Skip the auto shop - Our mechanics make house calls

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

asked by on

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.

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.

Was this answer helpful?

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

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

Get a quote

What others are asking

Q: How do I display the current miles per gallon?

There is a message center that is called the Base Message Center. This message center will show you the information about the operations of your vehicle. The Current Miles Per Gallon feature shows your truck's fuel economy in the moment...

Q: New freon, AC groans. Cold only some minutes in morning.

Hi there. What you've described can be caused by multiple AC system components, but I would lean towards the AC clutch cycling switch. The AC clutch cycling switch is a very important component to a modern vehicle’s AC system. It...

Q: Heater blows out cold air

It is very possible that the coolant level in your 2014 Dodge Dart is low. The symptoms you are describing are almost always caused by a low coolant level. Likewise, low coolant level means there is likely a leak somewhere....

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...