Should You Worry? Petrol in a Diesel Car in Purley
Provided it hasn't been started, worry less than you likely are. Petrol resting in a diesel tank does nothing to your engine till something draws it through your fuel system — the ignition priming your pump, the starter, or driving itself. So the fair answer to the first query anyone in Purley asks, "have I ruined it?", is usually no. To leave it that way, call Petrol in Diesel and leave your motor switched off. What petrol actually does to a diesel, how to judge how far it's travelled, and how to stop it from happening again: that is the remainder of this page.
What petrol in a diesel does to the engine
Passing through a motor, diesel does two jobs at the same time. It protects to begin with, and only then does it burn. Built to very fine clearances, the injectors and the pump rely on your diesel moving through them to stop their surfaces wearing against one another.
Of those two jobs, petrol manages the first poorly and the second not at all. It's thinner than diesel and strips away the lubrication your fuel system rests on, 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 opposite of what a diesel needs from its fuel. That is where the clattering comes from.
Combined, those make the shape of the trouble clear. Not contact but circulation is what does the harm. Where the petrol is only in that tank, it's a fault of fuel, nothing more. After your pump has been labouring on that petrol, a mechanical fault has started: anything shed by a pump that's grinding travels onward to your injectors with the fuel.
Petrol in a diesel in Purley: how bad is it? Four cases
Fuelled up, never started. The best case there can be. At a forecourt, and genuinely only there, that petrol is still confined to that tank — since anywhere else the car was driven to reach it. The job is emptying and purging on the spot.
A brief spell of running, or just the ignition on. Petrol has left that tank and got to your filter and the lines, since your system has been primed. Drain, flush, see to the filter: still usually simple.
Your pump now spent a few miles on weakened fuel — that is what driving it does. How hard your car was driven matters as much as how far, and the work takes in that tank, your lines, your filter and clean fuel through the entire system. A school run to Christ Church CofE Primary School (Purley) is one thing. Very different a second time: a run to Westminster, under 15 miles away, or any miles on the M23, under 5 miles from Purley, where the engine never stopped labouring hard.
Driven on until it protested — clattering, smoke, an uneven idle, a dead throttle. What you are hearing is the engine reporting fuel that no longer behaves like diesel. Stop wherever you are — the verge on Russell Hill Road, a lay-by, a side street — then leave the vehicle there. The drain and flush-through still come first, and they deal with it: when a vehicle is stopped quickly, long-term damage is very rare.
Purley people and the 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 bigger tank, still the same mix. Percentage is not how a diesel fuel system tolerates petrol, whatever that advice supposes.
"Modern diesels can handle a little petrol" — a myth, and nearer the reverse. Smaller parts and higher pressure are how a current diesel runs its fuel, and that makes the lubrication count more, not less.
This is the one that catches drivers. Myth: "If it starts and drives, there's no harm done." A petrol engine fed diesel generally will not run, and so the driver stops and the damage stops with them. A diesel fed petrol usually starts, idles and drives away as if nothing has happened, while the pump wears. Running does not mean fine.
An old workaround for a separate problem is behind this one. Myth: "Add some two-stroke oil and drive the car home." That petrol is still in the tank afterwards, and whatever it has weakened is not put back.
If your engine has run, part of that petrol sits in your filter and the lines, not your tank — and the next start pulls it straight back through your pump. So the myth "drain the tank yourself and you are sorted" doesn't stand up. It is also genuinely dangerous to drain petrol into a can by the roadside.
How does petrol in a diesel happen?
No one does it on purpose, and it is seldom carelessness. The forecourt makes it easy: the petrol nozzle is the slimmer of the two, and it slides into a diesel filler with almost no resistance, whilst a diesel nozzle mostly won't go into a petrol vehicle at all. So the mistake runs one way.
When habit and the car stop matching, it occurs. A new car, a hire car or a courtesy car. One petrol and one diesel on the driveway of the same household. The pumps in a different order on a well-known forecourt. Filling up in a rush on the way to the nearest station, with a train to catch. A new-to-you diesel Renault Megane, its first fuelling, and a motorist used to petrol: precisely when it takes place. Throw in a back seat full of kids, a phone call or rain, and the hand wins.
Purley motorists: how to prevent petrol in a diesel next time
- Not every forecourt in the UK follows green for unleaded and black for diesel, though most generally do. Check the petrol pump's label; the colour is just a hint.
- The first fill in a new car is the time to check the filler flap — inside it, or on the cap, many cars state which fuel to use.
- Good intentions count for less than a sticker or a fob in a bright colour on the diesel's key if a household has one of each. So mark it.
- Before the nozzle comes off the petrol pump the first time you fill a hired or new motor, say "diesel" out loud. Silly, yes, yet it works.
- Tuck your phone away. This is an easy mistake to make whilst you are thinking about something else.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler built to refuse a petrol nozzle, and add-on devices are available for cars without one. They are a backstop, not a reason to stop reading the petrol pump.
- The moment you notice, stop: less petrol inside the tank makes a weaker mixture. What to do next doesn't change, though — still don't start the vehicle.
Petrol already in a diesel in Purley? Start here
Short and simple, then, is the order of things. Starting it is out, and so is turning on your ignition. If you're still at the forecourt — Tesco or anywhere else — ask the staff to help you roll the car away from the pump. Then ring 0333 366 0103 and tell us what got in, roughly how much, and whether it has run.
Say so if it was AdBlue instead of petrol: it's a separate issue, with its own page for Purley, since AdBlue brings corrosion and deposits rather than lost lubrication.
Purley petrol in a diesel jobs: why one costs more than another
There is no fair single quote for this, since the four scenarios above are four different jobs. The scenario itself does most of the work of moving your cost. After that it's the ratio — how much petrol got in against how much your tank holds — and after that where the vehicle is and whether a van can get to it safely.
What went in, how much, and if it's run — three questions we ask before quoting, not after, for exactly that reason. Given the answers, you get a straight figure rather than a range.
About Purley
Purley is a locality in south London, situated approximately 11.7 miles from central London and 11.2 miles from Westminster. Purley sits at an elevation of around 68 metres, near the North Downs, and is surrounded by nearby places such as Russell Hill, Woodcote, and Riddlesdown. Purley is predominantly composed of flat housing and has a population of around 3874 residents. Purley is a residential area with a mix of local amenities and services.
Purley and Greater London: where our fuel drain cover reaches
Our vans answering petrol in diesel jobs in Purley, in the CR postcode area, equally work the locations around it, Russell Hill, Woodcote and Riddlesdown included. Our engineers drain where your car is — your own drive, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
At the pump around Purley, still?
In that case, you couldn't be in a better place. Ring, and keep it turned off.