How Worried Should You Be? Petrol in a Diesel Car in Redhill
Unstarted? Then less anxious than you likely are. Everyone around Redhill begins with "have I ruined it?", and the honest answer is generally no: petrol resting inside that tank of any diesel stays harmless till priming, cranking or driving draws it into the system. To leave the vehicle like that, phone Petrol in Diesel then leave the engine switched off. The rest of this page sets out what petrol really does to a diesel, how to tell how far it has got, and how to make sure it doesn't happen to you a second time.
Your engine and petrol in a diesel: what goes on
Passing through an engine, diesel does two jobs at once. Before it ignites, it protects — then it combusts. Extremely fine tolerances go into the injectors and your high-pressure pump, and only your diesel running through keeps those surfaces from grinding together.
The second job petrol does not do at all, and the first it does badly. It's thinner than diesel and removes the lubrication the fuel system depends on, and 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.
The shape of the problem is clear when you put those together. The damage is done by circulation, not by contact. All a tank with petrol in it amounts to is a fuel problem. Whatever a worn pump sheds goes on, carried by the fuel, into your injectors downstream, which is why a pump that has worked on the petrol is where a mechanical problem starts.
How serious is petrol in a diesel? Four situations we see around Redhill
Filled up, and not started: no case is better. On a forecourt, and truly only there, that petrol is still limited to the tank — since everywhere else your car was driven to get to it. The task is draining and flushing on the spot.
Ignition on, or started for a moment. Petrol has left your tank and reached the filter and your lines, because the fuel system has been primed. That is generally still a simple task — a drain, a flush, and your filter dealt with.
Driven a few miles. Now the pump has spent those miles labouring on diluted fuel. How hard your car was driven matters as much as how far, and this work covers that tank, the lines, the fuel filter and fresh fuel through the whole circuit. On the school run to Marlbrook Primary School, the miles is short. Getting as far as Hereford, under 3 miles away, makes a very different task — as does any miles on the M50, under 15 miles from Redhill, with the motor labouring hard the whole time.
Driven until it protested. Clattering, a lumpy idle, smoke, a throttle that has gone soft. That is the motor telling you its fuel has stopped acting like diesel. Whether it is the verge on Laysters Avenue, a lay-by or a side road, stop where you are and leave it. The drain and flush still come first, and they deal with it: when a vehicle is stopped soon, lasting damage is very uncommon.
What Redhill motorists get told about petrol in a diesel — and the myths in it
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It won't. A fuller tank of the same mix is all you get, because topping up takes out nothing. That advice assumes a diesel fuel system handles petrol by percentage. It doesn't.
Myth: a newer diesel copes with a bit of petrol. Rather, the opposite. Lubrication matters more on newer diesels, not less, since their fuel passes through smaller components at higher pressure.
Myth: "If it starts and drives, there is no damage done." This is the one that catches people. A petrol engine fed diesel generally won't run, so the motorist stops and the harm stops with them. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually does; meanwhile your pump grinds. Being able to run isn't proof of being fine.
Not so: a two-stroke additive lets you to drive home. It was an old workaround, meant for another issue. That petrol is still in your tank afterwards, and what it has diluted is not put back.
If the engine has run, part of the petrol sits in the filter and the fuel lines, not the tank — and the next start sends it straight back through your pump. So the myth "drain the tank yourself and you are sorted" doesn't stand up. Clearing petrol into a can at the roadside is also truly risky.
How it happens: petrol in a diesel
Nobody does it on purpose, and it's seldom carelessness. 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 car at all. So the mistake runs one way.
When habit and the vehicle stop matching, it occurs. A motor that is new to you — a hire car, on loan as a courtesy car, or brand new. A household with one petrol and one diesel on the driveway. Your normal forecourt, its pumps suddenly in a different order. A train to catch, and a hurried fill on the way to Hereford. Precisely the moment it takes place: after years of driving petrol, a driver fills a diesel Volkswagen Golf for the first time. Your hand does what it has always done once you add rain, a phone call or a back seat full of kids.
Avoiding petrol in a diesel next time you fill up around Redhill
- The label is what counts, and so read the pump rather than the colour: in the UK unleaded handles are usually green and diesel black, but not on each forecourt.
- The first fill in a new car is the time to check the filler flap — on it, or on the cap, plenty of cars state which fuel to use.
- One of each in the house? Label your key to the diesel — a bright fob, a sticker — since meaning to remember isn't enough.
- It sounds silly and it works: on your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the pump.
- Mistakes like this are straightforward to make whilst your mind is on something else, so your phone goes away.
- Some diesels have a filler built to block a petrol nozzle, and devices you can add exist for vehicles without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop checking the petrol pump.
- Spotting it halfway? Stop there and then. A thinner mixture follows from less petrol in the tank, but the next step stays the same: do not crank it.
Put petrol in a diesel in Redhill already?
Then, there is only a short order of things. Leave it unstarted, with the ignition switched off as well. Ask the staff to help you roll it clear of the petrol pump if you are still at the forecourt, whether that is Hinton Service Station or anywhere else. Next, 0333 366 0103. We'll ask what went in, about how much, and if it's been run.
Corrosion and deposits are the trouble with AdBlue, whereas petrol brings lost protection. So if it was AdBlue, say so — and read its own Redhill page.
Redhill petrol in a diesel tasks: why one costs more than another
The four situations above are four separate jobs, so no single quote for this would be honest. Chiefly, the cost moves with which one you are in. The ratio counts next, meaning how much of that tank is petrol, followed by the position of your car and whether reaching it is safe for our van.
What went in, how much, and whether it has run — three queries we ask before pricing, not after, for precisely that reason. With the answers, you get a straight figure rather than a range.
About Redhill
Redhill is a suburban area located near the city of Hereford in Herefordshire, England, with a population of around 7006 people. Redhill sits at an elevation of 66 metres, close to the nearby places of Newton Farm, Putson, and Grafton. Redhill is characterized by its predominantly semi-detached housing stock, reflecting the area's residential development. Redhill is situated approximately 1.3 miles from Hereford city centre, making it a convenient location for those working or visiting the city.
Fuel drain cover around Redhill and across Herefordshire
Redhill sits in the HR postcode area, and our vans that answer petrol in diesel call-outs there work the locations around it as well — Newton Farm, Putson and Grafton among them. Our technicians drain wherever your car is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
Redhill: still at the pump?
Nothing beats it: that is where you are. Leave the vehicle switched off, then ring.