How Worried Should You Be? Petrol in a Diesel Car in St Johns
Not started? Then less anxious than you probably are. Everyone around St Johns begins with "have I wrecked it?", and the honest answer is usually no: petrol resting in the tank of a diesel stays harmless until priming, cranking or driving pulls it into your fuel system. Leave your motor off then call Petrol in Diesel — that is how you keep it like that. What petrol actually does to a diesel, how to gauge how far it has travelled, and how to stop it from happening again: that's the rest of this page.
Petrol in a diesel: what does it do to the motor?
Passing through an engine, diesel is doing two things at the same time. It ignites, and before it ignites it protects. Designed to very fine tolerances, the injectors and the pump rely on the diesel flowing through them to stop their surfaces wearing against one another.
Petrol does the first task badly and the second not at all. It's runnier than diesel and strips away the lubrication your fuel system hinges on, and so a pump running on a petrol mixture 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's where the knocking comes from.
The shape of the problem is plain once you put those together. The damage is done by circulation, not by contact. Petrol in a tank is a fuel fault. Whatever a worn pump sheds goes on, borne by your fuel, into your injectors further along, which is why a pump that has worked on that petrol is where a mechanical problem begins.
Petrol in a diesel in St Johns: how serious is it? Four situations
The best case there is: filled up, not once started. At a forecourt, and genuinely only there, that petrol is still limited to the tank — because anywhere else the car was driven to get to it. The task is draining and cleaning on the spot.
Ignition on, or started for a moment. Your system has been bled, and so petrol has left that tank and got to the fuel filter and your lines. Drain, flush, see to your filter: still usually easy.
Driven a couple of miles. Now the pump has spent these miles labouring on weakened fuel. How hard your car was driven matters as much as how far, and this work takes in the tank, the lines, your filter and clean fuel through the whole system. Driving the children to St John's Church of England First School, Wimborne is one sort of trip. A run as far as Salisbury, under 25 miles away, is a very different task. So is any miles on the M27, under 25 miles from St Johns, where your engine has been running hard the whole time.
Rattling, a ragged idle, smoke, a throttle gone soft: driven until it complained. That is your motor telling you its fuel no longer is behaving like diesel. Pull up where you are — on the verge on Leigh Road, at the kerb, down a side road — and don't move it again. What goes first is still the drain and flush, and that sorts it out, with lasting damage very unusual if a car is stopped early.
Petrol in a diesel myths St Johns drivers hear
"Top it up the rest of the way with diesel and it will be fine" — a myth. It will not. Nothing comes out when you top up — that tank simply holds more of the same blend. A diesel fuel system doesn't tolerate petrol by percentage in the way that guidance assumes.
If anything, the reverse holds. Myth: "A modern diesel can cope with a bit of petrol." Smaller parts and higher pressure are how a current diesel runs its fuel, and that makes the protection count more, not less.
Myth: "If it starts and drives, there's no harm done." This is the one that fools motorists. The motorist of a petrol engine fed diesel normally stops, since it will not run, and the harm stops there. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually will; meanwhile your pump wears. A running engine doesn't mean fine.
An old workaround for a separate problem lies behind this one. Myth: "Add some two-stroke oil and drive it home." That petrol is still in your tank after that, and what it has thinned isn't put back.
"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 right back through your pump on the next start. It's also really risky to drain petrol into a can by the roadside.
How it happens: petrol in a diesel
On purpose? Never. Through carelessness? Rarely, if ever. One way only, since of the nozzles: the smaller petrol one slips inside a diesel filler with almost no resistance, whereas the diesel one mostly won't fit a petrol vehicle. That is how the forecourt makes it easy.
It occurs when routine and the car stop matching. Hire cars, courtesy cars, and vehicles that are new to you. Two motors on one driveway, one petrol, one diesel. The pumps in a different order on a well-known forecourt. Fuelling up in a hurry on the way to Hamworthy, with a train to catch. Years of petrol vehicles behind you, a diesel Volkswagen Golf in front of you at the forecourt for its first tank — that is when. With rain, a call arriving, or children to deal with, the hand just does what it has always done.
How to avoid petrol in a diesel on your next fill-up in St Johns
- Not every forecourt in the UK follows green for unleaded and black for diesel, even if most generally do. Read the pump's label; the colour is just a hint.
- Inspect your filler flap. Plenty of motors state the fuel inside the flap or on the cap. Look at it on your first fill in a vehicle you don't know.
- One of each in the home? Mark the key to the diesel — a coloured fob, a sticker — because meaning to remember is not enough.
- It sounds silly and it works: on your first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the petrol 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 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 exist for motors without one. They are a safety net, not a reason to stop checking the petrol pump.
- Noticing it mid-fill? Stop there and then. A weaker blend results from less petrol in your tank, but your next step remains the same: don't crank it.
Put petrol in a diesel around St Johns already?
Short and simple, then, is the order of things. Don't start it, and don't turn the ignition on. Ask the attendants to help you push it clear of the petrol pump if you are still on the forecourt, whether that's BP or anywhere else. What was put in, about how much, and whether it has run: tell us that when you phone 0333 366 0103.
Corrosion and deposits form the problem with AdBlue, where petrol means lost lubrication. So if it was AdBlue, say so — and read its own St Johns page.
One petrol in a diesel job in St Johns costs more than another. Why?
The four scenarios above are four separate jobs, so no single price for this would be honest. Mostly, the cost shifts with which one you are in. Where your car is counts too, and whether a van can safely get to it, after the ratio of petrol to what that tank holds.
Three questions come first, before any quote, instead of after — what got in, how much, has it run — and that is the reason. With the replies, you get a straight figure rather than a range.
About St Johns and its setting
St Johns is a suburban area in Dorset, situated on the riverside at a low elevation of 19 metres. St Johns is located near several nearby places, including Rowlands, East Brook, and Wimborne Minster, and is approximately 20 miles from the city of Salisbury. St Johns has a population of around 5697 people and predominantly consists of flat housing. St Johns is also within commuting distance to larger cities, with London being around 94 miles away.
St Johns and Dorset: where our fuel drain cover runs
St Johns waits in the BH postcode area, and our vans that answer petrol in diesel call-outs there work the spots around it as well — Rowlands, East Brook and Wimborne Minster among them. The vehicle does not need to come to us: we drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
Still at the pump in St Johns?
Then, you couldn't be in a better place. Call, and leave it turned off.