Why totally fill the DEF?

Why totally fill the DEF?

During my 10,000 mile services, I opted not to totally fill the DEF. Instead I added one gallon of AdBlue. I then checked fill level with VCDS. It indicated 80.18%. Each half-gallon bottle increased fill level by 9.23%. This indicates about a 5.4 gallon capacity. The owner’s manual says, “about 4 gallons.” If we can assume that the vehicle’s DEF tank was completely full 10,000 miles ago, that calculates to about 2 gallons per 10,000 miles. For future services, I plan to buy Peak BlueDEF from WalMart which comes in a 2.5-gallon container and is much cheaper. I also plan to wait until the tank is nearly empty to minimize carrying the extra weight and have fresher DEF. The vehicle should alert us when there is only about 1500 miles worth left. The VW owner’s manual says any DEF that conforms to ISO 22241-1 is okay. BlueDEF claims to meet this requirement.

Thanks for the info.

Good info.

Mine uses ~1.67 gallons per 10,000 miles, which is coincidentally exactly the same that my '12 Passat used. I drive about 95% highway, so I assume my usage is lower than somebody who does more stopping and starting.

The 2 gals/10k sounds probably about right for the average driving style.

I had my first fill a little while ago. I decided the 2.5 gallon jug was the way to go. Add one of those when the warning light comes on. Cherry pick a bit to see if you can get a sale (which i did last time) since there is some buffer from when the light comes on. I too do not want to carry extra weight, or have older fluid in the tank or sitting in the garage because I overbought.

I top up my windshield washer fluid every time the light comes on.

from vcds, i was at around 29% full and getting 1300 mile warning. i added a box of DEF (2.5gal) from walmart, and it brought me up to 76%. no more adblue warning.

I top my DEF off at the truck stop every oil change. At $3.50 a gallon its no big deal. But if it can go 2 oil changes thats nice to know.

22,500 kms and still no light. 95% highway driving.

Highway driving in PEI? hehehehe that's cute

That seems like one of the places VW listed as not to sell a late model TDI.

Dpf ≠ def....

I think I overfilled my DPF. VW gave me a new one. (Code P0401 after the fix.)

2015 Passat with phase 1 fix just gave low adblue warning this past weekend, just shy of 15K on it from the dealer fill when we bought it last April.

No bad consumption.

Today I am working on my 20,000-mile service. According to VCDS, in the last 11,000 miles, 32.11% of the DEF was used. If we can assume that VW's claim of a 4-gallon tank is correct, that is about 1.28 gallons for 11,000 miles. With this info, I plan to only add one gallon when the low DEF warning is indicated. The vehicle should travel nearly over 8,500 miles until the next warning. This consumption rate may change as I recently had the emissions mod phase II completed.

Since I bought mine--it was at 11800 miles-- I have put 9000 miles and so far I have no warning yet. However, out of curiosity I will check the remaining amount with vcds this weekend.

Reading everybody's posts makes me wonder what's going with my car. It seems to be using DEF a good bit faster than others. Mine was new old stock, bought with under 100 miles on it. I was told all fluids were checked and "topped off" when I bought it. Only thing I verified was oil (which I asked them to change on delivery day while I waited).

I had the warning before my 10,000 mile service. I don't remember the exact mileage but I know it said the car wouldn't start (or something to that affect) before I needed to go in for service. I put in 2.5 gallons but didn't check VCDS. It was then topped off at my service but I don't know how much they put it. I'm somewhere around 15,000 miles now. I will report back when I get the warning again.

How you drive the car also plays into the consumption. Doing a lot of city driving? Our Passat rarely sees a trip with less than 30 miles.

The low DEF warning came on. It said I had 1500 miles left. I was about to pass Walmart so I went in and grabbed one of the 2.5 gallon BlueDEF ($12-13) and poured it in. The tank went from 34.61% to 79.52% filled.

I ponder whether I should left the warning ride for another 1000 miles or just continue to put more in as soon as the warning chimes to avoid the annoyance.

If 2.5 gallons equals the difference between 79.52% and 34.61% (44.91%), This says that the tank holds 5.57 gallons provided that the tank fill sensor is accurate.

Since purchase, I've added a total of 3.5 gallons of DEF. I've put about 26,000 GPS miles on this Golf, about 85% highway. Assuming that the tank was full at purchase, that is 3.5 gallons plus the 1.14 gallons that would be needed to fill the tank to 100% today. So 4.64 gallons to drive 26,000 miles or about 5600 miles per gallon of DEF. This is similar to my previous figures.

Interestingly, I got a 1500 mile warning at 34.91% (1.92 gallons). Based on my calculations, the car should be able to go another 10,000 miles with that amount of DEF. I wonder if the VCDS will reprogram the warning at a lower level.

I'm not measuring via VCDS, but I will say that I'm putting in the Peak 2.5 gallon jugs as the light comes on too. It seems to last 8-10k but like you, I understand why they put the warning on with 1500 miles, but I'd personally rather it be 1000 or 500.

I ran mine down to 400 miles remaining before adding 2.5 gallons. The expected range drops off in increments of 50 miles.

Yesterday I got the DEF low notice at 41350-ish mi on the odo. The dash indicated 1500 mi remaining. Today at 41560 mi, the reducing agent fill level sensor indicated 43 mm. The distance to empty was 1961 km on VCDS and the dash indicated 1300 mi remaining. The reducing agent fill sensor was 33%. The DEF volume sensor indicated 3.61 liters. After adding 2.5 gal DEF (some had leaked): 101.0 mm. 12487.2 km remaining. Volume 12.81 liters.

At around 26,000 miles I received the last “1500 mi left” warning at 34.61% of DEF in tank. I added 2.5 gallons of BlueDEF. So 2.5 gallons lasted 15,350 miles, about 6100 mi per gallon. That's close to the 5600 mi calculation I got previously.

With industry standard DEF consumption being 2% per gallon of diesel, you getting 45 mpg and only using 1 gallon of def per 6100 miles driven, you're still about half the consumption rate.

I wonder how the spot NOx testing is going on these fixed cars, either they are killing it on EGR duty cycle to save a few pennies of DEF or they really dug in on the compromise NOx limits VW and EPA settled for.

I fill mine at every oil change cause I dont wana see warning messages.

2015, Oil change (10k) = AdBlue jug from Walmart. Never get the light but 80% of my miles are highway. I plan to run until I get the light and then fill, as last time when adding AdBlue it couldn't take the entire jug and made a mess.

Too bad we can't give up half of the DEF tank for a couple more gallons of fuel.

bigb said:

Too bad we can't give up half of the DEF tank for a couple more gallons of fuel.

Click to expand...

You can eat your cake and have it too, it's called the Passat, 600-900/tank.

(just don't try putting too much in the trunk, it's runs out of height quite quick)

I added 2.5gallons to out Passat when the light came on at 48K, will prob toss the other 2.5 gal cube I have around 55K or 60K and call it good until 70-75K.

DEF 1500-mile warning on at 55960 mi. Last warning was at 41350 mi so 2.5 gals of DEF lasted 14610 miles this time.

Prior, I just bought a 2.5G jug from Walmart whenever the light came on.

This however has made life super easy. B5 and DEF right at the island. Note that removing the misfuel adapter is needed for the truck pump.

I filled my GSW couple weeks ago after dealer failed to fill it during 60k service. I used the Supertech from Walmart 2.5 gallon jug-shelf said $7.48 but came up $6.98 at register. I used all but a few ounces....

Why not update the title of the thread? (It seems the OP is still around.)

I still quickly read it as "why totally fill the DEF"

Great minds think alike.