Grange: Petrol in a Diesel Car? How Worried to Be
If it hasn't been started, you can worry far less than you likely are. "Have I ruined it?" is the first question anyone in Grange asks, and the truthful answer is usually no, since petrol resting in a diesel tank hurts nothing until it's dragged through the fuel system — by ignition priming, by the starter, or by driving. Leave your engine off then phone Petrol in Diesel — that is how you keep it like that. The rest of this page sets out what petrol actually does to a diesel, how to judge how far it has got, and how to make sure it doesn't happen to you a second time.
Petrol in a diesel: what does it do to your engine?
Two tasks fall to diesel on its journey round a motor. It combusts, and before it ignites it protects. What keeps the surfaces inside the high-pressure pump and the fuel injectors from wearing down against each other is the diesel flowing through them — they are designed to very fine clearances.
Of these two jobs, petrol manages the first poorly and the second not at all. It's runnier than diesel and removes the protection the fuel system depends on, and so a pump running on a petrol mix is a pump wearing itself. And petrol is made to resist igniting under compression, which is the reverse of what a diesel needs from its fuel. That's where the rattling comes from.
The shape of the problem is clear once you put those together. It's movement that causes the damage, not contact. Where the petrol is only inside the tank, it is an issue of fuel, nothing more. Whatever a worn pump sheds travels on, carried by the fuel, into the fuel injectors further along, which is why a pump that has been working on the petrol is where a mechanical problem begins.
Four scenarios we see in Grange: how serious is petrol in a diesel?
Filled up, and never started: no case is better. That petrol is in your tank and just the tank, and the job is a drain and a flush where your car sits. This is the one situation that can only truly take place at a forecourt, since anywhere else the car has been driven to get there.
Ignition on, or started for a moment. With your system primed, your lines and filter already hold petrol that has come from the tank. Drain, flush, deal with the filter: still normally easy.
Driven a couple of miles. Now your pump has spent those miles running on weakened fuel. Distance is only half of that; how hard it was driven matters just as much. Either way the work includes that tank, your lines, your filter and fresh fuel through the whole system. The school run to Black Horse Hill Infant School is one matter. Any distance on the Moreton Spur, under 3 miles from Grange, means your engine has worked hard throughout, and a run to Liverpool, under 10 miles away, is a very different task as well.
It protested, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone lumpy. That's your engine telling you its fuel has stopped behaving like diesel. Whether it is the verge on Grafton Walk, a lay-by or a side street, stop where you are then leave it. A car pulled over quickly very rarely has long-term damage, because the drain and the flush-through, which still go first, sort it out.
Grange people and that petrol in a diesel stories they hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Nothing is removed by topping up — you're left with a fuller tank, still the same mix. The assumption behind the guidance — that diesel fuel systems tolerate petrol by percentage — is wrong.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the opposite. A current diesel sends its fuel through finer parts at higher pressure, which makes the lubrication matter more, not less.
Myth: "If it starts and drives, there's no damage done." This is the one that catches people. Feed diesel to a petrol engine and it usually will not run, and so the driver stops — and the damage stops with them. A diesel fed petrol normally starts, idles and drives away as if nothing has happened, while the pump wears. Running is not the same as fine.
An outdated fix for a distinct issue is behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." The petrol is still in the tank after that, and what it has thinned is not put back.
If your engine has run, part of that petrol sits in the fuel filter and the fuel lines, not your tank — and the next start sends it right back through the pump. So the myth "drain the tank yourself and you are sorted" doesn't hold. On top of that, petrol drained into a can by the road is truly dangerous.
How does petrol in a diesel occur?
On purpose? Never. Through carelessness? Seldom, if ever. The forecourt makes it easy: the petrol nozzle is the smaller of the two, and it slips into a diesel filler with almost no resistance, whilst a diesel nozzle generally won't go into a petrol vehicle at all. So the slip runs one way.
It occurs when habit and your car stop matching. Courtesy car, hire car, or a motor that's new. A household with one petrol and one diesel on the drive. A well-known forecourt with the pumps in a different order. A train to catch, and a rushed fill on the way to West Kirby. 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 at your next fill-up around Grange
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, though most usually do. Check the pump's label; the colour is only a hint.
- In a car you do not know, look inside the flap over the filler or at the cap before your first fill: many cars state the fuel there.
- Mark your key. In a home with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember.
- "Diesel", out loud, before you lift the nozzle — every time a new or hired car needs its first tank. It seems daft. It works.
- Mistakes like this are straightforward to make while your mind is on something else, and so your phone goes away.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler designed to reject a petrol nozzle, and aftermarket devices are available for the rest. Count it as a safety net, and keep reading the pump.
- The moment you notice, stop: less petrol inside that tank means a weaker mixture. What to do next does not change, though — still do not crank it.
Petrol already in a diesel around Grange? Start here
Short and simple, then, is the order of things. Leave it unstarted, with your ignition off as well. Still on the forecourt, at Morrisons or anywhere else? Ask the attendants to help you roll it away from the petrol pump. Ring 0333 366 0103 next, with three answers — your fuel, the rough volume, and whether it has run.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost protection, make it a separate fault — Grange has a page just for it.
What makes one Grange petrol in a diesel job cost more than the next
There is no fair single price for this, since the four situations above are four separate tasks. Mostly, your cost moves with which situation you are in. Two things follow that: the petrol that got in as a share of what the tank holds, then the spot the car is in and whether our van can reach it safely.
What went in, how much, and whether it's run — three questions our technicians ask before pricing, not after, for precisely that reason. Those answers are what turn a range into one firm number.
About Grange and where it is
Grange is a suburban area on the Wirral Peninsula in Merseyside, situated near the coast and approximately 8 miles from Liverpool. Grange has a mix of housing types, but semi-detached homes are predominant in the area. Grange is close to nearby places such as West Kirby, Newton, and Caldy, and its elevation is around 48 metres above sea level. Grange is part of the larger North West region, about 182 miles from London.
Across Merseyside and in Grange: fuel drain cover
The vans answering petrol in diesel calls around Grange, in the CH postcode area, also work the locations around it, West Kirby, Newton and Caldy included. You need not move your car to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all spots we drain.
In Grange and still at the petrol pump?
Then, you could not be in a better position. Leave it switched off, and ring.