How Worried Should You Be? Petrol in a Diesel Car in Thrupp
Probably less than you are now — as long as no one has started it. "Have I wrecked it?" is the first thing everyone in Thrupp 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 driving. Petrol in Diesel is who to call, with the engine left off, and so it stays that way. The rest of this page explains what petrol really does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you again.
What petrol in a diesel does to your engine
Passing through a motor, diesel does two jobs at the same time. Lubricating comes before burning; it does both. Made to extremely fine clearances, the injectors and the pump rely on the diesel moving through them to stop their surfaces wearing against one another.
Petrol does the first job poorly and the second not at all. A pump running on a petrol mix is wearing itself out, since petrol is thinner than diesel and strips out the lubrication the fuel system depends on. Petrol is also made to resist igniting under compression — the opposite of what a diesel needs from its fuel — and that is where the clattering starts.
Put these together and the shape of the trouble is clear. The damage is done by circulation, not by contact. Petrol in the tank is a fuel problem. Whatever a worn pump sheds goes on, borne by your fuel, into the fuel injectors further along, which is why a pump that has been working on that petrol is where a mechanical fault begins.
Thrupp, petrol in a diesel: four cases, from mild to serious
Filled up, not once started. The best case there is. That petrol is inside that tank and only the tank, and the task is a drain and a flush where the car sits. This is the one situation that can only really take place on a forecourt, as anywhere else your car has been driven to get there.
Your ignition switched on, or a short start. Once primed, the fuel system has pulled petrol out of your tank as far as the fuel filter and the fuel lines. Normally little more than draining, flushing and sorting your filter, so still simple.
Driven a couple of miles. Now your pump has spent these miles working on weakened fuel. Miles is only half of that; how hard it was driven matters just as much. Either way this work includes that tank, the fuel lines, the filter and fresh fuel through the entire circuit. Driving the children to Thrupp School is one sort of trip. Getting as far as Gloucester, under 10 miles away, makes a very different task — as does any distance on the M5, under 10 miles from Thrupp, with the engine running hard the whole time.
Driven till it complained. Knocking, a ragged idle, smoke, a throttle that has gone soft. The motor is telling you the fuel is no longer acting like diesel. Whether it's the verge on Claypits Lane, a lay-by or a side street, stop where you are and leave it. Long-term damage is very rare if a vehicle is stopped early, and the fuel drain and flush that still come first sort it out.
Stories Thrupp motorists hear about petrol in a diesel
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It will not. Nothing comes out when you top up — that tank simply carries more of the same blend. Percentage isn't how a diesel fuel system copes with petrol, whatever that advice assumes.
Not so: a modern diesel copes with a bit of petrol. Rather, the reverse. Protection counts more on current diesels, not less, since their fuel runs through finer parts at higher pressure.
Myth: "If it starts and drives, there's no harm done." This is the one that catches people. Feed diesel to a petrol motor and it normally will not run, and so the motorist stops — and the damage stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually will; meanwhile your pump grinds. Being able to run isn't the same as being fine.
Myth: "Add some two-stroke oil and drive it home." It is an old workaround for a distinct issue. That petrol is still in your tank afterwards, and whatever it has weakened is not put back.
Once the engine has been run, part of that petrol sits in the fuel filter and the fuel lines, not the tank — and the next start sends it right back through the pump. So the myth "drain your tank yourself and you are sorted" doesn't hold. Also, a can of petrol drained by the roadside is truly risky.
Why petrol in a diesel occurs at all
On purpose? Never. Through carelessness? Seldom, if ever. A diesel nozzle mostly won't go into a petrol vehicle, yet the narrower petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error straightforward, and only in one direction.
When habit and your car stop matching, it occurs. A new vehicle, a hire car or a courtesy car. A household with one petrol and one diesel on the driveway. A forecourt you know, only with its pumps laid out differently. A rushed fill en route to Stroud with a train to catch. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is exactly the moment it happens. Add rain, a phone call or a back seat full of kids, and the hand repeats what it has always done.
Avoiding petrol in a diesel next time you fill up around Thrupp
- A green handle for unleaded and black for diesel is usual in the UK — but not on every forecourt. Go by the label on the pump, not the colour.
- Many motors state the fuel type inside your filler flap or on the cap, so check there on your first fill in a car you don't know.
- One of each in the household? Label your key to your diesel — a coloured fob, a sticker — since meaning to remember is not enough.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the pump. It sounds daft and it does the trick.
- Thinking about something else is when this becomes an easy mistake to make, so tuck the phone away and keep your mind on the pump.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler designed to block a petrol nozzle, and aftermarket devices are available for the rest. Treat it as a safety net, then keep reading the petrol pump.
- Less petrol means a thinner mix, and so stop as soon as you realise — while remembering that your next stage is unchanged. It is still not to fire it up.
Petrol already in a diesel in Thrupp? Begin here
Short and simple, then, is the order of things. Do not crank it, and don't turn the ignition on. Ask the staff to help you roll it away from the petrol pump if you are still at the forecourt, whether that is BP or somewhere else. Then ring 0333 366 0103 and tell us what got in, roughly how much, and if it's run.
If it was AdBlue instead of petrol, say so. That is a separate fault — corrosion and deposits rather than lost protection — and it has its own page for Thrupp.
One petrol in a diesel job around Thrupp costs more than another. Why?
Four separate tasks lie behind the four scenarios above — which is why there is no honest single quote. The situation itself does most of the work of moving the cost. Two things come after that: the petrol that went in as a proportion of what the tank takes, then the spot the car is in and whether a technician can get to it safely.
Ahead of any quote, not after, we ask three queries: the fuel that went in, its quantity, and if it's run. That's why. Those replies are what turn a range into one firm number.
About Thrupp and its setting
Thrupp is a village in Gloucestershire, situated on the banks of the River Frome at an elevation of around 88 metres. Thrupp lies near the city of Gloucester, approximately 9 miles to the west, and is surrounded by nearby places such as Bowbridge and Butterrow. Thrupp has a population of around 604 people, predominantly living in detached houses. Thrupp is located in the South West region of England, about 90 miles west of London.
Across Gloucestershire and in Thrupp: fuel drain cover
Thrupp rests in the GL postcode area, and our vans that answer petrol in diesel calls there work the places around it as well — Bowbridge, Butterrow and Mount Pleasant among them. No need to move your vehicle to us. Forecourts, supermarket car parks, lay-bys and your own drive are all places where we work.
At the petrol pump around Thrupp, right now?
Then you are in the best place there is. Keep the vehicle switched off, and ring.