Advertisement

Adding Urea To Clean Diesel Cars: Can I Just Pee In The Tank?

Follow John

Bluetec logo (Dodge Ram HD)

Bluetec logo (Dodge Ram HD)

Enlarge Photo

We get punchy around High Gear Media occasionally, and sometimes we BS back and forth about topics less salubrious than, say, fuel efficiency and lowering our oil dependency.

Which is how the following question came up: If the urea runs low in my new clean-diesel car, can I just pee in the tank to top it up?

2009 Mercedes-Benz GL Class 3.0L BlueTec

2009 Mercedes-Benz GL Class 3.0L BlueTec

Enlarge Photo

2009 Mercedes-Benz ML320 BlueTEC Preview

2009 Mercedes-Benz ML320 BlueTEC Preview

Enlarge Photo

2009 Mercedes Benz R Class 3.0L BlueTec

2009 Mercedes Benz R Class 3.0L BlueTec

Enlarge Photo

The scheme will see consumers given a $4,500 'Eco Credit' towards the purchase of a new 335d or an X5 xDrive35d

The scheme will see consumers given a $4,500 'Eco Credit' towards the purchase of a new 335d or an X5 xDrive35d

Enlarge Photo

The American and Japanese competition face delays as the Germans have the segment to themselves

The American and Japanese competition face delays as the Germans have the segment to themselves

Enlarge Photo

diesel and AdBlue fillers in Audi Q7 TDI

diesel and AdBlue fillers in Audi Q7 TDI

Enlarge Photo

VW, Audi and BMW to offer BLUETEC diesels in US

VW, Audi and BMW to offer BLUETEC diesels in US

Enlarge Photo

Urea to cut NOx

First, a bit of background. Many modern clean diesels, including those using the Mercedes-Benz Bluetec system, inject a liquid urea solution--known as AdBlue--into the exhaust gas to reduces nitrous oxide (NOx) emissions.

Blended into hot exhaust gas, the urea releases ammonia, which provides the right chemistry to let a final catalytic converter convert NOx in the exhaust stream into nitrogen and water.

Bluetec diesels with urea injection emit up to 80 percent less NOx than previous versions, letting them meet new, lower U.S. limits on vehicle NOx emissions--the world's most stringent.

Mercedes-Benz fits the system to its 2010 ML320 Bluetec, GL320 Bluetec, and R320 Bluetec models. BMW and Audi also use urea injection in their clean diesels too, under different names, including TDI.

Refill every 10,000 miles

A urea tank contains roughly 8 gallons, which is enough for roughly 12,000 miles of standard operation. That dovetails neatly with standard 10,000-mile servicing intervals, so Mercedes-Benz dealerships routinely refill reservoirs at every maintenance.

That also meets an EPA requirement that emissions control systems require no owner intervention for at least 8 years or 100,000 miles. Mercedes-Benz programs its Bluetec cars to warn the driver if the tank is running low, to encourage an immediate service visit.

If the tank reaches one gallon, the car notifies the driver. It does so again with only 20 starts remaining. To reset the system, at least two gallons of AdBlue--or four half-gallon bottles, at $7.75 each--must be added. Roadside assistance plans cover AdBlue, however.

Human supplies?

Cost-conscious consumers may want to save money on the refills, which are not covered by the Mercedes-Benz warranty. (BMW's four years of free maintenance, however, covers disposable items--including AdBlue--at no additional cost.)

Consumer Reports was charged a whopping $317 by a local dealer to put 7.5 gallons of AdBlue in its Mercedes-Benz GL320 test car, at $32/gallon for the fluid. Most dealers use bulk AdBlue supplies (though even 7.5 gallons would only cost $116.25 in half-gallon bottles).

And what if the driver is way out in the middle of nowhere, far from the nearest dealer? Can he or she, ummmm, provide some temporary urea to get the car to a dealer? The question comes up simply because human urine contains 2 to 4 percent urea.

But sadly, the answer is "no". A modern clean diesel car will recognize that your pee is not the right stuff.

The wrong stuff

AdBlue solution has a far higher concentration of urea--32.5%--mixed into deionized water.  That's eight to 16 times the strength of your own urine, which also brings with it various salts, toxins, bile pigments, hormones, and roughly 95 percent water.

Sensors in the urea tank monitor the concentration of urea.  If you put in the wrong stuff, from pure water to windshield washer fluid to human urine, the car won't run.

Drat. There goes our consumer tip for the week.

Just twice a year

You may have noticed, by the way, that this is our second urine-themed article within a year. We wrote last July about the possibility that urea could rescue hydrogen-fuel-cell cars because it takes less energy to derive hydrogen from it than from water or natural gas.

That article ended up as our fourth most popular piece of the year. But rest assured, urine does not occur regularly on this site. We have a hard and fast limit of two urine-themed articles a year.

Unless, of course, it's newsworthy.

[Automotive News (subscription required) via Jalopnik, Consumer Reports, Motor Trend, PickupTrucks.com]

Advertisement
 
Follow Us

 

Have an opinion?

  • Posting indicates you have read this site's Privacy Policy and Terms of Use
  • Notify me when there are more comments
Comments (7)
  1. You might want to check out a garden-supply store. Lots of urea-based fertilizers.
     
    Post Reply
    +1
    Bad stuff?

  2. So you didn't answer the obvious question: how do I octuple the urea percentage in my pee so I can use it in my car?
     
    Post Reply
    Vote
    Bad stuff?

  3. John, I had a Datsun when the Block cracked at 100K so I used the tried and true fix for all cooling water leaks – go to the grocery store and buy a can of black pepper and pour it in the radiator – works great even for a cracked block. That little truck – I worked her ass off hauling stuff and she still made it to 180K before I gave it to the neighbors and they used the bed as a trailer and the engine and Tranny for stationary power, totally cannibalized the thing and it would not surprise me if it is still running.
    Late one Friday night on the way to Maine, I was driving the back roads and just had a six-pack on the seat and I was nursing it along and taking a drive. When I noticed the temp gauge blow, so I pulled over and sure enough - steam, so I waited and when she had cooled I popped the cap. I used to carry some pre-mixed radiator fluid in the bed, but that was all frozen so I said “dam” miles from anywhere on some back road in the middle of winter. So I thought what the hell, stood on the bumper took a nice long leak into the radiator, sealed her up and made it nice and easy into the next town, where I found an all night place and picked up some fluid.
    Worked great! My noble Datsun… oh what a sweet gal “ you could piss on her and she would run even better”. Try that with a Mercedes!
    John
     
    Post Reply
    Vote
    Bad stuff?

  4. Now that almost all diesel trucks Class 6-8 also require Urea (aka DEF), try shopping at a truck stop for your refills.
     
    Post Reply
    Vote
    Bad stuff?

  5. yes, but then the next question would be; how can i filter my urine to achieve this urea concentration? what would it cost? i like the idea of the car having a filter that accepts my urine...
     
    Post Reply
    Vote
    Bad stuff?

  6. Even WalMart currently sells DEF in bulk. Can't remember the price on it but I know they have it. I've heard so many people make that comment to me when talking about SCR systems. There is also the rumor that it kills the usability and power of diesels I personally can't really see how it would affect the engine...
     
    Post Reply
    Vote
    Bad stuff?

     
  7. They tune the engines so they can't haul worth a dang, because when a diesel engine is really floored, it makes some smoke.
     
    Post Reply
    Vote
    Bad stuff?

 

Have an opinion? Join the conversation!

Advertisement
Advertisement

Find Green Cars

Go!

Advertisement

 
© 2014 Green Car Reports. All Rights Reserved. Green Car Reports is published by High Gear Media. Send us feedback. Stock photography by izmo, Inc.