Hyde: Petrol in a Diesel Car? How Worried to Be
Probably less than you are now — as long as no one has started the vehicle. Till your ignition primes your pump, the starter turns, or your car is driven, petrol in a diesel tank simply rests there and does no harm. Which makes the truthful reply to the first Hyde question — "have I ruined it?" — normally no. Petrol in Diesel is who to ring, with the motor left off, so it remains that way. Below, this page sets out what petrol really does inside a diesel, how far it may have gone, and how to stop it happening to you again.
What petrol in a diesel does to the motor
On its way through an engine, diesel does two jobs. Oiling comes before burning; it does both. The high-pressure pump and your injectors are made to very fine gaps, and the diesel passing through them is what stops those surfaces from wearing down against one another.
Petrol does the first task badly and the second not at all. The knocking comes from petrol being made 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 the system depends on, and any pump running on that mix is wearing itself.
Together, those make the shape of the issue clear. It is movement that causes the damage, not contact. All a tank with petrol in it amounts to is a fuel fault. A pump that has been labouring on that petrol is the start of a mechanical one, and whatever a worn pump sheds travels on with the fuel to the fuel injectors downstream.
How bad is petrol in a diesel? Four scenarios our technicians see in Hyde
Filled up, never started. The best case there is. On a forecourt, and genuinely only there, the petrol is still limited to your tank — since anywhere else your car was driven to reach it. The task is draining and flushing on the spot.
Started for a moment, or only the ignition on. Once primed, the fuel system has pulled petrol out of the tank up to the filter and your lines. That's normally still an easy task — a drain, a flush, and your filter dealt with.
Some miles driven, and the pump has spent every one of them running on thinned fuel. Tank, lines, filter, then clean fuel run through the entire circuit: that is the work, and the way the car was driven counts as much as the mileage. Driving the children to St George's CofE Primary School is one kind of trip. Very different a second time: a trip to Manchester, under 10 miles away, or some miles on the M67, under a mile from Hyde, where the engine never stopped labouring hard.
Driven on until it protested — clattering, smoke, an uneven idle, a dead throttle. The engine is telling you the fuel is no longer acting like diesel. Leave it where it has stopped: a lay-by, a side street, the verge on Market Street. Long-term damage is very unusual if a vehicle is stopped early, and the fuel drain and flush-through that still come first take care of it.
Myths Hyde drivers hear about petrol in a diesel
False: topping up to full with diesel makes it fine. It doesn't. Topping up removes nothing; it gives you a bigger tank of the same mixture. The idea behind that advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
Not so: a newer diesel copes with a bit of petrol. Rather, the reverse. Protection counts more on newer diesels, not less, because their fuel passes through more precise parts at higher pressure.
Myth: "If it starts and drives, there is no damage done." This is the one that catches motorists. Feed diesel to a petrol engine and it generally will not run, and so the driver stops — and the harm stops with them. Whilst the pump wears, a diesel fed petrol normally starts, idles and drives away as if nothing has happened. Fine and running are not the same thing.
An outdated workaround for a distinct problem lies behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." None of what petrol diluted is put back by it — and later, the tank still contains the petrol.
"Drain it yourself and you are sorted" — a myth, since after it's been running some petrol lies in the filter and lines, ready to go straight back through your pump on the next start. It's also really dangerous to drain petrol into a can by the kerbside.
Petrol in a diesel: how does it happen?
Carelessness is seldom the cause, and nobody means to do it. A diesel nozzle generally won't fit a petrol vehicle, yet the slimmer petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error straightforward, and only in that direction.
Habit and your car getting out of step is when it takes place. Courtesy car, hire car, or a motor that is new. Households running one of each, petrol and diesel. Your ordinary forecourt, its pumps now in a different order. A hurried fill on the way to Hyde Central with a train to catch. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is exactly the moment it happens. With rain, a call coming in, or children to deal with, your hand just does what it always has.
How to avoid petrol in a diesel at your next fill-up in Hyde
- Green for unleaded and black for diesel is usual in the UK — but not on each forecourt. Trust the label on the pump, not the colour.
- Many cars state the fuel inside the filler flap or on the cap, and so check it on the first fill in any motor you do not know.
- 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.
- It seems 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 petrol pump.
- Mistakes like this are simple to make while your mind is on something else, and so your phone goes away.
- A misfuel inhibitor helps, up to a point. Some diesels come with a filler designed to reject a petrol nozzle, and add-on devices are available for vehicles without one. They are a backstop, not a reason to stop reading the petrol pump.
- As soon as you realise, stop: less petrol inside your tank means a thinner mix. What to do next does not change, though — still do not crank it.
Already put petrol in a diesel around Hyde?
In that case, there is only a short order of things. Do not start the car, and do not switch the ignition on. Ask the attendants to help you roll it away from the pump if you are still at the forecourt, whether that is Morrisons or somewhere else. Phone 0333 366 0103 next, with three answers — your fuel, the rough amount, and whether it has run.
Corrosion and deposits are the problem with AdBlue, where petrol means lost lubrication. So if it was AdBlue, say so — and see its own Hyde page.
Why one petrol in a diesel job in Hyde costs more than another
Four separate jobs lie behind the four scenarios above — which is why there's no fair single price. The situation itself does most of the work of moving your cost. Two things come after that: the petrol that went in as a proportion of what your tank holds, then the place the car is in and whether a van can reach it safely.
What went in, how much, and if it has run — three queries our engineers ask before costing, not after, for precisely that reason. A range turns into a straight figure when those answers are in.
About Hyde and where it is
Hyde is a town in Greater Manchester, situated on the banks of the River Tame, with a mix of terraced housing and other residential areas. Hyde sits at an elevation of around 113 metres, approximately 7 miles east of Manchester. Hyde is close to several nearby places, including Kingston and Flowery Field, and is part of the larger North West region. Hyde has a population of around 29,455 people, with a range of local amenities and services.
Across Greater Manchester and around Hyde: fuel drain cover
The vans answering petrol in diesel call-outs in Hyde, in the SK postcode area, also work the places around it, Kingston, The Railway Sidings and Flowery Field included. The car doesn't need to move to us: we drain at a forecourt, in a supermarket car park, in a lay-by or on your own drive.
At the pump around Hyde, right now?
Then, you could not be in a better position. Leave the car turned off, and ring.