Goodmayes: Petrol in a Diesel Car? How Worried to Be
Not started? Then less worried than you likely are. Petrol resting in a diesel tank does nothing to your engine until something draws it through the fuel system — your ignition priming your pump, your starter, or the drive on its own. So the fair answer to the first question anyone in Goodmayes asks, "have I ruined it?", is usually no. Petrol in Diesel is who to ring, with the motor left off, and so it stays that way. Further down, this page sets out what petrol really does inside a diesel, how far it might have gone, and how to stop it happening to you a second time.
The motor and petrol in a diesel: what happens
Diesel does two jobs on its way through a motor. Lubricating comes before burning; it does both. Your high-pressure pump and the injectors are made to extremely fine tolerances, and the diesel passing through them is what keeps those surfaces from wearing against each other.
Badly at the first, not at all at the second: that is petrol. A pump running on a petrol mixture is wearing itself out, because petrol is thinner than diesel and takes away the lubrication your fuel system relies on. Petrol is also designed to resist igniting under compression — the opposite of what a diesel needs from its fuel — and that is where any knocking starts.
Put those together and the shape of the issue is clear. Contact doesn't do the damage — circulation does. Petrol in a tank is a fuel fault. Whatever a worn pump sheds goes on, carried by your fuel, into the injectors further along, which is why a pump that has been working on the petrol is where a mechanical fault begins.
Goodmayes, petrol in a diesel: four cases, from mild to significant
The best case there can be: filled up, never started. Only your tank has petrol in it, so the task is draining the tank and rinsing your system where the vehicle sits. This situation can only really happen on a forecourt: anywhere else, your car got there by being driven.
Started for a moment, or only your ignition on. Once primed, the fuel system has drawn petrol out of that tank as far as your filter and your lines. Still usually straightforward: drain, flush, and your filter sorted.
Driven a couple of miles. Now your pump has spent these miles working on diluted fuel. The work is your tank, your lines, the filter and fresh fuel through the whole circuit, and how hard the car was driven counts as much as how far. On the school run to Mayespark Primary School, the mileage is small. Getting as far as London, under 10 miles away, makes a very different task — as does any miles on the M11, under 5 miles from Goodmayes, with your engine working hard all the way.
Driven until it protested. Knocking, a lumpy idle, smoke, a throttle that has gone soft. The fuel is not behaving like diesel any more, and your motor is saying so. Whether it's the verge on Breamore Road, a lay-by or a side road, stop there then leave it. A car pulled over early very seldom has permanent damage, since the drain and the flush-through, which still come first, take care of it.
What Goodmayes motorists get told about petrol in a diesel — and the stories in it
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It will not. Nothing is removed by topping up — you're left with a fuller tank, still the same mixture. The idea behind that guidance — that diesel fuel systems tolerate petrol by percentage — is wrong.
Myth: "A current diesel can cope with a bit of petrol." If anything, the reverse. Lubrication matters more on newer diesels, not less, because their fuel runs through more precise components at higher pressure.
"It starts, it drives, and so no harm done" — the myth that trips up more people than any other. The driver of a petrol engine fed diesel usually has no choice but to stop, since it will not run, and the harm stops there. Feed petrol to a diesel and it generally fires up, idles and drives away like nothing happened — all the while its pump wears. Fine and running are not the same thing.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a separate issue. What petrol has thinned stays thinned, and the petrol stays inside the tank regardless.
If the motor has run, part of the petrol is in the fuel filter and the lines, not your tank — and your next start sends it right back through your pump. So the myth "drain your tank yourself and you are sorted" does not hold. It is also genuinely hazardous to drain petrol into a can at the kerbside.
How it happens: petrol in a diesel
On purpose? Never. Through carelessness? Rarely, if ever. The petrol nozzle is the narrower of the two and slips into a diesel filler with almost no resistance; a diesel nozzle mostly won't go into a petrol motor at all. The forecourt makes it simple, and the mistake runs one way.
Habit and your car getting out of step is how it occurs. A new vehicle, a hire car or a courtesy car. One petrol and one diesel on the driveway of the same household. A forecourt you know, but with its pumps laid out differently. Filling up in a hurry on the way to the nearest station, with a train to catch. A new-to-you diesel Volkswagen Passat, its first fuelling, and a driver accustomed to petrol: precisely when it takes place. Throw in rain, a phone call or a back seat full of kids, and your hand does what it has always done.
How to avoid petrol in a diesel at your next fill-up around Goodmayes
- Read the pump, not the colour. In the UK unleaded handles are generally green and diesel black, yet not on each forecourt. The label is what counts.
- The first fill in a new vehicle is the time to check your 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 vivid colour on your diesel's key when 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 motor, say "diesel" aloud. Daft, perhaps, but it does the trick.
- Whilst you're thinking about something else, this is an easy mistake to make — so tuck your phone away.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler built to block a petrol nozzle, and add-on devices exist for the rest. Treat it as a safety net, then keep reading the petrol pump.
- Spotting it halfway? Stop at once. A thinner mix follows from less petrol in that tank, but your next stage stays the same: do not fire it up.
Petrol already in a diesel in Goodmayes? Begin here
Then the order of things is brief. Starting it is out, and so is switching on the ignition. Ask the attendants to help you push it clear of the petrol pump if you are still at the forecourt, whether that's JET or anywhere else. What was put in, about how much, and whether it's run: tell us that when you ring 0333 366 0103.
Corrosion and deposits form the problem with AdBlue, where petrol brings lost protection. So if it was AdBlue, say so — and read its own Goodmayes page.
What makes one Goodmayes petrol in a diesel job cost more than the next
Four different tasks lie behind the four situations above — which is why there is no honest single quote. The situation itself does most of the work of moving your cost. Two things follow that: the petrol that went in as a share of what your tank holds, then the place your car is in and whether a technician can get to it safely.
What was put in, how much, and whether it's run — three questions our engineers ask before quoting, not after, for exactly that reason. Given the answers, there is a straight figure instead of a range.
About Goodmayes
Goodmayes is a suburban area in east London, situated near the River Roding at an elevation of around 14 metres. Goodmayes is located approximately 10.8 miles from central London and is close to nearby places such as Seven Kings, Newbury Park, and Becontree. Goodmayes has a population of around 15,205 people and is characterised by predominantly terraced housing. Goodmayes is a residential community with a mix of local amenities and transport links to London.
Across Greater London and around Goodmayes: fuel drain cover
Goodmayes rests in the IG postcode area, and the vans that answer petrol in diesel calls there work the spots near it as well — Seven Kings, Newbury Park and Becontree among them. 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.
Goodmayes: still at the pump?
Then you are in the best position there is. Keep it off. Ring.