So I finally did what I’ve been reminding myself not to do for years - I filled our diesel Audi with unleaded. I noticed within thirty seconds or so that the car was running oddly and managed to get it into a car park within a mile. It’s late on a Sunday afternoon here now, and I’m wondering the extent of the damage I’m likely to have caused. Also interested in how a mechanic may go about fixing this. Is it likely to be a drain and refill, or can I expect a more complex procedure…?
At the least they have to drain the tank.
She won’t start cold on the wrong fuel so after the tank has proper fuel in it, they will probably disconnect the fuel line at the engine and run the fuel pump to flush it with (more) pure diesel.
ETA a quote in the same article that quotes The Dope, so it must be true.
How much fuel was in the tank before you filled it? How new is the car?
Half gas and half diesel will give something like kerosene that. With an old school diesel engine you could probaly just add some 2 stroke engine oil and drive off.
Would not mess around at all with an Audi though. I doubt any serious damage, but God help you if you take it to the dealer.
After doing some research, it seems TDI engines are actually much more tolerant to gasoline than older diesel engines. Makes sense, as they are designed to run on ULSD which is basically kerosene. So there parts do not require as much lubrication.
So again, much depends on how much fuel was in the tank to start with. But as you caught it quick, probably just needs a drain and flush.
I was a mechanic at a VW/Audi dealership until a year or so ago. We saw people do this all the time. Surprisingly VW covered the newer TDI’s under warranty for 1 misfuel per customer. Usually the high pressed pump would get shredded and send metal shavings throughout the fuel system. Under warranty we drained the system, replaced the high pressure pump, low pressure pump, all fuel lines under the hood, fuel injectors, filter, filter housing, and fuel rail. Pretty big job, but free under warranty in many cases.
Audi also covered it back then on that particular engine, but it’s hard to say what they are doing these days, plus you may have a different engine than I’m thinking of. The first thing we did was look at the high pressure pump. There was a small metal cover held down by two T25 torx screws. You pop it off and if you see a bunch of glitter in there, then the fuel system is gonna be toast.
Do you know what kind of engine is in yours?
Here’s an article describing the procedure, I’ve done tons of them before and its pretty accurate. We didn’t change the tank itself tho.
http://humblemechanic.com/2012/05/24/what-happens-when-a-tdi-is-filled-with-gas/
This applies only to the 2.0 TDI
As Fistar has said, It depends on how much gas was put with how much diesel. In the early VW Rabbit diesels, VW allowed 10% gas in the diesel. Early Caterpillar diesels also were allowed a 10% mix. This allowed mix had the added benefit of easier starting in cold climes. More then 10% was not recommended.
What does “running oddly” mean? This is a bad sign. Is the engine making loud banging noises? Is the injector pump squealing shrilly? If either of these is happening, get a quote before proceeding. It may be cheaper to replace the engine &/or the car. Good luck!
As a minimum, the tank needs to be drained, flushed, & refilled. The lines need to be blown out, flushed, & bled. The injectors may need to be bled until all of the gas is out of the system.
The flushed fuel could be used in very low compression engines. Do you have an old rig? A 1948 Willys CJ-2A comes to mind.
Thank you for your prompt responses - what an amazing community.
First up, the good news. It’s covered by insurance. It’s a 2009 Q7 3.0 TDI. It was running towards empty so being a Sunday I thought I’d refuel ready for the week. It’s my partner’s car and to be honest I don’t usually do the refuelling and on this particular occasion my intelligence was off elsewhere. After filling, I travelled a few hundred yards and the car started to jerk both under acceleration and when I took my foot of the pedal - it was then that I figured I had a problem. It was only after I parked that I looked at the receipt from the gas station and realised what had happened. Anyway, it’s being towed to a dealer in the next hour or so (waiting for the call to unlock for the tow truck driver) and after that it will be left to the experts. I’m heartened that (a) I’m not the first person in the history of the automobile that has done this, and (b) that the recency of the engine may work in its favour.
Thanks again for your responses.
I worked for a leasing company that also rented to the public. Several times a year we would get calls that a customer had filled his truck with gasoline. Mostly smaller truck in the 1 ton class. Our compnay policy was to tow truck to dealer and bill customer. I never saw the bills but they were substantial. On occassion we would take pity on a client and have the mechanic just pump the tanks and refill with diesel. As far as I know we never ran into any problems doing that if the truck had not been run too far. If it were only 5 gallons or so we might just put a few qts of oil in the tank.
This is nonsense. diesel engines have been turbo & direct injected for decades before VW/Audi branded it “TDI.” I think what you mean is “common rail” diesel engines.
stripping residual sulfur out of #2 diesel does not make it kerosene. ULSD has to work properly in millions of older diesel engines with mechanical fuel injection, so it still needs lubricity enhancement additive packages to prevent destroying the injection pump/unit injectors. But even so, the high pressure fuel pump (HPFP) in a common-rail engine still relies on the fuel to lubricate the working parts. We’re talking about something which can pressurize the fuel to up to 30,000 PSI, running gasoline (a terrific solvent) through it risks galling the surfaces of the pump internals in short order. now the OP might be saved by the residual diesel fuel in the tank providing enough lubricity to have prevented any damage, but yes the first order of business is to get the tank drained and the fuel system flushed out.
Yeah. VW has brainwashed me with their branding. Common Rail.
As to the fuel, the sulphur is just the canary in the coal mine. The long chain chain hydrocarbons come out with it. Putting it in the same fraction as kerosene.
But as you say, they put loads of lubricating additives back in for older designed engines.
And was just reading how quickly the pumps can shread. Fast.
the funny thing is kerosene still can have up to 3,000 ppm sulfur content…
Yeah, #2 diesel now cleaner than #1… But it is getting cleaned up indirectly by the ULSD regs. So now some kerosene venders are starting to slap an ULS Kerosene sticker on their buckets.
Which I am pretty sure means that it is exactly the same stuff as the ULSD diesel sold at the gas station, except with no lubricating additives to foul up people’s heater wicks.