DEF usage on 2015 Passat

[tikal]

This week I changed the oil and, today, I went to Costco and bought a 2.5 gallon DEF. I filled it to the brim and it took around 1.5 gallons of DEF. I believe last time I changed the oil I also filled up the DEF tank. So 10,000 and the engine used 1.5 gallons of DEF. I was expecting more. What is normal average estimate DEF usage for 50/50 city/hyw driving after 10,000 miles?

 

[Jetta_Pilot]

If I can I buy my DEF at a truckstop at a DEF pump in bulk. Bring your own clean container. Way cheaper than those prepackaged 2.5 gal containers.

 

[oilhammer]

The problem with the bulk DEF is that it often isn't mixed properly... the truckers often find this out the hard way. But it is LESS likely to happen on the big trucks, that hold 15 to 25 gallons.

My observance on CVCA cars is the DEF consumption varies wildly, too much to really have a "normal" amount to give you. I get cars in here that take a gallon, I get others that take three. It really just depends on the type of driving. There is a formula that says for X amount of fuel consumed, you should go through Y amount of DEF. But even that isn't really consistent. And I don't think that even applies for non-DPF SCR diesels (which for now is just off-road equipment).

 

[TomJD]

After 30,000 miles I’ve only added DEF twice. The first time it took 1.25 gallons. The second time it took .5 gallons.

If I remember, I’ll add some this week and report back. I’m right at 30,000 so this is a good test.

I have a 2015 Golf, so the CRUA engine. YMMV.

 

[tikal]

Hello folks, thanks for the updates.

OH, that is a good point you bring up. Last year I attempted to fill up the DEF directly at a Buc-ee's station and it did not work with the 2015 Passat. I was also afraid to make a mess in the trunk.

So for the amount of usage I forsee getting the 2.5 gallon DEF container at Costco is going to work for me long term.

 

[740GLE]

i wait until i see a 1200 miles till empty come on then add 2.5 gallons.

So far i think were at 20-25K for 5 gallons, but over the past year mileage has dramatically fallen off a cliff as the wife only does 15 miles a day for her commute vs 45 she was doing since 2013.

 

[hskrdu]

We have GSWs, so a bit different, but have used just under 2 gal every 20k miles. I have been surprised at how little DEF they use.

When these Mk7s were new to us, I bought some 1L bottles of VW DEF from IDparts for the funnel aspect, but that gets mixed with the box DEF, which has been between $7.50 and $10 for 2.5 gallons, or $3-$4/gal. When I see it at truck stops, the spread seems to have been $2.75 to $4 a gallon over the last 6 years, so having it at home has been convenient, and the price about the same.

 

[Tom in PT]

My '13 used maybe a quart of DEF every 5,000 miles when new and before I tuned it last year, since then even less, hardly any at all. I drive with a very very light foot, 80 percent highway.

FWIW my F-250 6.7 uses one gallon per 1,000 miles; the load seems to not matter, whether towing (14K pounds combined weight), or empty.

 

[senez]

I fill up DEF at every oil change. Never had an issue. I've only seen the refill countdown indicator once in 200k+ miles.

 

[TomJD]

I topped it off my DEF tank today and added a bit more than a gallon and a half.

The car has 30,000 miles so over the life of the car I’ve added roughly 3.5 total gallons. I have no idea how much was in there from the factory though.

 

[x1800MODMY360x]

Mine is a 2013 but when I had the High Side EGR deleted, it ran low of DEF in about 3.6k miles.

Now it's all deleted and never be threaten of No Start ever or waste money on DEF again.

 

[oilhammer]

Tom, I put DEF in your Golf's tank at every service, too. It should be listed on the final copy of the work order.

 

[TomJD]

Tom, I put DEF in your Golf's tank at every service, too. It should be listed on the final copy of the work order.

Well, that explains why I can get away with being so negligent!

 

[AverageAndy]

My stock car gets a 2.5 gallon jug from Costco put in at each oil change (every 10K). I always have some left over and just try to remember to add it a few thousand miles later.

 

[pedroYUL]

I don't know how much mine drinks, I just feed both beasts once in a while. They don't seem overly thirsty.

 

[MB2VW]

I use a wooden dowel on my Passat's def tank, and log the sounding in inches. I know the tank is no linear, due to odd shape, but It's the only way to gauge what is happening.

At 161820 miles I added 2.5 gallons to get me from 2.5" to 5.0"

Today (oil change day), I measured at 170387 miles, I read 3.75 inches.

FWIW....

BTW I am running a Kerma Tune.

 

[oilhammer]

Hehe... wooden dowel... that's the same procedure the official ChryCo/FCA/Stellantis TSB has to use as a special tool to measure the oil leaks from the oil filter housing on the Pentastar V6s, to see how much is "allowable" LMAO.

 

[MB2VW]

I still owe you a visit, when I pass through STL... LOL

 

[Tom in PT]

Dowel's been my SST for dipping the DEF tank for a long time now, glad I am not alone. . .

 

[Tom in PT]

Just for the record, when your dipstick reads 5 inches of DEF in the tank it is basically full. I could only add a few more ounces before it was topped off at the very top. Using roughly one ounce per 1,000 miles with my tuned '13.

 

[moon1234]

I have been tracking DEF usage in my 2015 Passat TDI for the last 100K miles. My AVERAGE is about 18k miles per four gallons, but I have had one fill with 25K miles on four gallons. It really depends how hard the car is driven.

ALL refills have been done at Kwik Trip Diesel island DEF pump. No problems.

The fill sensor in the DEF tank is an ultrasonic type. It reads the percentage left and is accurate to hundredths of point (Very Accurate). If you have OBD Eleven check the Reducing Agent Fill Level under the Engine->Live Data section. You will see the percentage remaining.

I always fill the tank when it says 500 miles left. I put four gallons in at the "truck stop" DEF fill pump. It is the perfect amount and no spills.

 

[JELLOWSUBMARINE]

Using roughly one ounce per 1,000 miles with my tuned '13.

My AVERAGE is about 18k miles per four gallons, but I have had one fill with 25K miles on four gallons.

Wow what a difference a tune makes. Really shows the waste of fuel the dieselgate tune dumps to compensate other emmisions like Nox.

Based off the above @ 128 oz. Per gal...
Tuned = 1oz. Per 1,000 miles
Dieselgate = 42.6 per 1000 miles

42.6 times the load up/wear/abuse/use to the rare earth components. How ever you look at it. You'd think the diesel was a planned obsolescence.

 

[moon1234]

What math are you doing?

128 oz per gallon times four gallons is: 512 ounces

512 ounces/18000 miles = .02844444444 ounces per mile.

.0284444444 * 1000 miles= 28.4 ounces

On the 25K mile loop: 20.48 ounces per 1000 miles.

One ounce per 1000 miles is implausible. There is no way it is properly reducing NOX to 90% or better efficiency with that small amount of DEF usage. I would bet money that if the engine was tested on an analyzer it would NOT pass a NOX test. VW's 2L engines already sip DEF compared to almost all other diesels of comparable engine displacement. Also when comparing DEF usage per engine displacement across larger vehicles, like USA based diesel light and medium duty trucks the VW tune is significantly more frugal. 1% vs 2% DEF gallons per used diesel gallons.

There is also no rare earth anything that is being used up by DEF. It is Urea in Water. You BODY makes urea every day (ever take a piss)? The amount of urea used has no bearing on the consumption of rare earth minerals. Rare earth also does not mean they are in short supply either. Just that those minerals are not easily extracted.

Most urea is made from natural gas. When DEF is heated it decomposes to form Ammonia. The ammonia reacts with the NOX in the presence of a catalyst. The Catalyst is usually a plate or honeycomb like structure that is coated with a reactive material (Zerolite or some metals) that in the presence of ammonia causes nitrogen oxides to break down into nitrogen, water and CO2.

As a diesel oxidation catalyst ages more DEF must be used to reduce the NOX to Nitrogen, Water and CO2. There is a sensor in our cars that determines the amount of SLIP or unused ammonia that goes out the tailpipe. This ratio must be kept low or free ammonia will go out the tailpipe. This is easily "smelled" on some vehicles with poisoned catalysts. Either the owner mis-fueld the vehicle, used low sulpher diesel or an engine oil that contains higher amounts of sulphur or phosphorus components. All of which will coat the catalyst (Poison it) and reduce its ability to convert NOX into Nitrogen, Water and CO2.

A TUNE that simply reduces the amount of DEF used will NOT fully do it's job to reduce NOX. The only way to reduce NOX is to reduce the amount of air or the temp of air that enters the combustion chamber, change the distribution of fuel inside the cylinder (Proposed "ducted" fuel injection) or EGR type recirculation and re-burning of exhaust. SCR is the final step to eliminate any remaining NOX.

There is NO WAY a tune will cut NOX by such a large amount as what was stated above and still be effective in it's job. Also keep in mind that as an DOC ages it WILL consume more DEF to do the same job as there is less functional surface area left to use.

 

[oilhammer]

I don't think anyone tuning the car cares about NOx. I certainly don't. If I owned a diesel with SCR, the very first time that system so much as made a hiccup, it'd be gone. No way I'd put up with something that was going to randomly hold the car's operation ransom because some sensor flaked out somewhere, and that's exactly what we see a lot of at the shop here.

I like it in principle. It allows a diesel engine to do what a diesel engine does best: run super duper lean, which means it can use less fuel. Which means less soot, which means less DPF regens, and since it is a post-combustion NOx reduction strategy instead of a during-combustion one, it also means less EGR. Which means less soot, which means less DPF regens... etc.

But the SYSTEM has been (with all SCR diesels, not just VAG's) riddled with fragile components, many that are expensive, and chronic parts shortages and ridiculous wait times. Now, there certainly have been improvements, but in the case of VAG and others (well, EVERYONE that was selling any diesel passenger cars here, and most of the less-than-8500-GVWR trucks), we here will never know. Because they took them from our showrooms. VAG being the most butt-hurt of all... they took their ball and went home, and a lot of us still wanted to play the game.

 

[moon1234]

I don't think anyone tuning the car cares about NOx. I certainly don't. If I owned a diesel with SCR, the very first time that system so much as made a hiccup, it'd be gone. No way I'd put up with something that was going to randomly hold the car's operation ransom because some sensor flaked out somewhere, and that's exactly what we see a lot of at the shop here.

I like it in principle. It allows a diesel engine to do what a diesel engine does best: run super duper lean, which means it can use less fuel. Which means less soot, which means less DPF regens, and since it is a post-combustion NOx reduction strategy instead of a during-combustion one, it also means less EGR. Which means less soot, which means less DPF regens... etc.

But the SYSTEM has been (with all SCR diesels, not just VAG's) riddled with fragile components, many that are expensive, and chronic parts shortages and ridiculous wait times. Now, there certainly have been improvements, but in the case of VAG and others (well, EVERYONE that was selling any diesel passenger cars here, and most of the less-than-8500-GVWR trucks), we here will never know. Because they took them from our showrooms. VAG being the most butt-hurt of all... they took their ball and went home, and a lot of us still wanted to play the game.

I agree. The poster I was responding to implied that a tune, I assume kerma, which leaves all emissions intact would be experiencing multiple orders of magnitude in reduction of DEF use and still be properly reducing NOX emissions by 90% or greater (the requirement) was improbable.

I would not have bothered to respond if the “tune” involved removing emissions equipment. Obviously there is zero NOX reduction in that scenario.