Don’t Put DEF in Your Fuel Tank
#1 in the “Do As We Say, Not As We Do” Series
Maybe most of you know this already…. maybe you learned the hard way like we did… DEF, or Diesel Exhaust Fluid, is a substance that should never enter your gas tank – not even $2.01 worth of it. It is meant to be injected into the exhaust stream to help remove harmful emissions from diesel engines.
There is a reason why this is the #1 LESSON in this series. It is by far the most expensive lesson we have learned about RVing thus far. I’m hoping any other errors we make aren’t as costly as this one.
Now, I just want to clarify something. Although I keep saying that this is a mistake that WE made, really I was getting ice cream when the error occurred. It is Greg’s job to put fuel in the tank, and while he’s doing that it’s my job to get ice cream – or maple bacon cinnamon rolls, or chocolate, or – well, you get the idea. I’m not throwing him under the bus; he has taken full responsibility for it… I WILL say, though, that if I were the one in charge of driving and fueling up the truck, I’d most likely have done much more damage to things so far. So, let’s give him a break.
How It Happened (Greg’s Story)
The passenger car pumps were very busy, and the area to maneuver in was tight, so we pulled our diesel truck into the semi truck fueling area. We had done this other times. After waiting for one truck ahead of us to fuel up, we pulled up to the pump.
Jana went in to get her ice cream. The pump had two nozzles. There was a display screen with several choices. As it was designed for semi-trucks, there were choices like ‘refer’ (which is for refrigerated trucks I guess), and other selections. I just wanted to select some diesel fuel for a truck…. So after bopping around the choices and canceling and going back and so forth I thought I finally had the correct selection. By the way, every time the display screen said DEF, I canceled out that. Note that I had no idea at that point what DEF is, I just thought it was some sort of fuel additive that semi trucks use…. So I was ready to fuel up, took the nozzle over to my filler tube and it was too large to fit in it. Now, this was the first time where the nozzle was larger than my filler tube; other times that I went to the truck filling area the nozzle fit in my filler tube. So I looked at the other nozzle and thought, well that’s the one that would fit in my truck. There was no labeling on that nozzle such as “warning, this is not fuel, this is DEF, don’t put this in your fuel tank”. After all, in my uneducated mind, I’m at a fueling pump, so I am thinking everything is fuel. So I grabbed the other nozzle, put it in my filler tube and squeezed. I stopped almost immediately because the nozzle handle didn’t have yellow, which most often is what diesel fuel has, and the nozzle was actually thinner than those that fuel pumps usually have. I only put $2.01 worth in my tank. That’s not a lot, right? So, frustrated with the display screen and nozzle sizes, and given I still had a half a tank of fuel already in there, I decided to pull away from the pump and wait a few hundred feet away for Jana. I turned the engine off.
What is DEF, Anyway?
Diesel Exhaust Fluid is a mixture of synthetic urea and deionized water, meant to be injected into the exhaust system of diesel vehicles. In the exhaust system, it is converted into ammonia to break down the NOx gases into harmless nitrogen and water, reducing harmful emissions. Urea crystals form as the water in the DEF evaporates. The crystals are what can cause severe damage to your fuel system, similar to what a substance like sand would do.
Newer diesel trucks have a separate tank for the DEF. The fuel pump nozzles are too large to put into the DEF filler tube, preventing someone from putting fuel into the DEF tank. However, there is nothing to stop someone from putting the smaller DEF nozzle into the filler tube for the fuel tank.
What Happened Next (Jana’s Story)
Greg started the truck and pulled forward to pick me and my ice cream up. We only made it as far as the gas station exit before the truck stopped running. Our truck and fifth wheel were blocking most of the exit from the station. A kind passerby used a strap to pull us out of the driveway and to the side of the road. We then called our Good Sam roadside assistance number. The representative did some research, and found that because of the work that had to be done, we would need to be towed to a Ford dealership. She explained that the fuel system would have to be cleaned out, fuel injectors, fuel lines and filters replaced. She also warned us that they had another client that did the same thing a week prior, and it cost them $12,000. We had no choice, of course, but to set up the towing and appointment at the dealership, which was 30 miles away.
Our truck and fifth wheel were towed to a campground near the dealership. The tow truck driver waited while we disconnected the fifth wheel from the truck, then took the truck the additional 4.5 miles to the dealership. At least we could camp while the truck was being fixed. We had bicycles, so we rode them into town every day to check on the truck and get a few groceries. We were told it may be a week to get the repairs done, as they had to wait for parts. As you may imagine, out-of-towners are not high priority, and other vehicles took priority over ours. It was also 2020, and it was difficult to get parts during the pandemic.
The Bottom Line
It took 12 days, and $7,200 for the repairs. I guess we were “lucky” that it didn’t cost the estimated $12,000 ! All of this for just $2.01 of DEF that was pumped into the gas tank. We were also lucky that we had Good Sam roadside assistance. The towing was completely free. I can’t imagine what it would have cost to have our truck and fifth wheel towed 30 miles.
What to do if you accidentally put DEF in the fuel tank
• STOP ! Do not start the engine, or the DEF will circulate throughout your entire fuel system, causing damage to all of the components.
• DROP ! Call a towing company (or your roadside assistance representative) and have the vehicle towed to a repair facility. They can drop the fuel tank and flush it out, preventing damage to the rest of the system.
• DON’T ROLL ! No matter what, DO NOT START THE VEHICLE. Even if someone is beeping at you or yelling at you to move it.
Also in this lesson – GET ROADSIDE ASSISTANCE! See our page about RV Roadside assistance.