Put Petrol in a Diesel Mercedes B-Class by Mistake?
The motor is safest left off when it has not been started since you put petrol in a diesel Mercedes B-Class, and that covers moving it away from the pump. The petrol cannot get out of the tank while your motor is off, so the B-Class can usually be set right with a fuel drain.
There is no reason to shift your Mercedes B-Class off the forecourt, or from any other place where it stopped, as this drain is done by Petrol in Diesel where your car stands. We'll go through it with you on the phone, so ring us before attempting anything on your own.
Petrol in a diesel B-Class: what to do first
- Don't turn on the engine, even though a diesel B-Class will usually run with petrol in your tank. It can seem normal for a time, and that's how motorists commonly pull away without realising anything is wrong.
- Fuel can be pulled to the fuel injectors even before your engine has fired, since on many diesel engines the ignition alone primes the fuel pump. Keep your ignition off too.
- Topping up with diesel to dilute it is a bad idea, even with super unleaded, which is petrol too. The fuel tank on the B-Class takes up to 54 litres, and every litre of diesel put in is more contaminated fuel for us to drain.
- Forecourt staff will generally help push your car clear in neutral when it's in the way of a pump.
- Once you call 0333 366 0103, we want to know which B-Class you drive, where it is, how much petrol you reckon was put in and whether your engine has been started. The exact version helps too if it is on the badging, for example the B 180 CDI.
Wrong fuel in your Mercedes B-Class after your engine has been started
Wrong fuel in your Mercedes B-Class only begins to affect the engine once it's pulled out of the tank, which is exactly what starting your motor does. Whilst it flows through, diesel fuel leaves your high-pressure pump and your injectors oiled, and the motor depends on that. Driving any distance on that mixture is what can do damage, because petrol thins your diesel and washes that lubrication away.
If you have already driven your B-Class, pull over where it is safe and switch off. We empty your tank, then rinse the pipes and fuel filter through until no tainted fuel is left, so it can still be put right. Very few cars that are caught soon and cleaned out thoroughly end up with lasting harm.
The B 160 CDI is no different in this from any other variant of the B-Class.
Your Mercedes B-Class fuel tank capacity, version by version
What matters is what share of the fuel in your tank is petrol. The same couple of litres count for more if you fuelled up with the tank almost empty, which is why its capacity makes a difference.
Tank capacities on the Mercedes B-Class range from 50 to 54 litres according to the version.
In our data the B 200 CDI has the largest tank and the B 220 CDI has the smallest.
| Version | Fuel tank |
|---|---|
| Mercedes B 160 CDI | 50 litres |
| Mercedes B 180 CDI | 54 litres |
| Mercedes B 200 CDI | 54 litres |
| Mercedes B 220 CDI | 50 litres |
What diesel variant of the B-Class do you drive?
Look for the badging on your boot lid, which usually gives the variant, then tell us what it says when you phone.
Diesel versions of the B-Class have been badged CDI.
AdBlue in a diesel Mercedes B-Class by mistake
Water and urea go into AdBlue, which some diesel cars use to clean up the exhaust. It is stored in a tank of its own, with a separate filler. Even to shift the car, don't touch your key when you have AdBlue in a diesel Mercedes B-Class after it went in the incorrect filler.
Since it is mainly water, AdBlue doesn't burn and gives the fuel pump no protection whatsoever. It does not mix with diesel either, so it drops to the bottom of your tank where the pump picks up its fuel, and a tank holding up to 54 litres does nothing to dilute it the way it would dilute petrol.
No matter how modest the quantity, some of it gets pulled into the line. Deposits of urea build up in your filter, your injectors and the rest of the fuel system once the water dries off, and they corrode the metalwork they touch.
On many motors the AdBlue filler is next to the diesel filler under the same cover, and if the B-Class has one, it may well be there as well. The nozzle for AdBlue is much smaller than the diesel one, and the filler cap is usually blue.
Fuel drain on your Mercedes B-Class: how we do it
A fuel drain on your Mercedes B-Class is carried out beside your vehicle, and it doesn't need to go to a garage. To begin with we check what was put in and whether your engine has been run. Your tank, which holds up to 54 litres on the B-Class, is then drained, the lines and filter are flushed, and your car is filled up with clean diesel and primed before we start the car.
By the end, your B-Class is running on fresh diesel again and all set for you to take away.
What AdBlue removal from a diesel Mercedes B-Class means
We take the same stages for AdBlue removal from a diesel Mercedes B-Class as we do for draining petrol. As AdBlue does not blend in but collects at the bottom of the tank, running the B-Class on it can form crystals in the pipes. Those get cleared through as well, and your fuel filter is changed if it needs it.
What we call AdBlue removal is emptying AdBlue from your diesel tank after a slip at the filler, not taking out or switching off the AdBlue system on a car.
A fuel drain on the Mercedes B-Class: the cost
A fixed quote is not something we publish, since no two jobs involve the same work. It largely comes down to the following:
- whether anyone has started or driven the B-Class, the thing that counts most
- the quantity put in, weighed against the capacity of your tank
- which of the two it was, petrol or AdBlue
- the position of the B-Class and how easily we can get to it with the van
With those details over the phone, we can tell you what the job is going to involve.
Petrol in a diesel Mercedes B-Class: your questions
The Mercedes B-Class fuel tank capacity: how many litres?
It depends on the variant, from 50 to 54 litres, and every one is shown in the table above.
Can I top up with diesel if I only put a little petrol in my B-Class?
It isn't something we'd advise, since putting in diesel does nothing to remove the petrol. It just reduces its share, and the petrol is still in the fuel system after you drive off. Draining takes all of it out, and with a small quantity that's generally all the B-Class requires.
Is a trip to the Mercedes dealer needed for my B-Class?
There is no need to take it anywhere. We drain and clean your B-Class where it has stopped, and we're independent, with no link to Mercedes or its dealers.
Which B-Class I have: does it make a difference?
It is useful for us to know which one you have when you phone, since we hold data for 4 diesel versions of the B-Class.
Does my insurance policy cover wrong fuel in my Mercedes B-Class?
Misfuelling cover comes with some policies and not others, so look at yours. We will come out to drain it for you whether it does or not.
What if I put diesel in the AdBlue tank of my B-Class?
Do not put your key in your ignition in that case either. The majority of vehicles show a warning and go into limp mode if they're driven like that, and the AdBlue system will need emptying. Let us know which tank your fuel went into when you phone.
Already driven my B-Class: what now?
Stop where it's safe and turn your engine off, then keep it off until we arrive. Where you have stopped, the fuel system is emptied and cleaned there, and caught soon like this, it very seldom leaves permanent damage.