How Worried Should You Be? Petrol in a Diesel Car in St Johns
Far less than you probably are, provided it hasn't been started. "Have I wrecked it?" is the first question anyone around St Johns asks, and the truthful answer is usually no, since petrol left in a diesel tank harms nothing till it is dragged through the fuel system — by ignition priming, by the starter, or by driving. Petrol in Diesel is who to call, with the motor left off, and so it remains that way. The remainder of this page explains what petrol actually does to a diesel, how to judge how far it has got, and how to make sure it doesn't happen to you again.
Inside your engine: what petrol in a diesel really does
Two jobs fall to diesel on its journey through a motor. It combusts, and before it combusts it lubricates. Very fine clearances are built into the injectors and your high-pressure pump, and only the diesel flowing through keeps their surfaces from grinding together.
Petrol handles the first job badly and the second not at all. It is thinner than diesel and takes away the protection the system depends on, and so a pump running on a petrol blend is a pump wearing itself. And petrol is designed to resist igniting under compression, which is the opposite of what a diesel needs from its fuel. That is where the rattling comes from.
Put these together and the shape of the problem is clear. The damage is done by circulation, not by contact. A tank with petrol in it is a fuel fault. The beginning of a mechanical one is a pump that has been running on that petrol — and whatever a worn pump sheds moves on with the fuel to your injectors downstream.
How bad is petrol in a diesel? Four scenarios our technicians see around St Johns
Filled but never started — as good as it gets. Only that tank has petrol in it, so the job is draining the tank and flushing the fuel system where your car sits. This situation can only really occur on a forecourt: anywhere else, the vehicle got there by being driven.
Started for a second, or only the ignition on. With your system primed, your lines and filter now hold petrol that came from your tank. Still generally straightforward: drain, flush, and your filter seen to.
Those few miles driven meant the pump labouring on fuel diluted by petrol the whole way. Tank, lines, filter, then clean fuel put through the entire system: that is the work, and the way your car was driven matters as much as the distance. The school run to Our Lady Queen of Peace Catholic Primary is one matter. A run as far as Worcester, under a mile away, is a very different job. So is any distance on the M5, under 3 miles from St Johns, where your engine has been labouring hard the whole time.
Rattling, an uneven idle, smoke, a throttle gone soft: driven until it complained. What you are hearing is the engine signalling fuel that no longer acts like diesel. Stop wherever you are — the verge on Bromyard Road, a lay-by, a side street — and leave the car there. Permanent damage is very rare if a vehicle is pulled over quickly, and the fuel drain and flush-through that still come first sort it out.
Myths St Johns drivers hear about petrol in a diesel
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. A bigger tank of the same mix is all you get, since topping up takes out nothing. That advice assumes a diesel fuel system tolerates petrol by percentage. It doesn't.
If anything, the opposite is true. Myth: "A modern diesel can cope with a bit of petrol." Protection matters more on modern diesels, not less, since their fuel passes through finer components at higher pressure.
This is the one that fools drivers. Myth: "If it starts and drives, there's no damage done." Feed diesel to a petrol engine and it normally will not run, and so the driver stops — and the damage stops with them. While your pump grinds, a diesel fed petrol normally starts, idles and drives away as if nothing has happened. Running isn't the same as fine.
"A drop of two-stroke oil and drive it home" — a myth, taken from a fix from years ago, for a different issue. The petrol is still inside your tank afterwards, and whatever it has weakened isn't put back.
The next start sends petrol back round your pump out of your lines and your filter, where some of that sits after the motor has run. That is why draining your tank yourself does not leave you sorted — a myth. And, a can of petrol drained at the roadside is genuinely dangerous.
How petrol ends up: petrol in a diesel
It is seldom carelessness, and no one does it on purpose. One way only, because of the nozzles: the narrower petrol one slips inside a diesel filler with almost no resistance, whereas the diesel one generally will not fit a petrol vehicle. That is how the forecourt makes it simple.
It happens when routine and the vehicle stop matching. Courtesy car, hire car, or a motor that is new. Households running one of each, petrol and diesel. A familiar forecourt with the pumps in a different order. Rushing for a train at Worcester Foregate Street and fuelling up en route. A new-to-you diesel Skoda Octavia, its first fuelling, and a motorist accustomed to petrol: precisely when it happens. Throw in a back seat full of kids, a phone call or rain, and habit takes over.
St Johns drivers: how to prevent petrol in a diesel next time
- The label is what counts, so check the petrol pump rather than the colour: in the UK unleaded handles are normally green and diesel black, yet not on every forecourt.
- Many vehicles state the fuel type inside the filler flap or on the cap, so check it on the first fill in a car you do not know.
- Good intentions do less than a sticker or a fob in a vivid colour on your diesel's key if a home has one of each. So label it.
- It sounds silly and it does the trick: on your first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the pump.
- Tuck the phone away. This is an easy mistake to make while you're thinking about something else.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler built to block a petrol nozzle, and aftermarket devices exist for the remainder. Treat it as a safety net, and keep checking the pump.
- Less petrol makes a thinner mix, and so stop as soon as you notice — though remembering that the next stage is unchanged. It is still not to crank it.
Put petrol in a diesel in St Johns already?
The order of things is short, then. Starting it is out, and so is switching on the ignition. Ask the staff to help you push it away from the petrol pump if you're still at the forecourt, whether that's Esso or anywhere else. Then phone 0333 366 0103 and tell us what went in, about how much, and if it's run.
If it was AdBlue and not petrol, say so. That's a different issue — corrosion and deposits rather than lost lubrication — and it has its own page for St Johns.
What makes one St Johns petrol in a diesel job cost more than the next
The four scenarios above are four separate tasks, so no single price for this would be fair. What shifts your cost is mostly which of them you're in. Where your car is counts too, and whether a van can safely reach it, after the share of petrol to what your tank holds.
That's why our technicians ask three questions before costing instead of after: what went in, how much, and if it has run. With the answers, there is a straight figure instead of a range.
About St Johns
St Johns is a suburban area located on the riverside in Worcestershire, with a mix of terraced housing and other residential properties. St Johns sits near the city of Worcester, at an elevation of around 27 metres, and is close to nearby places such as Diglis and Wick Episcopi. St Johns is situated within the West Midlands region, approximately 101.5 miles from London. St Johns has a population of around 5711 people, according to recent estimates.
St Johns and Worcestershire: where our fuel drain cover runs
Our vans answering petrol in diesel calls in St Johns, in the WR postcode area, equally work the places around it, Diglis, Worcester and Wick Episcopi included. You need not bring the car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all locations we drain.
St Johns: still at the petrol pump?
In that case, you could not be in a better position. Switched off it stays; then ring.