How Worried Should You Be? Petrol in a Diesel Car in Wexham Street
Far less than you probably are, provided it has not been started. Until your ignition primes your pump, your starter turns, or your vehicle is driven, petrol in a diesel tank simply waits there and does no harm. Which means the honest reply to the first Wexham Street question — "have I ruined it?" — usually no. Leave the motor off and phone Petrol in Diesel — that keeps it that way. Further down, you will find what petrol actually does inside a diesel, how far it might have gone, and how to stop it happening to you again.
The motor and petrol in a diesel: what goes on
Two tasks fall to diesel on its journey round a motor. Oiling comes before burning; it does both. Extremely fine gaps go into your injectors and your high-pressure pump, and only the diesel flowing through keeps their surfaces from grinding together.
Poorly at the first, not at all at the second: that is petrol. The rattling comes from petrol being designed not to ignite when compressed, which is precisely the reverse of what a diesel needs. On top of that it is runnier than diesel, it strips away the lubrication your system hinges on, and any pump running on that mixture is wearing itself.
The shape of the problem is plain once you put those together. The damage is done by movement, not by contact. All a tank with petrol in it amounts to is a fuel fault. Whatever a worn pump sheds goes on, borne by your fuel, into the injectors further along, which is why a pump that has been working on that petrol is where a mechanical problem begins.
Four scenarios our technicians see in Wexham Street: how bad is petrol in a diesel?
Fuelled, and never started: no case is better. That petrol is inside your tank and just that tank, and the task is a drain and a flush where the vehicle stands. This is the one situation that can only truly occur on a forecourt, as anywhere else your car has been driven to get there.
Your ignition turned on, or a short start. Petrol has left your tank and reached the fuel filter and your lines, since your system has been primed. Drain, flush, see to the fuel filter: still usually simple.
Driven a few miles. Now your pump has spent those miles working on weakened fuel. The work is that tank, the lines, the fuel filter and fresh fuel through the whole circuit, and how hard your car was driven counts as much as how far. Driving the kids to The Stoke Poges School is one kind of trip. Very different a second time: a run to St Albans, under 25 miles away, or some distance on the M40, under 3 miles from Wexham Street, where the motor kept labouring hard.
Driven on till it complained — knocking, smoke, a lumpy idle, a dead throttle. The motor is telling you your fuel is no longer behaving like diesel. Whether it's the verge on Tubwell Road, a lay-by or a side street, stop there then leave it. Long-term damage is very unusual when a car is stopped quickly, and the drain and flush that still come first take care of it.
Petrol in a diesel myths Wexham Street people hear
False: topping up to full with diesel makes it fine. It doesn't. A bigger tank of the same mixture is all you get, because topping up takes out nothing. That guidance presumes a diesel fuel system handles petrol by percentage. It does not.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the opposite. Protection matters more on current diesels, not less, because their fuel passes through more precise parts at higher pressure.
This is the one that fools motorists. Myth: "If it starts and drives, there's no harm done." Diesel in a petrol motor normally means a motor that will not run: the motorist stops, and so does the damage. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually does; meanwhile the pump grinds. Being able to run is not the same as being fine.
Myth: a two-stroke additive makes it safe to drive home. It is an old workaround, supposed for another problem. What petrol has diluted remains diluted, and the petrol stays in the tank regardless.
Myth: "Drain the tank yourself and you are sorted." Once the motor has run, some of the petrol is no longer in that tank: it is in the fuel filter and the fuel lines, and it goes right back through the pump on your next start. It is also really dangerous to drain petrol into a can by the kerbside.
Why petrol in a diesel occurs at all
Nobody does it on purpose, and it's rarely carelessness. A diesel nozzle mostly won't fit a petrol car, yet the slimmer petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake simple, and only in one direction.
The moment routine stops matching your car is the moment it takes place. A new car, a hire car or a courtesy car. Households running one of each, petrol and diesel. A well-known forecourt with the pumps in a different order. A rushed fill on the way to Slough with a train to catch. Years of petrol vehicles behind you, a diesel Renault Megane in front of you on the forecourt for its first tank — that's when. Your hand does what it has always done when you add rain, a phone call or a back seat full of children.
Avoiding petrol in a diesel next time you fill up in Wexham Street
- A green handle for unleaded and black for diesel is normal in the UK — yet not on every forecourt. Go by the label on the pump, not the colour.
- In a car you do not know, look inside the flap over the filler or at the cap before the first fill: many cars state the fuel type there.
- One of each in the household? Label the key to your diesel — a coloured fob, a sticker — since meaning to remember is not enough.
- "Diesel", out loud, before you lift the nozzle — every time a new or hired car needs its first tank. It sounds silly. It works.
- 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 refuse a petrol nozzle, and devices you can add are available for vehicles without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop reading the pump.
- Spotting it halfway? Stop there and then. A weaker mix results from less petrol in that tank, but your next stage remains the same: don't fire it up.
Wexham Street: already put petrol in a diesel?
Short and simple, then, is the order of things. Do not fire it up, and do not switch the ignition on. If you're still at the forecourt — BP or anywhere else — ask the staff to help you push the vehicle clear of the petrol pump. Ring 0333 366 0103 next, with three facts — your fuel, the approximate volume, and whether it has run.
If it was AdBlue instead of petrol, say so. That is a different issue — corrosion and deposits rather than lost protection — and it has its own page for Wexham Street.
Wexham Street petrol in a diesel tasks: why one costs more than another
An honest single quote does not exist here: four situations, four separate jobs. What moves the cost is mostly which of them you are in. After that it is the ratio — how much petrol got in against how much the tank takes — and after that where the car is and whether a technician can get to it safely.
What went in, how much, and if it's run — three queries we ask before costing, not after, for exactly that reason. A range becomes a straight figure when the replies are in.
About Wexham Street
Wexham Street is a small village in Buckinghamshire, situated near the River Colne and close to the neighbouring villages of Stoke Poges and Stoke Green. Wexham Street sits at an elevation of 56 metres, with semi-detached housing being the predominant type of accommodation. Wexham Street is located near Hollybush Hill and is within commuting distance of London, being approximately 19 miles from the city centre. Wexham Street has a population of around 670 residents.
Wexham Street and Buckinghamshire: where our fuel drain cover runs
Wexham Street waits in the SL postcode area, and the teams that answer petrol in diesel jobs there work the spots around it as well — Stoke Poges, Hollybush Hill and Stoke Green among them. The vehicle does not need to come to us: we drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive.
In Wexham Street and still at the pump?
Nothing beats it: that's where you are. Keep it off. Ring.