# DEF Consumption



## MP81 (Jul 20, 2015)

It is kind of annoying that it doesn't give you a level above 35% full, but it's probably due to it being unable to measure it actively, if I were to guess.

I'm going to assume the tank is smaller, but I can't say for sure as I have not seen any mention of its size. Given that the smaller engine (with a half-point lower compression ratio) should put out less NOx emissions, DEF usage should decrease somewhat from the 1st gen CTD. And considering the tank is no longer able to use the massive expanse that would be the spare tire well, it more than likely has to be a lot smaller.


----------



## Tomko (Jun 1, 2013)

A couple of things that may help understand this situation:

1) DEF, like washer fluid and gasoline, is considered a consumable. And as such the reservoirs are not shipped from the assembly plant full. Only a nominal amount is supplied to allow the vehicle to operate during the delivery process. I suspect this has as much to do with shipping weight as it does with plant time and cost. It is the responsibility of the dealer to fill these reservoirs as a part of the pre-delivery inspection. But as we've seen, and especially for DEF, it is often 'missed' by the tech assigned the PDI. 

2) The DEF level indicator is programmed by GM to show OK until the level drops to 35%. GM does this on all of its diesels. DEF has a limited shelf life of approximately one year. Once DEF 'goes bad' it will not fully treat the emissions and will set a code eventually preventing the engine from running in any useful way, in accordance with emissions regulations. I suspect that GM uses this OK until 35% level indicator as a strategy to prevent owners from needlessly topping up their DEF and causing a situation where the quality of the entire tank of DEF has deteriorated to a point where it can no longer properly treat the emissions and cause the vehicle to go into limp mode. The analogy I'd make is of someone who never lets their fuel tank drop below 1/2. At best, they're only ever driving around with 1/2 tank worth of fresh fuel, diluted with 1/2 of stale. Repeat that over and over for two or three years and you've got a problem with any perishable product.


----------



## boraz (Aug 29, 2013)

youre overthinking it

fill it at OCI and drive


----------



## johnmo (Mar 2, 2017)

boraz said:


> youre overthinking it
> 
> fill it at OCI and drive


Well, yeah, I'll fill it and drive. We have a Flying J with DEF at the pump and it's on an alternate route for my usual commute, so that'll work out. Just wasn't figuring to fill it quite that often.

What's OCI?


----------



## boraz (Aug 29, 2013)

johnmo said:


> Well, yeah, I'll fill it and drive. We have a Flying J with DEF at the pump and it's on an alternate route for my usual commute, so that'll work out. Just wasn't figuring to fill it quite that often.
> 
> What's OCI?


oil change interval

gen 1 tank is large enough to last thru OCI, just wild guess the gen2 is as well

even if not, 35% is lotsa fluid left, not gonna be stranded


----------



## Cruz15 (Mar 17, 2016)

What Tomko said and I can go 11,000 kms and still have way over 1/2 tank. Gen 1


----------



## mkohan (Dec 19, 2015)

Maybe it didn't come from the factory with a full tank. Does anybody know the capacity of the DEF tank on the Gen2 models? 3,8 gal


----------



## Jetblast33 (Mar 12, 2017)

I'm at 3600 miles and mine just went to 33% , so added 2 gallons. Yes 3.8 is the capacity. Maybe not topped off when purchased.


----------



## LiveTrash (May 24, 2015)

I read an article that says the Gen 2 Diesel may need a DEF fill-up every 4,000 or 5,000 miles. I've worked it out that on a completely full tank on my Gen 1 Diesel (17 litre tank), I can go about 12,400 miles. My large work truck burns about 4 litres of DEF every 620 miles. My Cruze gets a little better mileage on DEF than it, so it seems appropriate.


----------



## johnmo (Mar 2, 2017)

LiveTrash said:


> I read an article that says the Gen 2 Diesel may need a DEF fill-up every 4,000 or 5,000 miles. I've worked it out that on a completely full tank on my Gen 1 Diesel (17 litre tank), I can go about 12,400 miles. My large work truck burns about 4 litres of DEF every 620 miles. My Cruze gets a little better mileage on DEF than it, so it seems appropriate.


I haven't seen the article, but I have seen the Gen 1 DEF usage number around 10k miles or so, which is why I thought it was possibly a little premature for my Gen 1 to be nearing a fill-up. I'm sure they've had to up the DEF usage to stay compliant with the EPA requirements. Thanks.


----------



## Jetblast33 (Mar 12, 2017)

Just a heads up, my DIC showed 36% today so topped off with exactly 2 gallons. Purchased at the local truck stop for 2.79 gallon. So far I have added 4 gallons since new and I'm at 5200 miles.


----------



## johnmo (Mar 2, 2017)

Mine was down to 11% when I had my oil changed at the dealer today. They topped it off, though the service ticket says "2." It's not very specific about what I got 2 of, but I'm guessing DEF. Gauge shows "OK" now, but I doubt the tank is full based on what others have said about it.


----------



## johnmo (Mar 2, 2017)

I didn't make it to my next OCI before needing DEF. It seemed to kind of suddenly need filled because I don't remember seeing any notifications before it started reporting under 300 miles remaining.

Filled at a truck stop for $2.79/gallon and it took 2.8 gallons to bring it up to full from about 9% remaining. No big deal except the truck stop is on the long-way home.


----------



## TX CTD (Oct 24, 2014)

I could read the tank level with my OBD2 scanner on the Gen 1 diesel. I bet you can do the same on the Gen 2 cars. I haven't looked to see if I still can now that it's deleted, the DIC just says the level is OK.


----------



## PanJet (Jun 18, 2013)

TX CTD said:


> I could read the tank level with my OBD2 scanner on the Gen 1 diesel. I bet you can do the same on the Gen 2 cars. I haven't looked to see if I still can now that it's deleted, the DIC just says the level is OK.


Gen 1 here.

It's been a long time since I've looked at it, but if I recall correctly on my Scangauge, the DEF level always read 100% until it reached 35%, then started dropping.

Aside from smaller reservoir (Gen 1 = 4.5 gallons vs. 3.8 for Gen 2), I would not be surprised if GM turned up the injection rate on Gen 2 to further suppress NOX emissions especially given the VW trouble and more scrutiny on staying within limits.


----------



## jrb3 (May 17, 2017)

I put about 2.3 gallons in this weekend (DIC said 34%, iirc). At 4500 miles. I know it was full from the dealership, because I watched them dump some down the side of my car when they were filling it up when I was finally taking delivery.


----------



## IndyDiesel (May 24, 2015)

I would say panjet is correct, I use very little def fluid on a gen 1 diesel.


----------



## NoDanaOnlyZool (Jun 29, 2017)

I did my first DEF tank fill-up today on my 2017 Cruze TD. I have been checking the DEF Level DIC message since about 3000 miles, and saw today that I had 37% remaining at 3228 miles. Since I was driving to a Chevy-Cadillac Dealership for work (as a Cadillac Product Trainer), and I had just over half a tank of Diesel fuel remaining, I figured I'd just buy DEF at the dealership. When I arrived for work, I was at 36% DEF Level and at 3315 miles. I bought a 2.5 Gallon jug of DEF for $16.79 including tax. That was a discounted price, too. Clearly I can save quite a bit by purchasing DEF at a Truck Stop or some other place that does not charge $6.72/Gallon for the stuff. However, since I do what I do for a living, I'll chalk this one up as a learning experience (and a $ win for the dealership team). I help them, and I try to support them whenever I can. That said, their DEF was quite pricey compared to most local truck stops which charge more like $2.80 - $3.00 a gallon. Additionally, I had about a quart remaining when I had filled my car's DEF tank. So next time, I'll probably wait until I refuel the car to top off my DEF tank as well for a lot less per gallon. Though I must add: even at the (much) higher price, DEF only cost me about half a penny per mile thus far. Quite reasonable, in my opinion. DEF and Diesel Fuel costs so far have averaged 4.98 US cents per mile.


----------



## Cruze5pmOT (Jul 26, 2017)

I haven't had to refill in a while and it's worrying me. About 10000 miles ago. Dealer filled it (I know because they left a mess) and car readout still says DEF LEVEL OK. I stuck a clean dowel in the tank and it's 3/4 " up from the bottom . Am I panicking for no reason?


----------



## IndyDiesel (May 24, 2015)

Cruze5pmOT said:


> I haven't had to refill in a while and it's worrying me. About 10000 miles ago. Dealer filled it (I know because they left a mess) and car readout still says DEF LEVEL OK. I stuck a clean dowel in the tank and it's 3/4 " up from the bottom . Am I panicking for no reason?


If you are concerned about it just fill it to the top. I have a gen 1 I am about 10k miles since I last added def and it wasn't full when I added, granted my tank is a little larger. You don't have to wait for a notice to add fluid. Have you already gotten first two free oil changes? Assume they are adding at oil changes?


----------



## Cruzator (Dec 31, 2014)

Same as LiveTrash. My gen 1 will go 12,000+ miles on a tank of DEF (4.9 gallons).


----------



## Cruze5pmOT (Jul 26, 2017)

IndyDiesel said:


> Cruze5pmOT said:
> 
> 
> > I haven't had to refill in a while and it's worrying me. About 10000 miles ago. Dealer filled it (I know because they left a mess) and car readout still says DEF LEVEL OK. I stuck a clean dowel in the tank and it's 3/4 " up from the bottom . Am I panicking for no reason?
> ...


My cruze is a gen 1. I got it certified pre owned so I only got 1 free service. I'm testing to see when it starts to tell me I need to add. But if it kills my exhaust I may be responsible fir repairs.


----------



## Dirk vds (Aug 2, 2017)

Yesterday morning the readout was "DEC okay". Later that day it said about 900 miles left. Car was just over 3000 miles. So I guess at 75 mph 3.8 gallon DEF is good for 4000 miles at that speed.


----------



## Tbud (Aug 20, 2017)

The DEF consumption is also based on the oil you use, because some oil always gets burned and the less ash it generates the less DEF is needed. So, if you use Pennzoil 5W-30 Dexos2 it has a very low ash oil and the DEF would last longer. Other oils people use, and if a shop or dealer uses the wrong oil can cause more DEF consumption. Some diesel technicians will just use the same stuff they put in the trucks probably. Some people use other European formulations for vehicles that may not even use DEF. The Pennzoil is a European formula as well. Any Dexos2 should be low ash, but not all are created equally.


----------



## HondaTech2016 (Apr 20, 2017)

Mine finally dropped to 37% arouns 3700 miles. But i did attempt to put some in around 300 miles because the light came on ( bad injector). I put 1.5 gallons, because thats all i had.i dont really want to buy any more because itll take me awhile to get that many miles again and ive heard that def can go bad once its opened. 35% should be around 2.5 gallons to fill, which is what most places sell it in.


----------



## jrb3 (May 17, 2017)

I can say that mine was full at delivery and with 9,000 miles on it, I have put 5 gallons in it (2.5 gallons each time). So, about 1800 miles per gallon. Not great.


----------



## KyleB (Mar 12, 2017)

That's pretty consistent with mine, at 7k mi, I've added 4.5 gal so far; 2.5 gal myself, and the dealer two more when I got my first oil change.


----------



## obnxous (Jan 17, 2018)

Gen1 here.
Just topped mine off last night. It hit 35%. I found a truck stop with DEF on a pump. $11 for 3.927 Gallons that lasted almost 11k miles. All highway for me.


----------



## firehawk618 (Feb 24, 2013)

Tomko said:


> A couple of things that may help understand this situation:
> 
> 2) The DEF level indicator is programmed by GM to show OK until the level drops to 35%. GM does this on all of its diesels. DEF has a limited shelf life of approximately one year. Once DEF 'goes bad' it will not fully treat the emissions and will set a code eventually preventing the engine from running in any useful way, in accordance with emissions regulations. I suspect that GM uses this OK until 35% level indicator as a strategy to prevent owners from needlessly topping up their DEF and causing a situation where the quality of the entire tank of DEF has deteriorated to a point where it can no longer properly treat the emissions and cause the vehicle to go into limp mode. The analogy I'd make is of someone who never lets their fuel tank drop below 1/2. At best, they're only ever driving around with 1/2 tank worth of fresh fuel, diluted with 1/2 of stale. Repeat that over and over for two or three years and you've got a problem with any perishable product.



**SHRUG** Mine shows from 100% on down to the 50% that it's currently at.


----------



## TheFyreman (Mar 11, 2019)

This is an informative thread! First of all, I had no idea the Gen1's got so much better mileage between DEF top-offs. I came here looking for possible causes of mine being down to 33% after about 2,000 or so miles when, before, I'd gotten about 4-5K between refills. I think I figured out the issue because my 22 yr. old son has been driving the car, and I gleaned from these forums that the DEF usage will be higher when not on the highway. I do almost all highway and my son (who also has a lot heavier foot than I do) does a lot of non-highway and 'in traffic' driving. I'll top it off when it gets down to needing a refill and note the mileage this time.


----------



## MP81 (Jul 20, 2015)

Well, the Gen 1s have a much larger DEF tank than the Gen 2s do.


----------

