How Worried Should You Be? Petrol in a Diesel Car in Pantmawr
Less than you probably are, if it hasn't been started. "Have I ruined it?" is the first question anyone in Pantmawr asks, and the honest answer is normally no, because petrol left in a diesel tank harms nothing until it is drawn through the fuel system — by ignition priming, by the starter, or by being driven. Keep it that way: leave the engine off then phone Petrol in Diesel. What petrol really does to a diesel, how to judge how far it has travelled, and how to keep it from happening again: that's the rest of this page.
The motor and petrol in a diesel: what happens
On its way through a motor, diesel has two jobs. Lubricating comes before burning; it does both. Extremely fine clearances go into your injectors and your high-pressure pump, and only your diesel flowing through keeps those surfaces from grinding together.
Badly at the first, not at all at the second: that is petrol. Being less viscous than diesel, petrol strips out the lubrication a fuel system needs, so a pump on that mixture wearing itself. It's equally made to resist igniting under compression — the reverse of what a diesel needs — which is where you get the clattering.
Put these together and the shape of the problem is clear. Contact doesn't do the harm — circulation does. Any tank with petrol in it is a fuel issue. Once your pump has been running on that petrol, a mechanical issue has begun: anything shed by a pump that's wearing down travels downstream to your injectors with your fuel.
How serious is petrol in a diesel? Four scenarios our technicians see around Pantmawr
The best case there is: filled up, not once started. Being at a forecourt is what makes this the case: elsewhere, the car has been driven there to begin with. With the petrol kept in that tank alone, it is drained and flushed right where it stands, and nothing more is needed.
Started for a moment, or just the ignition on. Petrol has come out of that tank and got to the fuel filter and your lines, because the system has been primed. Normally little more than draining, cleaning and sorting your filter, and so still easy.
Some miles driven, and your pump has spent each of them running on weakened fuel. Tank, lines, filter, then clean fuel run through the entire system: that's this work, and the way the vehicle was driven counts as much as the mileage. The school run to the local primary school is one thing. Any miles on the M4, under a mile from Pantmawr, means the engine has worked hard throughout, and a run to Cardiff, under 5 miles away, is a very different task too.
Driven on till it protested — rattling, smoke, a lumpy idle, a dead throttle. The engine is telling you your fuel is no longer behaving like diesel. Whether it is the verge on Caer Wenallt, a lay-by or a side road, stop where you are and leave it. What goes first is still the fuel drain and flush, and that sorts it out, with lasting damage very rare if a vehicle is stopped soon.
Petrol in a diesel stories Pantmawr people hear
False: topping up to full with diesel makes it fine. It doesn't. A bigger tank of the same mix is all it gives, since topping up removes nothing. That guidance presumes a diesel fuel system tolerates petrol by percentage. It doesn't.
Myth: "A newer diesel can cope with a bit of petrol." If anything, the opposite. Protection counts more on current diesels, not less, because their fuel runs through more precise components at higher pressure.
"It starts, it drives, so there is no harm" — the myth that trips up more motorists than any other. Any petrol motor fed diesel normally won't run, and so the driver stops and the harm stops with them. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile your pump grinds. Fine and running aren't the same at all.
An old fix for a different problem is behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." It does not put back what petrol has diluted, and that petrol is still in that tank later on.
If the motor has run, part of that petrol sits in the filter and your lines, not the tank — and your next start sends it straight back through the pump. So the myth "drain the tank yourself and you're sorted" does not hold. Draining petrol into a can at the kerbside is also really risky.
How does petrol in a diesel happen?
On purpose? Never. Through carelessness? Seldom, if ever. One way only, because of the nozzles: the smaller petrol one slips inside a diesel filler with almost no resistance, while the diesel one mostly will not fit a petrol vehicle. That is how the forecourt makes it easy.
It happens when habit and the vehicle stop matching. Hire cars, courtesy cars, and cars that are new to you. One petrol and one diesel on the driveway of the same household. The pumps in a different order on a well-known forecourt. Rushing for a train outside Coryton and fuelling up en route. Years of petrol cars behind you, a diesel Volkswagen Golf in front of you at the forecourt for its first tank — that is when. Your hand does what it has always done when you add rain, a phone call or a back seat full of children.
Next time you fill up in Pantmawr: preventing petrol in a diesel
- Green for unleaded and black for diesel is usual in the UK — yet not on each forecourt. Go by the label on the petrol pump, not the colour.
- Plenty of cars state the fuel type inside your filler flap or on the cap, and so check it on the first fill in a car you don't know.
- Good intentions do less than a sticker or a fob in a bright colour on your diesel's key if a household has one of each. So label it.
- It seems daft and it works: on the first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the pump.
- Put the phone away. This is an easy mistake to make while you are thinking about something else.
- Some diesels come with a filler built to block a petrol nozzle, and devices you can add exist for cars 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 thinner mixture results from less petrol in your tank, yet the next step stays the same: do not fire it up.
Put petrol in a diesel in Pantmawr already?
Then the order of things is short. Never crank it, and don't turn the ignition on. The attendants on the forecourt — whether at Asda itself or wherever you filled up — will normally help push it clear of the petrol pump if you ask. Phone 0333 366 0103 next, with three answers — your fuel, the approximate quantity, and whether it has run.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost lubrication, make it a different problem — Pantmawr has a page all for it.
Pantmawr petrol in a diesel jobs: why one costs more than another
The four situations above are four separate jobs, so no single quote for this would be honest. What shifts the cost is mostly which of them you are in. Next it is the share — how much petrol was put in against how much that tank holds — and then where the vehicle is and whether our van can reach it safely.
That's why we ask three queries before pricing rather than after: what went in, how much, and if it has run. With those replies, there is a straight figure rather than a range.
About Pantmawr and its setting
Pantmawr is a suburban area in Cardiff, situated near the River Taff and close to the city centre. Pantmawr has a mix of housing types, but semi-detached homes are predominant in the area. Pantmawr is located near several other suburbs, including Coryton, Rhiwbina, and Whitchurch, and is about 3.9 miles from Cardiff city centre.
Pantmawr and Cardiff: where our fuel drain cover runs
Pantmawr sits in the CF postcode area, and the teams that answer petrol in diesel call-outs there work the locations near it as well — Coryton, Rhiwbina and Whitchurch among them. The vehicle doesn't need to come to us: our technicians drain at a forecourt, in a supermarket car park, in a lay-by or on your own drive.
Pantmawr: still at the petrol pump?
Then, you could not be in a better place. Switched off it stays; then ring.