Seacroft: Petrol in a Diesel Car? How Worried to Be
If it hasn't been started, worry far less than you likely are. "Have I ruined it?" is the first question anyone in Seacroft asks, and the truthful answer is generally no, because petrol resting in a diesel tank hurts nothing until it's drawn through your fuel system — by ignition priming, by the starter, or by being driven. Leave the engine off and ring 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 a second time.
Petrol in a diesel: what does it do to your engine?
Two jobs fall to diesel on its route round a motor. It lubricates to begin with, and only then does it burn. The high-pressure fuel pump and your injectors are made to extremely fine clearances, and your diesel passing through them is what keeps those surfaces from wearing down against each other.
Of those two jobs, petrol manages the first badly and the second never. The knocking comes from petrol being designed not to ignite when compressed, which is exactly the reverse of what a diesel needs. On top of that it is runnier than diesel, it strips out the lubrication the system depends on, and any pump running on that mix is wearing itself.
Combined, those make the shape of the trouble clear. Not contact but circulation is what causes the damage. Where that petrol is only in the tank, it is a fault of fuel, nothing more. The beginning of a mechanical one is a pump that has been running on that petrol — and whatever a worn pump sheds travels on with the fuel to the fuel injectors downstream.
Four scenarios our technicians see in Seacroft: how bad is petrol in a diesel?
Fuelled up, never started. The best case there is. On a forecourt, and truly only there, that petrol is still confined to the tank — because everywhere else the vehicle was driven to reach it. The job is emptying and purging on the spot.
A brief spell of running, or just your ignition on. Once primed, the system has pulled petrol out of your tank up to your filter and your lines. Drain, flush, see to the fuel filter: still normally straightforward.
Your pump now spent a couple of miles on diluted fuel — that is what driving the car meant. Mileage is only half of that; how hard it was driven counts just as much. Either way the work includes your tank, the lines, the fuel filter and clean fuel through the whole system. Short trips, such as the school run to The Richmond Primary Academy, are one matter. Very different again: a run to Lincoln, under 50 miles away, or some miles on the M180, under 50 miles from Seacroft, where your engine kept working hard.
Driven on until it protested — rattling, smoke, an uneven idle, a soft throttle. That's the motor telling you its fuel has stopped behaving like diesel. Stop on the spot — on the verge on Albert Avenue, at the kerb, down a side road — and do not move it again. A car pulled over soon very seldom has lasting damage, as the fuel drain and the flush-through, which still go first, sort it out.
What Seacroft drivers get told about petrol in a diesel — and the stories in it
"Top it up the rest of the way with diesel and it will be fine" — a myth. It won't. Nothing comes out when you top up — the tank simply holds more of the same mixture. That advice supposes a diesel fuel system tolerates petrol by percentage. It does not.
"Newer diesels can handle a little petrol" — a myth, and closer to the reverse. At higher pressure, through smaller components: that's how a modern diesel moves its fuel, and so the protection matters more, not less.
Myth: "If it starts and drives, there is no damage done." This is the one that fools people. A petrol engine fed diesel normally will not run, so the driver stops and the damage stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile your pump wears. A running engine does not mean fine.
Myth: "Add some two-stroke oil and drive the vehicle home." It's an outdated fix for a separate issue. What petrol has weakened stays diluted, and that petrol remains in your tank anyway.
Myth: "Drain that tank yourself and you're sorted." After the motor has run, some of that petrol is no longer inside your tank: it is in your filter and the lines, and it goes straight back through your pump on your next start. And, a can of petrol filled at the roadside is truly hazardous.
How does petrol in a diesel take place?
Carelessness is rarely the cause, and no one means to do it. One way only, because of the nozzles: the slimmer petrol one slips inside a diesel filler with almost no resistance, while the diesel one generally won't fit a petrol vehicle. That is how the forecourt makes it easy.
Habit and your car getting out of step is when it occurs. Courtesy car, hire car, or a car that is new. One petrol and one diesel on the driveway of the same household. A forecourt you know, only with its pumps laid out differently. A rushed fill en route to Skegness with a train to catch. Years of petrol motors behind you, a diesel Volkswagen Golf in front of you on the forecourt for its first tank — that's when. Add rain, a phone call or a back seat full of kids, and your hand repeats what it has always done.
Next time you fill up in Seacroft: preventing petrol in a diesel
- A green handle for unleaded and black for diesel is usual in the UK — but not on each forecourt. Go by the label on the pump, not the colour.
- In a motor you do not know, look inside the flap over the filler or at the cap before your first fill: many cars print the fuel there.
- Good intentions do less than a sticker or a fob in a vivid colour on the diesel's key when a household has one of each. So mark it.
- "Diesel", out loud, before you lift the nozzle — every time a new or hired car needs its first tank. It sounds silly. It does the trick.
- While you're thinking about something else, this is an easy mistake to make — so tuck your phone away.
- Add-on devices are available for motors without one, and some diesels come with a filler that will not accept a petrol nozzle. Useful — but a safety net at best, never a reason to stop checking the label.
- Stop as soon as you realise. Less petrol in your tank means a thinner blend. It doesn't change what to do next, which is still not to crank it.
Already put petrol in a diesel around Seacroft?
The order of things is brief, then. Leave it unstarted, with the ignition switched off too. Still at the forecourt, at Tesco or anywhere else? Ask the staff to help you push the vehicle away from the pump. Then ring 0333 366 0103 and tell us what went in, about how much, and whether it has run.
If it was AdBlue and not petrol, say so. That's a separate fault — corrosion and deposits and not lost lubrication — and it has its own page for Seacroft.
What makes one Seacroft petrol in a diesel job cost more than the next
There is no honest single quote for this, because the four scenarios above are four different tasks. What moves the cost is chiefly which of them you're in. Next it's the share — how much petrol got in against how much that tank holds — and after that where the vehicle is and whether our van can reach it safely.
What was put in, how much, and if it has run — three questions our engineers ask before quoting, not after, for precisely that reason. Their answers are what turn a range into one firm number.
About Seacroft and its setting
Seacroft is a coastal suburban area in Lincolnshire, situated near the towns of Skegness and Wainfleet Clough. Seacroft lies at a low elevation of around 5 metres, close to the Bramble Hills and the Lincolnshire coastline. Seacroft has a population of approximately 3306 people, predominantly living in detached housing.
Fuel drain cover across Lincolnshire, Seacroft included
Seacroft rests in the PE postcode area, and the vans that answer petrol in diesel call-outs there work the places around it as well — Bramble Hills, Skegness and Wainfleet Clough among them. The vehicle doesn't need to come to us: we drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
At the petrol pump around Seacroft, right now?
Nothing beats it: that is where you are. Keep it off. Phone.