Should You Worry? Petrol in a Diesel Car in Mayfield
Unstarted? Then less worried than you probably are. Everyone in Mayfield begins with "have I ruined it?", and the honest answer is generally no: petrol resting inside your tank of any diesel remains harmless till priming, cranking or driving draws it into the fuel system. Leave your engine off then phone Petrol in Diesel — that is how you keep it like that. The rest of this page explains what petrol actually does to a diesel, how to tell how far it has got, and how to make sure it does not happen to you again.
Petrol in a diesel: what does it do to the engine?
Passing through a motor, diesel does two things at once. Before it combusts, it protects — and then it burns. Very fine tolerances are built into the fuel injectors and the high-pressure fuel pump, and just your diesel running through stops those surfaces grinding together.
The second task petrol does not do at all, and the first it does poorly. It's runnier than diesel and takes away the protection the fuel system depends on, so a pump running on a petrol blend is a pump wearing itself. And petrol is designed to resist igniting under compression, which is the opposite of what a diesel needs from its fuel. That is where the knocking comes from.
Put those together and the shape of the problem is clear. Contact doesn't do the harm — movement does. Petrol in the tank is a fuel issue. After the pump has been running on that petrol, a mechanical fault has begun: anything shed by a pump that's wearing down travels onward to the fuel injectors with the fuel.
Four situations our technicians see in Mayfield: how bad is petrol in a diesel?
Filled up, never started. The best case there is. Being at a forecourt is what makes this the case: elsewhere, the car has been driven there to begin with. With the petrol held inside the tank alone, it is emptied and flushed right where it stands, and nothing more is needed.
Started for a moment, or only the ignition on. Petrol has come out of the tank and got to the filter and the fuel lines, because the system has been primed. Drain, flush, deal with the filter: still normally easy.
A few miles driven, and your pump has spent every one of them labouring on diluted fuel. The work is that tank, your lines, the fuel filter and clean fuel through the entire circuit, and how hard the vehicle was driven matters as much as how far. Driving the kids to the local primary school is one sort of trip. Any miles on the M77, under 15 miles from Mayfield, means your engine has worked hard throughout, and a run to Glasgow, under 50 miles away, makes a very different job as well.
Driven till it protested. Knocking, an uneven idle, smoke, a throttle that has gone soft. That is the motor telling you its fuel has stopped behaving like diesel. Pull up wherever you are — the verge on Mayfield Road, a lay-by, a side street — then leave it there. The drain and flush-through still come first, and they take care of it: when a car is pulled over early, permanent damage is very rare.
Stories Mayfield motorists hear about petrol in a diesel
Myth: topping up to full with diesel makes it fine. It doesn't. Nothing is removed by topping up — you're left with a fuller tank, still the same mixture. That guidance presumes 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 opposite. A modern diesel runs its fuel through smaller components at higher pressure, which makes the lubrication count more, not less.
"It starts, it drives, and so no harm done" — the myth that catches most motorists than any other. Diesel in a petrol motor usually leaves a motor that won't run: the motorist stops, and so does the harm. Feed petrol to a diesel and it generally fires up, idles and drives away like nothing happened — all while its pump wears. Being able to run isn't proof of being fine.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a separate problem. What petrol has weakened stays diluted, and that petrol stays in that tank anyway.
Once your engine has been run, part of that petrol is in your filter and the fuel lines, not the tank — and your next start pulls it right back through your pump. So the myth "drain that tank yourself and you're sorted" doesn't stand up. It is also truly hazardous to drain petrol into a can at the kerbside.
Petrol in a diesel: how does it take place?
No one does it on purpose, and it's seldom carelessness. One way only, because of the nozzles: the slimmer petrol one slides inside a diesel filler with almost no resistance, whereas the diesel one generally will not fit a petrol car. That is how the forecourt makes it easy.
When habit and your car stop matching, it takes place. Any vehicle that's new to you — a hire car, on loan as a courtesy car, or just bought. Households running one of each, petrol and diesel. A forecourt you know, only with its pumps laid out differently. Rushing for a train at Stevenston and filling up en route. Years of petrol cars behind you, a diesel Volkswagen Passat in front of you on the forecourt for its first tank — that's when. Add a back seat full of children, a phone call or rain, and the hand wins.
Avoiding petrol in a diesel next time you fill up in Mayfield
- Check the pump, not the colour. In the UK unleaded handles are normally green and diesel black, but not on each forecourt. The label is what matters.
- The first fill in a strange vehicle is the time to check your filler flap — inside it, or on the cap, many vehicles state the fuel to use.
- Good intentions count for less than a sticker or a fob in a vivid colour on the diesel's key if a household has one of each. So mark it.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the petrol pump. It seems daft and it does the trick.
- Mistakes like this are straightforward to make while your mind is on something else, and so your phone goes away.
- Add-on devices are available for cars without one, and some diesels are built with a filler that won't accept a petrol nozzle. Useful — but a backstop only, never a reason to stop checking the label.
- Stop as soon as you notice. Less petrol in that tank means a thinner blend. It doesn't change what to do next, which is still not to start it.
Put petrol in a diesel around Mayfield already?
The order of things is short, then. Do not crank it, and do not turn your ignition on. If you're still on the forecourt — Esso or anywhere else — ask the attendants to help you roll it clear of the petrol pump. Then phone 0333 366 0103 and tell us what went in, roughly how much, and whether it's run.
Corrosion and deposits form the problem with AdBlue, where petrol brings lost protection. So if it was AdBlue, say so — and see its own Mayfield page.
Mayfield petrol in a diesel jobs: why one costs more than another
An honest single quote doesn't exist here: four scenarios, four separate tasks. What moves your cost is mostly which of them you are in. Where the car is matters too, and whether our van can safely get to it, after the ratio of petrol to what that tank takes.
That's why we ask three questions before quoting instead of after: what was put in, how much, and if it has run. A range becomes a straight figure when the answers are in.
About Mayfield and its setting
Mayfield is a coastal suburban area in North Ayrshire, situated near the towns of Stevenston and Saltcoats. Mayfield has a relatively low elevation of 29 metres and is located approximately 25 miles from Glasgow. Mayfield is characterized by its terraced housing and is part of the wider conurbation along the Ayrshire coast. Mayfield is also within commuting distance to Glasgow, Scotland's largest city.
Mayfield and North Ayrshire: where our fuel drain cover runs
The teams answering petrol in diesel calls around Mayfield, in the KA postcode area, equally work the spots around it, Stevenston, Auchenharvie and Saltcoats included. The car does not need to come to us: our technicians drain at a forecourt, in a supermarket car park, in a lay-by or on your own drive.
In Mayfield and still at the petrol pump?
In that case, you couldn't be in a better position. Keep it off. Ring.