How Worried Should You Be? Petrol in a Diesel Car in Preston Brook
Unstarted? Then less anxious than you likely feel. Till your ignition primes the pump, your starter cranks, or your vehicle is driven, petrol in a diesel tank just rests there and does no harm. Which means the honest reply to that first Preston Brook query — "have I wrecked it?" — normally no. To leave the car that way, ring Petrol in Diesel then leave the motor alone. Further down, this page sets out what petrol really does inside a diesel, how far it may have got, and how to stop it happening to you again.
Petrol in a diesel: what does it do to your engine?
Diesel has two tasks on its way through a motor. Before it combusts, it protects — and then it combusts. What stops the surfaces inside the high-pressure pump and the fuel injectors from grinding against one another is the diesel flowing through them — they're made to very fine gaps.
Badly at the first, not at all at the second: that is petrol. It is runnier than diesel and removes the protection the fuel system hinges on, so a pump running on a petrol mix 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's where the rattling comes from.
Put these together and the shape of the issue is clear. Contact does not do the harm — movement does. All a tank with petrol in it amounts to is a fuel issue. The beginning of a mechanical problem is a pump that has been labouring on that petrol — and whatever a worn pump sheds moves on with the fuel to your injectors downstream.
Four situations our engineers see around Preston Brook: how serious is petrol in a diesel?
The best case there can be: filled up, never started. Being at a forecourt is what makes this the case: elsewhere, the vehicle has been driven there to begin with. With the petrol held in the tank alone, it's emptied and cleaned right where it stands, and nothing more is needed.
Ignition on, or started for a moment. With your system primed, the lines and filter already contain petrol that came from the tank. Still generally simple: drain, flush, and your filter sorted.
The pump has worked a couple of miles on thinned fuel — that is what driving the car does. The work is your tank, the lines, the filter and fresh fuel through the entire circuit, and how hard the car was driven counts as much as how far. On the school run to Gorsewood Primary School, the miles is short. A run as far as Chester, under 15 miles away, is a very different job. So is any distance on the M56, under a mile from Preston Brook, where your engine has been working hard the whole time.
Driven until it protested. Knocking, a lumpy idle, smoke, a throttle that has gone soft. The motor is telling you your fuel is no longer behaving like diesel. Pull up on the spot — on the verge on Hilltop Road, at the kerb, down a side road — and don't move it again. What comes first is still the fuel drain and flush-through, and that deals with it, with lasting damage very rare when a vehicle is stopped early.
Stories Preston Brook people hear about petrol in a diesel
False: 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 mix. That guidance supposes a diesel fuel system handles petrol by percentage. It doesn't.
Myth: a newer diesel copes with a bit of petrol. Rather, the reverse. A newer diesel sends its fuel through smaller parts at higher pressure, which makes the protection matter more, not less.
This is the one that catches people. Myth: "If it starts and drives, there's no harm done." A petrol motor fed diesel generally won't run, and so the driver stops and the damage stops with them. While the pump grinds, a diesel fed petrol normally starts, ticks over and drives away as if nothing has happened. Running isn't the same as fine.
Myth: "Add some two-stroke oil and drive the car home." It's an old fix for a distinct problem. What petrol has weakened remains thinned, and that petrol stays in the tank anyway.
Once the engine has been run, part of that petrol is in your filter and your lines, not that tank — and your next start pulls it straight back through your pump. So the myth "drain the tank yourself and you're sorted" doesn't hold. It is also genuinely dangerous to drain petrol into a can by the kerbside.
Why petrol in a diesel takes place at all
A careless moment is rarely the cause, and no one means to do it. The forecourt makes it simple: the petrol nozzle is the smaller of the two, and it slips into a diesel filler with almost no resistance, while a diesel nozzle generally will not go into a petrol vehicle at all. So the error runs one way.
The moment habit stops matching your car is the moment it takes place. Courtesy car, hire car, or a car that's brand new. Two motors on one drive, one petrol, one diesel. The pumps in a different order on a familiar forecourt. Racing for a train at Runcorn East and fuelling up en route. The first fill-up in a diesel Renault Megane after years of driving petrol is precisely the moment it occurs. With rain, a call arriving, or a car full of children to deal with, the hand just does what it always has.
Preston Brook drivers: how to prevent petrol in a diesel next time
- Green for unleaded and black for diesel is usual in the UK — yet not on each forecourt. Go by the label on the pump, not the colour.
- The first fill in an unfamiliar motor is the time to check the filler flap — inside it, or on the cap, many vehicles state the fuel they take.
- Mark the key. In a household with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of intending to remember.
- "Diesel", aloud, before you pick up the nozzle — each time a new or hired car needs its first tank. It sounds daft. It does the trick.
- Thinking about something else is when this becomes an easy mistake to make, so put the phone away and keep your mind on the petrol pump.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler designed to block a petrol nozzle, and add-on devices exist for cars without one. They are a backstop, not a reason to stop checking the pump.
- The moment you notice, stop: less petrol in your tank means a thinner mixture. What to do next does not change, though — still don't fire it up.
Put petrol in a diesel around Preston Brook already?
The order of things is short, then. Leave it unstarted, with the ignition switched off too. Yet at the forecourt, at Shell or anywhere else? Ask the staff to help you roll it clear of the petrol pump. Next, 0333 366 0103. We will ask what went in, roughly how much, and if it has been run.
If it was AdBlue instead of petrol, say so. That's a different issue — corrosion and deposits and not lost protection — and it has its own page for Preston Brook.
Preston Brook petrol in a diesel jobs: why one costs more than another
Four different tasks lie behind the four situations above — which is why there's no honest single quote. What shifts the cost is chiefly which of them you are in. Where the vehicle is counts too, and whether our van can safely reach it, after the share of petrol to what that tank holds.
That's why we ask three questions before pricing instead of after: what went in, how much, and if it's run. The answers change a range into a straight figure.
About Preston Brook itself
Preston Brook is a small suburban area in Cheshire, situated near the coast at an elevation of 34 metres. Preston Brook lies close to the nearby settlements of Preston on the Hill, Whitehouse, and Murdishaw, and is approximately 13.5 miles from Chester. Preston Brook has a population of around 1067 people, predominantly living in terraced housing.
Preston Brook and Cheshire: where our fuel drain cover reaches
Preston on the Hill, Whitehouse and Murdishaw are among the spots near Preston Brook that the same vans work, answering petrol in diesel call-outs across Preston Brook's WA postcode area. Our technicians drain wherever the vehicle is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
Preston Brook: still at the pump?
Then you're in the best position there can be. Switched off it stays; then call.