Q: I accidentally put diesel in my Mercedes gas tank.

asked by on December 30, 2016

hi, i basically put £25 worth diesel in my car and drove it about 15 minutes without realising, made it home then called the breakdown. they took it to repair on the 23rd dec, 2 days ago they called me to say it will cost me £1000 to fix, but then realised it was diesel in a petrol car. then they called me to tell me they dont know if they have to but it may cost £4000 instead because they may need to change everything. then they ask there technicians to only tell be it would be £1440 in total for change in injectors, new fuel delivery unit, flush tank, fuel line. i then agreed to this amount, however got a call to tell me the car would start they put new plugs in also but nothing, they checked to see maybe there is pressure in the engine but there isnt and engine was good. now i am worried because i feel like they are mugging me off by spending more time on it bare in mind they only flushed the fuel out today. am i being ripped off by mercedes as they only just flushed the diesel

My car has 32000 miles.
My car has a manual transmission.

Fuel Filter Replacement $98.50 - $325.56 Get a Quote

How much damage you did depends on how strong the mixture of diesel was and how far you drove. If the tank was nearly empty you may have messed some stuff up. Getting the car running may not be a big deal. You drain the fuel tank, change the fuel filter and put in fresh gas. If the car then starts and runs, then it is also a good idea to change the oil; certainly not a thousand pounds worth of work. But you will likely have problems down the road. The diesel can damage the non-metallic components of the fuel system and cause them to fail prematurely. So your car may not be very reliable until you’ve had a few failures and changed a few parts. The fuel pump and the injectors and any other component that is exposed to the fuel may fail before it’s time. The quote they gave you was probably to do a comprehensive repair in which they could guarantee you would not break down later on because of this problem. If you like to take your chances, just go with the fuel and filter change and take the problems as they come. But if you are troubled by the idea of breaking down on the road, you should go with the comprehensive repair. If you would like to get another opinion, you can contact Your Mechanic to have a technician come to your home of office to check out your Mercedes and advise you as to what should be done.

Unfortunately, it would be difficult to make an assessment from a distance. In my 30+ years of working on vehicles, I have experienced "misfueled" vehicles that responded to a complete draining and cleaning of the fuel system - fuel lines disconnected and flushed, fuel tank cleaned and reinstalled,etc. I have also experienced others where components like fuel injectors and fuel pumps required replacement. Fuel systems can be temperamental vehicle to vehicle. I had a fuel pump fail in one of my personal vehicles some years back and not even due to misfueling. I replaced the pump and fuel filter as a matter of course. The vehicle started and ran fine. Within 10 minutes of my drive home, the check engine light began flashing and the engine died. Turned out that even with the pump and filter replacement, debris from the failed fuel pump made it forward and lodged 2 fuel injectors wide open. Two cylinders flooded with fuel, causing a bent connecting rod in one of them.

Unfortunately it may wind up being trial and error as to which components respond to a cleaning and which require replacement.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Experienced Mechanic?

Earn up to $70/hr

What others are asking

Key gets stuck in the ignition and is hard to get out
Provided that you can turn your key to the off position where you would normally pull it out, it appears that the tumblers in your key cylinder are sticking or binding, preventing the key from being extracted. A quick simple...
Bad clutch safety switch or starter.
Hello, the only way to diagnose this no start concern is with a DVOM. Power needs to be checked starting at the starter motor, 12v at the big wire going to the starter and 12v at the smaller wire at...
Car won't crank up as well as some other electrical issues
This sounds like a BCM (body control module) malfunction. This could have been caused either by a low voltage issue (https://www.yourmechanic.com/article/how-to-check-the-voltage-of-a-car-battery) or a voltage spike. If the electrical system is dead, there is a power fuse that comes from the...
Brake calipers needing replacement after brake pads and rotors were replaced?
I think you have it backwards. The pads and rotors do not cause bad calipers, but a sticking or binding caliper (https://www.yourmechanic.com/services/brake-caliper-replacement) can cause the pads to wear excessively and cause the pads to dig into the rotors. The calipers...
I hear a creaking noise when I turn the water pump
Hi - If you spin the fan and can hear a noise, that is an indication that the water pump bearing is failing. It would be best to replace the water pump (https://www.yourmechanic.com/services/water-pump-replacement) as soon as possible so it doesn't...
Manifold overheat!! Its (KILLING ME!)
Hello. Thanks for writing in. The vehicle's malfunction with the exhaust system has likely caused the catalytic converter to fail. Unless there is a foreign object in the tail pipe clogging the airflow, it is the catalytic converter which is...
Windshield wipers stopped working. They'll suddenly stop working then suddenly start working again. Has been happening for a week.
The problem you are describing likely stems from an intermittent electrical fault in the wiper circuit. The windshield wiper system uses a small electric motor to move the wiper arms that you see on the windshield. That electric motor is...
The throttle body can be cleaned, however prior to doing that the cause of the loss of power should be diagnosed. In particular, check to see if the OBD-II system has stored any codes that might give clues as to...
1999 mazda 626 has no fuel and no spark
It sounds like you may have an issue related to power getting to both the ignition system and the fuel system. I would suggest checking to make sure there is power running to the ignition module and the fuel pump...

Related articles

What Is E85 Ethanol?
E85 E85 ethanol is a fuel that can be used to power internal-combustion engines. Some vehicles can use E85 and gasoline, while others are tuned for E85 only. E85 is named as such because it is 85% alcohol. The other...
4 Essential Things to Know About Running Out of Gas
While it would be nice if it wasn’t so, every vehicle can run out of gas. The good thing, however, is...
How to Replace a Fuel Filler Neck
The filler neck for the fuel tank fails if there is exterior damage on the neck or if an error code shows that vapors are present.