What Happens When a TDI Is Filled With GAS!

Published on May 24, 2012 under Humble Mechanic

It is no secret that VW has a huge share of the diesel market for passenger cars. As we push for better and better fuel mileage, I have seen TDIs become much more common. It is not just “those diesel people” anymore. With the expanded range of customers that are now in our TDIs, we see issues that we never seen before.

The TDI that was in the 2002 Jetta was a GREAT engine. We refer to is as the “ALH”. That is the code that VW uses to identify that engine. If a customer were to mis-fuel that engine the repair was simple.

  1. Pump out the gas(it’s a diesel remember)
  2. Change the fuel filter
  3. Add fresh diesel fuel
  4. purge and gas left
  5. Drive home happy

I have only seen 1 “ALH” that was mis-fueled. BTW, if this happens to you, and there is damage, don’t blame me. Just Sayin

Enter the next generation TDIs. Here is where we get more customers buying diesels. Now we have the average driver buying TDIs, not just the TDI folks that usually are INSANE about their cars. I use the word insane in a positive way. ๐Ÿ˜‰

This is when I started to see more and more cars that were filled with GAS, instead of diesel. The Pumpe Duse engine was still mostly forgiving when it came to mis-fuel. The car would just stop running. The repair was very similar to the “ALH”, just something we did more often.

In 2009 we got the “Common Rail”. A highly advanced very complicated TDI setup. The high power, and great fuel mileage were a huge draw. Especially since we had just seen gas prices over $4 for the first time ever. With improved sales came more mis-fuel issues. Unlike the last two generations, this TDI is not forgiving what so ever. When someone puts gas in the Common Rail (CR for short), all that is takes is cranking the engine to do damage.

If the car is started, usually it will be driven until it stops running. What that means is gas is in the entire fuel system. Due to diesel and gas having totally different lubrication properties, this makes the fuel pumps fussy. They start doing bad things like coming apart on the inside, and spraying metal throughout the fuel system. The resulting repair is fuel system replacement. Every part that fuel touches gets replaced, from fuel take to fuel injector! This repair costs about $7800 for parts and labor. OUCH!


Not really a fun time for anyone is it? This is one of the reasons that I am not ALL IN on diesel. I don’t trust myself to properly fill the car. I love the technology, but you MUST be the right person for it.

It does bring up a really good question. Is this the fault of VW, the customer, or the company that made the parts? Yes if you put gas in your car it’s YOUR fault. BUT, shouldn’t the parts be designed with some type of fail safe? Should the fill neck be different so you CAN’T mis-fuel?

~To prevent anyone from ever mis-fueling a car again, just share this post.(ok, that wont happen, but it might be a ‘Humble’ reminder ๐Ÿ˜‰

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  1. Jerry

    A great article!
    In Europe, (where diesel has been prevalent since the late 70s), the Diesel and Gas pumps are not only a different colour, but a different size.
    Although primarily to avoid putting Diesel in a gas car, (the Diesel nozzle is larger and does not fit in a gas, gas tank neck) it also helps remind you if you try and put gas in a diesel car. (the smaller nozzle rattles around in the large neck of the diesel, gas tank)
    So, the Automaker and the Gas Companies have worked out a solution, and of course the drivers have been used to the difference in sizes and colours for way longer than in the US, so it rarely happens in Europe anymore.
    North America is finally waking up to the benefits of diesels, we hope they have learned from Europe; solutions can be found, implemented and used cooperatively. In the meantime, we at Capilano VW supply decals that fit inside the gas flap for that last reminder that it’s a TDI, DIESEL ONLY!

  2. Brandon

    This is one thing I’m scared about for the TDI. I’m considering one, and I don’t think I’ll have to worry about Mis-Fueling, but the people AROUND me. If I loaned my car to my mom or a friend for some reason and they forgot to use diesel because they used gas all their life, i would have a heart attack receiving that call that my car is on the side of the road ON FIRE!

  3. Garrett Craven

    Im just blown away at how tremendous the repair is for the newer TDI’s! Why are they so sensative now when the older models were much more forgiving?! I just dont get it lol also what bothers me is vw more than likely saw the rise in mis-fueling TDI’s but yet made a much much more sensative model.

  4. Garrett Craven

    People are always gonna be stupid lol or at least make mistakes so why they didnt implement some sort of fail safe feature just makes me think they fore saw the issue and looked forward to the spike in repairs and parts sales cuz i highly doubt the warranty covers “oops”.

    1. Charles

      As far as design, I think it has to do with creating such a high power and clean running engine. That requires really high fuel pressure.

      I probably should not say this, but VW covered this repair. ๐Ÿ˜‰

  5. Kristin

    Yeah with all the technology we have now there has got to be a way to put some sort of sensor in so that if regular gas is in the gas tank it does not ruin the whole fuel system. Come on VW ๐Ÿ™‚ Seriously though if I knew it would cost me more than I have paid for any car in my life to fix my car if I put gas in it I would do anything I could to remind myself it needed diesel like stickers in the car on the gas cap whatever it took.

      1. Brandon

        That would work untill a determined blonde still tries cramming the round gas one into the triangle, and ends up holding it over the hole while fueling ๐Ÿ™‚ hahahahahaha

  6. Jessica

    I just recently purchased my first ever diesel and can say after the first fill-up I’ve never accidentally forgetten. I guess this may be because I’m always searching for particular gas stations now, (Shell,Texaco) which I know are likely to have diesel fuel.
    One other thing I have noticed is how few green colored handles there are and how greedy people are when the gas station is busy. I’ve been patiently waiting to get to a green handle pump coming from the other direction than most cars (German car’s fuel cap is on the passenger side, unlike most Japanese and American models which is on the drivers side) and they just scoot on in there and take the pump. So now, I back up into the pump so the regular gas filler can’t shimmy in there before me when the other customer drives off. People probably wonder what the ‘crazy girl in the Volkswagen’ is doing, but I’m gonna get my gas even if I have to go to extreme measures.
    Great blog as always! Excited to see the Cabriolet video tomorrow!

  7. Garrett Craven

    @ brandon…thats hilarious! ๐Ÿ˜€

    @ jessica…you do what you gotta do girl! ๐Ÿ™‚ the benefit to me not having a brand new car…..most people will stop or move when you show no fear of scratching/denting your car! Dont get me wrong i dont wanna…but a good poker face never fails! Haha

    1. Charles

      We had a transport driver fill a new golf with diesel. The car only had 30 miles on it. Luckily he never started it. I was able to repair the car. Bad news!

      @Chris, How many gallons of gas was in that F350. I would guess that it has a big tank.

  8. Doug

    BP has green handles on a third of their unleaded gas pumps! Without considering it wasn’t diesel, I topped off my tdi Passat with 8 gallons of unleaded, drove 225 miles, stopped back to top it off on the way home and realized my mistake before pumping in more unleaded. Drove another 15 miles and topped off the tank with diesel for the final 60 miles home. Hope the engine isn’t ruined. Thanks BP for the green handle!

      1. Charles

        @cbarnes and @doug
        There is a BP by my work. The diesel pumps are black and the gas pumps are green. I can totally see how someone would do that. I stress about it when I put fuel in cars.

        the engine is not ruined, but possible damage to the fuel system. It depends on the engine. CD(newer tdi) can handle little/no gas. If you have a PD(pumpe duse) then you will most likely be fine. Just pump out the fuel, replace the filter and you should be good to go.

        1. Steve

          I just accidentally did this to my girlfriends car – a 2009 VW Jetta TDI (which I’m rarely behind the wheel of). I had filled up 5-6 gallons and drove maybe ten miles before the car just puttered out and died on me. I thought it was the battery at first, and returned to give it a jump the next morning. It started, and I moved it a block to a safer parking spot.

          From there, I turned it over one more time to double-check how it was starting (still thinking it as something with the battery). We checked the battery and alternator, which were just fine, but then realized the car was idling really hard. Then it hit me, and I remembered being in a rush and accidentally fueling up with Unleaded.

          I called AAA and got it towed to my go-to VW mechanic. I won’t know the extent of the damage until Monday when they can look at it. The tow truck driver made me feel hopeful because the car was still firing up and such, and I’m hoping the fuel lines just need to be drained, replace the fuel filter, and flush it with fresh diesel.

          It definitely didn’t blow up.. Any thoughts on how bad the damage is?

          1. Charles

            It mostly depends on if there is metal in the HPFP or not. IF there is, you are looking at replacing a fuel system. If not, you might be okay with a drain/flush/fill and replacement of the fuel filter.

            If there is metal in the High Pressure Fuel Pump, give VWofA a call and see if they can help you out at all.

  9. Todd

    Guilty! This just happened to me today. Now I am researching the issue and found this blog. In a hurry, put about 9 gallons of unleaded into my 2006 VW Jetta TDI. Drove about 70 miles. Got into the city and it died at an intersection. Car currently at shop and mechanic says he hears metal against metal. Does this sound like more damage than just the fuel system? The car runs, but no power and the metal-to-metal sound. Visiting with the mechanic next week. Loved this car and the solid high gas mileage. Hoping damage is just limited to the fuel system. Any comments would be appreciated.

    1. Charles

      What a bummer. Before I replaced ANY parts, I would get ride of the gas, replace the fuel filter, and flush all the lines with clean fresh diesel.

      I have not seen any failures of a PD due to misfueling. I have seen several misfueled, and I was able to drain/flush and replace the filter. That has fixed every one.

      Please keep us posted on what happened.

  10. Tony

    Hi Todd,
    I feel your pain, but don’t dispair… We have a 2003 Jetta TDI and 6 years ago my wife filled the empty tank with unleaded and drove home– around 70 miles as well– before noticing weird sounds and performance only to realize what she had done. I had it towed to our mechanic who did exactly what Charles suggested and that was all that was required to fix it. We were initially very nervous about potential damage and considered selling the car immediately after it happened, but 60k miles later, the car is still perfectly fine. Whew!

  11. Steve

    I have a 2010 Golfi TDI and I accidentlally put 6 Liters of unleaded in my car yesterday to get to the military installation here in Germany and drove about 15 miles (the car was on emptyat the time). I realized what had happened when it started hesitating on the highway and got to the next gas station and filled the car with diesel. The car would not start so I called the german version of AAA. In the meantime, I tried to start it again (worked with diesel engines in the Army) and it finally started. I call the local german dealership and they said to have it towed. I got to the dealer and they said that it could be as little as 600 Euro or up to 7000 Euro. I have two mechanics (friends of the family) here (not VW dealership) and one said that since it was so little, to just drive it unless the warning lights come on or it acts up. The other said the fuels filter and pump must be replaced and the gas drined, etc, but not a 7000 Euro bill.
    Any thoughts on this from an experienced diesel mechanic? I am planning on having it towed about 26 miles back to Frankfurt for one one of my father-in-law’s friends to work on it. The other option is to go get it and drive it home and hope that no warning light come on because the damage is already done. Again, there were no warning lights and it has started after I put a full tank of diesel back in it.

    Please give me some impartial advise.

    1. Charles

      Hey Steve
      The estimate if 600-7000 is spot on.

      I would tow if where you can get it worked on. Pump all the gas out, flush it with good clean diesel fuel ad see what happens

      This would be an attempt to salvage the fuel system. Every time I have seen a newer TDI driven on gas until it shuts off, it has needed the fuel system replaced.

      It only takes a small amount of gas to dry out, then destroy, the high pressure pump.

      Before I did anything, I would give VW a call and see if they are offering assistant with repairs. Here in the USA, VWofA has been paying for most of them.

      Good luck man, keep us all posted on what happens.

  12. Melinda

    My husband filled our rental car in France with unleaded gas. Thre were no indications on the car or in the manual as to which fuel to use. We only discovered the potential pb. As we continued to drive about 60 miles to drop off the car at the agency and the engine was doing wierd things. We have been informed of the situation and that we will be charged. After reading these blogs, it looks like the sky is the limit on the costs.
    Any suggestions?

    1. Charles

      You have to bring it to the dealer. There are parts that must be “released” by VW.

      I have only had 1 time that VW didn’t pay for the repair. I can’t guarantee that for you but the odds are good. Feel free to email me Sherrie. Charles at humblemechanic dot com

      1. lisaryan

        I just filled my 2010 jetty TDI unleaded gas on accident today. It’s been towed to a shop and I’m waiting for estimate. I drove 1 mile before it started to sputter and I pulled right off and shut it off. What do you experienced TDI mechanics think my chances are of a lower cost repair. I bought my Jetta two years ago used and it is no longer under warranty. How do I get VW dealership to cover repair costs? Why are they willing to do this? Thanks for any info!

  13. Gnollo

    Wife put ยฃ20 of gas in the tank, then drove the Touareg (2011) home (1 mile). It was rattling by the time she arrived.
    Had the engine emptied of fuel and cleaned, diesel back in and it sounds fine.
    How do I know if there is lasting damage?

  14. Tony Bruton

    Can anyone tell me – is the high pressure fuel pump in my Golf TDI activated when the ignition is switched on ? My car was misfueled and has not been started but the ignition has been on while it was being pushed off the garage forecourt

  15. Hugh

    Hi Charles, Thanks for your article & for the contribution of others. My wife accidently put a tank full of petrol in our daughters 2006 VW Polo 1.9 TDI Diesel yesterday & drove it until it stopped (about 15 miles). She didn’t realise her error & tried to re-start it but it wouldn’t start, which worries me a little since most of the comments suggest it should have re-started. It’s been towed to the mechanic, I’ll pass on your suggest first response, flush, filter etc. & keep my fingers crossed. Kind regards, Hugh

  16. Whitney

    Charles, I notice this is an old thread and REALLY hoping you’re still active. I did what everyone else seems to have done… filled up an empty 2006 Jetta TDI tank with gasoline, drive 1/8th of a mile before the car turned off. Had it towed home and am horrified thinking about the potential damage. What I do can you offer me about the VW assistance program? Info on how to research this?

    1. Charles

      So your car is a little older than the ones on buy back or that had assistance. Most of that has stopped btw.

      For you, drain any fuel out. flush the fuel lines to be sure there is no gas. replace the fuel filter. You may have to bleed the fuel system out a little to get any remaining gas out.

      Odds are it did no damage. ๐Ÿ™‚

  17. Michael

    I have a 2010 Jetta TDI that I bought new in December 2010. June 6, 2018, just 2 weeks ago, our car stalled coming to an intersection. It wouldnโ€™t start again. Towed to dealership where they found metal in the fuel. Theyโ€™re claiming the fuel failed the contamination test, and wonโ€™t cover it under the warranty we have for the fuel system. Iโ€™m so peeved… even have the last 3 receipts showing I used diesel fuel. (Also Iโ€™m not an idiot and have never mis-fueled my vehicle – I bought it BECAUSE of the diesel). How many miles would you estimate you could go on contaminated fuel before it dies? I was at 384 miles on that tank (im estimating I went through about 8.5 gallons).

  18. Eric

    What about bio diesel in the 2014 Bettle TDI. This fuel has basically shut down my daughters car. Daughter put this fuel in her car thinking it was regular diesel. Not labeled well at the gas station and VW says it is in the owners manual. Thought on what needs to happen to fix properly. Car is under warranty but they donโ€™t wants honor any part of fixing the car.

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