How Worried Should You Be? Petrol in a Diesel Car in Hyde Heath
Not started? Then less worried than you probably feel. Everyone in Hyde Heath begins with "have I wrecked it?", and the fair answer is generally no: petrol resting in your tank of any diesel remains harmless till priming, cranking or driving draws it into the system. Leave the motor off and call Petrol in Diesel — that keeps it like that. Below, this page sets out what petrol actually does inside a diesel, how far it might have got, and how to stop it happening to you again.
What petrol in a diesel does to the motor
Two jobs fall to diesel on its journey round a motor. It protects first, and only then does it burn. Made to extremely fine clearances, the injectors and the pump rely on your diesel flowing through them to keep their surfaces from wearing against one another.
Petrol does the first job poorly and the second not at all. It is thinner than diesel and removes the protection your fuel system depends on, and 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.
The shape of the issue is plain when you put those together. Contact doesn't do the harm — circulation does. All a tank with petrol in it amounts to is a fuel fault. The start of a mechanical problem is a pump that has been labouring on that petrol — and whatever a worn pump sheds travels on with your fuel to your injectors downstream.
How serious is petrol in a diesel? Four scenarios we see around Hyde Heath
Fuelled up, never started. The best case there can be. Just your tank has petrol in it, and so the job is emptying the tank and rinsing the fuel system where the car sits. This scenario can only truly occur at a forecourt: anywhere else, your car got there by being driven.
Your ignition turned on, or a brief start. Petrol has come out of that tank and reached the fuel filter and the lines, because the system has been primed. That's generally still an easy task — a drain, a flush, and the fuel filter dealt with.
Some miles driven, and the pump has spent each of them working on thinned fuel. How hard the car was driven counts as much as how far, and this work takes in your tank, the lines, the filter and fresh fuel through the whole circuit. Driving the children to Hyde Heath Infant School is one sort of trip. Very different a second time: a trip to St Albans, under 15 miles away, or some miles on the M40, under 10 miles from Hyde Heath, where the motor kept running hard.
Driven until it complained. Knocking, a lumpy idle, smoke, a throttle that has gone soft. What you are hearing is the engine reporting fuel that no longer runs like diesel. Pull up on the spot — on the verge on Hyde Heath Road, at the kerb, down a side road — and do not move it again. Permanent damage is very uncommon if a car is pulled over early, and the fuel drain and flush-through that still go first deal with it.
What Hyde Heath people get told about petrol in a diesel — and the stories in it
"Top it up the rest of the way with diesel and it will be fine" — a myth. It won't. A bigger tank of the same mix is all it gives, because topping up removes nothing. The idea behind that advice — that diesel fuel systems accept petrol by percentage — is wrong.
"Newer diesels can handle a little petrol" — a myth, and nearer the opposite. More precise components and higher pressure are the way a newer diesel runs its fuel, and that makes the lubrication count more, not less.
The myth that catches people off guard: if it starts and drives, it must be unharmed. The motorist of a petrol engine fed diesel usually has no choice but to stop, because it will not run, and the damage stops there. While your pump wears, a diesel fed petrol normally starts, ticks over and drives away as if nothing has happened. Fine and running aren't the same at all.
An outdated workaround for a separate fault lies behind this one. Myth: "Add some two-stroke oil and drive the car home." None of what petrol thinned gets put back by it — and later, that tank still holds that petrol.
Myth: "Drain your tank yourself and you are sorted." Once your engine has run, some of the petrol is no longer in the tank: it's in the fuel filter and the fuel lines, and it goes right back through the pump on the next start. It is also genuinely risky to drain petrol into a can at the roadside.
How does petrol in a diesel occur?
It's rarely carelessness, and nobody does it on purpose. One way only, because of the nozzles: the smaller petrol one slides inside a diesel filler with almost no resistance, while the diesel one mostly will not fit a petrol vehicle. That's how the forecourt makes it easy.
It takes place when routine and the vehicle stop matching. A new car, a hire car or a courtesy car. Two cars on one drive, one petrol, one diesel. The pumps in a different order on a familiar forecourt. A train to catch, and a hurried fill en route to Great Missenden. A new-to-you diesel Renault Megane, its first fuelling, and a driver accustomed to petrol: precisely when it happens. Add a back seat full of children, a phone call or rain, and habit takes over.
How to prevent petrol in a diesel at your next fill-up around Hyde Heath
- A green handle for unleaded and black for diesel is normal in the UK — yet not on each forecourt. Go by the label on the petrol pump, not the colour.
- The first fill in a new motor is the time to check the filler flap — on it, or on the cap, many vehicles state the fuel they take.
- Good intentions count for less than a sticker or a fob in a bright colour on your diesel's key if a home has one of each. So mark it.
- Before the nozzle leaves the petrol pump the first time you fuel a hired or new vehicle, say "diesel" aloud. Silly, perhaps, but it does the trick.
- While you're thinking about something else, this is an easy mistake to make — so put your phone away.
- Some diesels have a filler designed to refuse a petrol nozzle, and devices you can add exist for cars without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop checking the petrol pump.
- As soon as you notice, stop: less petrol in your tank means a weaker mixture. What to do next does not change, though — still do not start the car.
Already put petrol in a diesel around Hyde Heath?
The order of things is short, then. Starting it is out, and so is switching on your ignition. Still on the forecourt, at the nearest petrol station or anywhere else? Ask the attendants to help you push the car clear of the pump. Then phone 0333 366 0103 and tell us what went in, about how much, and if it has run.
Corrosion and deposits form the issue with AdBlue, where petrol brings lost protection. So if it was AdBlue, say so — and read its own Hyde Heath page.
Why one petrol in a diesel job in Hyde Heath costs more than another
There is no honest single quote for this, because the four situations above are four separate jobs. Which of them you're in is mostly what moves the cost. Where your car is matters too, and whether our van can safely get to it, after the ratio of petrol to what your tank holds.
That is why our engineers ask three questions before costing rather than after: what got in, how much, and if it's run. Their replies are what turn a range into one firm number.
About Hyde Heath, for a moment
Hyde Heath is a small village in Buckinghamshire, situated in the Chiltern Hills at an elevation of around 168 metres. Hyde Heath lies approximately 26 miles northwest of London and 14 miles southwest of St Albans, near the villages of Hyde End and Little Missenden. Hyde Heath has a population of around 717 people, predominantly living in detached houses.
Hyde Heath and Buckinghamshire: where our fuel drain cover runs
Hyde Heath waits in the HP postcode area, and our teams that answer petrol in diesel jobs there work the places near it as well — Hyde End, Little Missenden and Little Wood Corner among them. You need not move the car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all spots we drain.
At the pump around Hyde Heath, still?
The best spot there is, then — that's where you are. Turned off it remains; then ring.