Kingsway: Petrol in a Diesel Car? How Worried to Be
Provided it hasn't been started, you can worry less than you likely are. Till the ignition primes the pump, your starter cranks, or the vehicle is driven, petrol in a diesel tank just sits there and does no harm. Which makes the truthful reply to that first Kingsway query — "have I wrecked it?" — usually no. Keep it that way: leave your motor off and ring Petrol in Diesel. Below, 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.
What petrol in a diesel does to the motor
Two tasks fall to diesel on its route through a motor. Before it ignites, it protects — and then it combusts. Your high-pressure pump and the injectors are made to extremely fine clearances, and your diesel passing through them is what stops those surfaces from wearing against one another.
Of those two jobs, petrol manages the first poorly and the second never. Being less viscous than diesel, petrol strips out the lubrication a fuel system needs, so a pump on that mixture wearing itself. It is equally made to resist igniting under compression — the opposite of what a diesel needs — which is why you hear the knocking.
Seen together, they show the shape the issue takes. Not contact but circulation is what does the damage. All a tank with petrol in it amounts to is a fuel problem. The beginning of a mechanical problem is a pump that has been working on that petrol — and whatever a worn pump sheds travels on with the fuel to the fuel injectors beyond it.
How serious is petrol in a diesel? Four situations our technicians see in Kingsway
Fuelled up, never started. The best case there can be. On a forecourt, and genuinely only there, that petrol is still limited to your tank — since everywhere else the car was driven to get to it. The task is draining and rinsing on the spot.
A moment's running, or merely the ignition on. The system has been bled, so petrol has left the tank and got to your filter and the lines. Still generally straightforward: drain, flush, and the filter seen to.
Driven a few miles. Now your pump has spent those miles running on thinned fuel. How hard your car was driven matters as much as how far, and this work takes in that tank, the lines, the fuel filter and clean fuel through the entire system. Driving the kids to Kingsway Primary Academy School is one kind of trip. A run as far as Liverpool, under 15 miles away, is a very different job. So is any miles on the M62, under 3 miles from Kingsway, where your engine has been labouring hard the whole time.
Driven until it protested. Knocking, a lumpy idle, smoke, a throttle that has gone soft. The motor is telling you your fuel is no longer acting like diesel. Leave it wherever it stops: a lay-by, a side street, the verge on Milton Road. What goes first is still the fuel drain and flush-through, and that deals with it, with lasting damage very unusual when a car is pulled over early.
Kingsway motorists and that petrol in a diesel stories they hear
Myth: topping up to full with diesel makes it fine. It doesn't. A bigger tank of the same mixture is all it gives, since topping up takes out nothing. Percentage isn't how a diesel fuel system copes with petrol, however much that advice supposes.
If anything, the opposite holds. Myth: "A modern diesel can cope with a bit of petrol." Smaller components and higher pressure are how a current diesel runs its fuel, and that makes the protection matter more, not less.
This is the one that fools people. Myth: "If it starts and drives, there's no damage done." The motorist of a petrol engine fed diesel normally stops, since it will not run, and the damage stops there. A diesel fed petrol generally starts, idles and drives away as if nothing has happened, whilst your pump wears. Being able to run is not the same as being fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a separate issue. That petrol is still inside that tank after that, and what it has weakened isn't put back.
If the motor has been run, part of that petrol sits in the fuel filter and the fuel lines, not your tank — and your next start pulls it straight back through your pump. So the myth "drain the tank yourself and you're sorted" doesn't stand up. Draining petrol into a can by the kerbside is also really risky.
Why petrol in a diesel occurs at all
On purpose? Never. Through carelessness? Rarely, if ever. A diesel nozzle mostly won't go into a petrol motor, but the smaller petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error simple, and just in one direction.
It takes place when habit and the car stop matching. Courtesy car, hire car, or a vehicle that's brand new. Two cars on one driveway, one petrol, one diesel. Your normal forecourt, its pumps suddenly in a different order. Racing for a train outside Widnes and fuelling up en route. Exactly the moment it occurs: after years of driving petrol, someone fills a diesel Volkswagen Passat for the first time. With rain, a call arriving, or children to deal with, the hand just does what it always has.
Kingsway drivers: how to avoid petrol in a diesel next time
- Read the pump, not the colour. In the UK unleaded handles are generally green and diesel black, but not on every forecourt. The label is what matters.
- Plenty of motors state the fuel type inside your filler flap or on the cap, so check there on the first fill in a vehicle you do not know.
- One of each in the household? Label your key to the diesel — a bright fob, a sticker — since meaning to remember isn't enough.
- It sounds daft and it works: on your first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the pump.
- Thinking about something else is when this becomes an easy mistake to make, and so tuck the phone away and keep your mind on the petrol pump.
- 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 cars without one. They are a backstop, not a reason to stop reading the petrol pump.
- Less petrol makes a thinner blend, and so stop as soon as you realise — though remembering that your next step is unchanged. It is still not to crank it.
Put petrol in a diesel in Kingsway already?
The order of things is brief, then. Leave it unstarted, with your ignition off as well. Still on the forecourt, at Esso or anywhere else? Ask the attendants to help you roll the vehicle clear of the pump. Then call 0333 366 0103 and tell us what was put in, roughly how much, and if it's run.
If it was AdBlue instead of petrol, say so. That is a different problem — corrosion and deposits instead of lost lubrication — and it has its own page for Kingsway.
Kingsway petrol in a diesel tasks: why one costs more than another
An honest single quote does not exist here: four situations, four separate jobs. Which of them you're in is mostly what shifts the cost. After that it's the ratio — how much petrol went in against how much the tank holds — and then where your car is and whether a technician can reach it safely.
Before any quote, not after, come three questions: the fuel that was put in, the quantity, and whether it's run. That is why. Given the replies, there is a straight figure instead of a range.
About Kingsway
Kingsway is a suburban area in Cheshire, situated near the coast and approximately 10 miles from Liverpool. Kingsway has a relatively low elevation of 11 metres above sea level and is surrounded by other nearby places such as Widnes and Newtown. Kingsway is characterised by its predominantly semi-detached housing stock, which reflects the typical residential development of the region. Kingsway is also located within commuting distance of major cities, with London being around 169 miles away.
Fuel drain cover across Cheshire, Kingsway included
Widnes, Newtown and Simms Cross are among the spots near Kingsway that the same vans work, answering petrol in diesel calls across Kingsway's WA postcode area. The car doesn't need to come to us: our engineers drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
At the petrol pump around Kingsway, right now?
The best position there is, then — that is where you are. Phone, and leave it turned off.