Petrol in a Diesel Car in Maryfield: How Worried Should You Be?
Provided it has not been started, you can worry far less than you likely are. Until the ignition primes your pump, your starter cranks, or your car is driven, petrol in a diesel tank simply rests there and does nothing. Which means the truthful reply to that first Maryfield query — "have I wrecked it?" — normally no. Leave the engine off then call Petrol in Diesel — that is how you keep it that way. The rest of this page explains what petrol really does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you again.
Inside the motor: what petrol in a diesel does
Two jobs fall to diesel on its route through a motor. It protects first, and only then does it burn. Very fine tolerances go into the fuel injectors and the high-pressure pump, and just your diesel running through keeps those surfaces from grinding together.
Petrol handles the first job poorly and the second not at all. The knocking comes from petrol being designed not to ignite when compressed, which is precisely the opposite of what a diesel needs. On top of that it is runnier than diesel, it strips away the lubrication your system depends on, and any pump working on such a blend is wearing itself.
Taken together, they show the shape the trouble takes. The damage is done by circulation, not by contact. Any tank with petrol in it is a fuel fault. A pump that has been working on that petrol is the start of a mechanical one, and whatever a worn pump sheds moves on with the fuel to the fuel injectors downstream.
How serious is petrol in a diesel? Four situations we see in Maryfield
The best case there can be: filled up, not once started. The petrol is in that tank and only that tank, and the task is a drain and a flush where your car sits. This is the one scenario that can only really happen on a forecourt, since anywhere else the car has been driven to get there.
Started for a second, or just the ignition on. Petrol has left the tank and reached the filter and the lines, because the fuel system has been primed. Normally little more than draining, flushing and seeing to the filter, so still straightforward.
Driven a few miles. Now the pump has spent these miles labouring on diluted fuel. How hard your car was driven matters as much as how far, and this work takes in your tank, the fuel lines, your filter and clean fuel through the entire circuit. Short trips, like the school run to the local primary school, are one matter. Very different again: a trip to Dundee, under 3 miles away, or some miles on the M90, under 25 miles from Maryfield, where your engine never stopped running hard.
It protested, and only then stopped: smoke, knocking, a throttle gone soft, an idle gone lumpy. The fuel isn't acting like diesel any more, and the engine is telling you. Stop where you are — on the verge on Clive Street, at the kerb, down a side road — and don't move it. What comes first is still the fuel drain and flush, and that deals with it, with permanent damage very unusual if a vehicle is pulled over quickly.
Petrol in a diesel myths Maryfield drivers hear
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Nothing is removed when you top up — your tank simply carries more of the same blend. That advice supposes a diesel fuel system tolerates petrol by percentage. It does not.
Myth: "A newer diesel can cope with a bit of petrol." If anything, the reverse. At higher pressure, through smaller components: that's how a modern diesel moves its fuel, so the lubrication counts for more, not less.
"It starts, it drives, and so no harm done" — the myth that trips up most motorists than any other. Any petrol motor fed diesel normally will not run, and so the driver stops and the damage stops with them. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually will; meanwhile your pump grinds. Running is not the same as fine.
Myth: "Add some two-stroke oil and drive it home." It is an old workaround for a separate fault. What petrol has diluted stays diluted, and that petrol stays inside your tank anyway.
Once the motor has been run, part of that petrol is in the fuel filter and your lines, not your tank — and the next start sends it right back through your pump. So the myth "drain the tank yourself and you are sorted" doesn't stand up. It's also genuinely risky to drain petrol into a can by the kerbside.
How petrol ends up: petrol in a diesel
It's seldom carelessness, and nobody does it on purpose. A diesel nozzle generally won't go into a petrol motor, but the smaller petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error straightforward, and just in that direction.
It happens when habit and the car stop matching. Courtesy car, hire car, or a vehicle that's brand new. One petrol and one diesel on the drive of the same household. A familiar forecourt with the pumps in a different order. A train to catch, and a hurried fill en route to Dundee. Years of petrol cars behind you, a diesel Renault Megane in front of you at the forecourt for its first tank — that is when. With rain, a call coming in, or children to deal with, your hand just does what it has always done.
How to avoid petrol in a diesel on your next fill-up in Maryfield
- The label is what counts, so check the petrol pump rather than the colour: in the UK unleaded handles are normally green and diesel black, but not on every forecourt.
- Plenty of cars state the fuel inside your filler flap or on the cap, so check there on the first fill in a vehicle you do not know.
- A coloured fob or a sticker on your diesel's key achieves more than any amount of intending to remember, in a house with one of each.
- Say it before you lift it. On the first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump. It seems daft and it does the trick.
- Mistakes like this are easy to make while your mind is on something else, so the phone goes away.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler built to block a petrol nozzle, and aftermarket devices are available for the remainder. Treat it as a safety net, and keep checking the pump.
- Spotting it mid-fill? Stop at once. A weaker blend results from less petrol inside that tank, yet the next stage stays the same: don't crank it.
Petrol already in a diesel around Maryfield? Start here
Then the order of things is brief. Leave it unstarted, with the ignition switched off as well. Still at the forecourt, at Esso or anywhere else? Ask the attendants to help you roll the car away from the petrol pump. Next, 0333 366 0103. We will ask what got in, about how much, and if it's been run.
Say so if it was AdBlue instead of petrol: it's a different problem, with its own page for Maryfield, since AdBlue brings corrosion and deposits rather than lost lubrication.
Why one petrol in a diesel job in Maryfield costs more than another
The four situations above are four separate tasks, so no single quote for this would be fair. What moves the cost is mostly which of them you're in. Two things come after that: the petrol that was put in as a share of what that tank holds, then the place your car is in and whether a van can reach it safely.
Three queries come first, before any quote, instead of after — what got in, how much, has it run — and that is the reason. A range becomes a straight figure once those answers are in.
About Maryfield, for a moment
Maryfield is a coastal suburban area in Dundee City, situated approximately 1.5 miles from Dundee city centre. Maryfield has a relatively low elevation of 92 metres and is characterised by predominantly flat-type housing. Maryfield is close to nearby places such as Linlathen, Hilltown, and Craigie, and is home to a population of around 5769 people.
Across Dundee City and around Maryfield: fuel drain cover
Petrol in diesel call-outs in Maryfield — part of the DD postcode area — go to vans that likewise cover the places around it, Linlathen, Hilltown and Craigie among them. Our technicians drain where the vehicle is — your own drive, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
Still at the pump around Maryfield?
In that case, you couldn't be in a better place. Switched off it stays; then ring.