, i.e if you put 15 gallons in your fuel tank every time your 20gal tank is empty, you're gonna make more trips to the fuel station than everyone else who fills their tank when it's empty.
FWIW, I got through a tank every 5k miles or so

 

Dealer never topped off upon delivery of truck. took it into the dealership for is first oil change prematurely at 1000 miles. At about 1500 the truck gave me the 30% warning on def. Bought one of those 2.5 gallon blue def and it didnt take it down all the way i maybe had that .5 gallon left. Drove from Miami to Virginia and back non stop and as able to pour in the remaining .5 left over of def. Im just shy of 9000 and due for an oil change based on my instrument cluster (5% left) and it still says DEF ok im currently at 9000 miles

 

I'm at roughly 1 gallon of use per 1000 miles.

 

As a newbie here , at what point does the DEF level on the DIC change from Ok to a percentage ?

 

30%.

 

I was wondering how low of a percentage any of you have seen without running into problems. I just hit the 30% mark This is on a tank that I filled right up and I went 14,000 kms on that tank so far. I went out to the DEF pumps but turned back because I want to see the true mileage from full to empty. Is there a known number where I really need to fill Iit up such as 10% ?

 

If you still have your diesel supplement book, on page 42 it starts describing the DIC messages you should see as the DEF gets lower. This includes up to reducing your speed to 8 km/h if you let it get too low!

 

DOn't know what you guys are doing to your trucks but mine just turned 10k and at 5k it took 2.5 gal and at 10k just a little under 2.5 gal. I don't baby mine either

 

DEF usage is roughly 2% of fuel consumption, or about 50-to-1(you'll use roughly 1 gal of DEF for every 50gal of fuel burned), so the higher mileage you get-the more you 'baby' your truck- the less DEF you'll use.
Since you say you're using about 50% less DEF than most others, you're driving it like an 80-y/o woman drives her 1992 Honda Accord.
Have you had your testosterone level checked lately?:grin2:

 

Wally World has Supertech DEF for around $8.00 per 2.5 gallon jug, which is the best price I have found. Some carry Dexos2 oil too, mine does not yet, but I am hoping.

My understanding with DEF is that the more the engine is set to use, the less EGR it needs to meet emissions. 1 gallon per 1,000 miles sounds like pretty light DEF usage. I would not mind buying DEF more often if it would minimize or better yet eliminate EGR usage, as the engine would not have to breathe it's own exhaust and it's combustion would also be more efficient.

 

Perhaps a dumb question but I know DEF has a shelf life. The jugs I found at Walmart have a date on them. Does anyone know if that is the expiration date or the manufacture date? The ones I saw were dated Feb 2017.

I switched over from OK to 30% on a trip today and within 200 miles is already to 26%. Should I wait so I can fill fresh instead of half?

I just tripped past 2,500 miles so my dealer shorted me too I guess.