Corston: Petrol in a Diesel Car? How Worried to Be
Provided it hasn't been started, you can worry less than you likely are. Everyone in Corston starts with "have I ruined it?", and the honest answer is usually no: petrol left inside the tank of any diesel stays harmless until priming, cranking or driving pulls it into the fuel system. Leave your motor off and ring Petrol in Diesel — that is how you keep it like that. Keep reading for three things: the effect petrol has inside a diesel motor, the clues of how far it has got, and the way to make sure you don't do it again.
The engine and petrol in a diesel: what happens
Two tasks fall to diesel on its journey through a motor. It protects to begin with, and only then does it burn. Your high-pressure pump and the fuel injectors are made to extremely fine gaps, and the diesel passing through them is what stops those surfaces from wearing against each other.
Poorly at the first, not at all at the second: that's petrol. A pump running on a petrol blend is wearing itself out, since petrol is thinner than diesel and takes away the lubrication the fuel system depends on. Petrol is also made to resist igniting under compression — the opposite of what a diesel wants from its fuel — and that is where any rattling starts.
The shape of the issue is clear when you put those together. Not contact but movement is what causes the harm. A tank with petrol in it is a fuel issue. A pump that has been labouring on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds moves on with the fuel to the fuel injectors further on.
Corston, petrol in a diesel: four situations, from mild to serious
Filled up, and never started: no case is better. Being on a forecourt is what makes this possible: elsewhere, the vehicle has been driven there to begin with. With the petrol kept in that tank alone, it is emptied and rinsed on the spot, and nothing more is needed.
A moment's running, or just the ignition on. Petrol has left your tank and reached the fuel filter and your lines, since the fuel system has been primed. That is normally still an easy job — a drain, a flush, and the filter seen to.
Those few miles driven meant the pump working on fuel diluted by petrol the whole way. The work is the tank, the lines, the fuel filter and fresh fuel through the entire circuit, and how hard your car was driven counts as much as how far. Short trips, like the school run to Saltford CofE Primary School, are one matter. Any distance on the M4, under 10 miles from Corston, means the motor has worked hard throughout, and a run to Bath, under 5 miles away, makes a very different job too.
It complained, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone uneven. The motor is telling you your fuel is no longer acting like diesel. Stop on the spot — on the verge on Corston Lane, at the kerb, down a side road — and do not move it again. Long-term damage is very unusual if a car is pulled over quickly, and the drain and flush that still come first take care of it.
Corston motorists and that petrol in a diesel stories they hear
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Nothing comes out when you top up — that tank just carries more of the same mixture. A diesel fuel system doesn't tolerate petrol by percentage in the way that guidance presumes.
Not so: a newer diesel copes with a bit of petrol. Rather, the opposite. A modern diesel runs its fuel through smaller parts at higher pressure, which makes the protection matter more, not less.
Myth: "If it starts and drives, there is no harm done." This is the one that catches drivers. Feed diesel to a petrol engine and it normally won't run, so the driver stops — and the harm stops with them. A diesel fed petrol usually starts, idles and drives away as though nothing has happened, while your pump grinds. A running engine doesn't mean fine.
Myth: "Add some two-stroke oil and drive the car home." It is an outdated fix for a different problem. It doesn't put back what petrol has weakened, and the petrol is still in your tank later.
Once your engine has been run, part of that petrol is in the filter and the lines, not your tank — and the next start sends it right back through your pump. So the myth "drain your tank yourself and you are sorted" does not stand up. Clearing petrol into a can at the kerbside is also genuinely dangerous.
Why petrol in a diesel happens so easily
No one does it on purpose, and it's rarely carelessness. A diesel nozzle mostly will not fit a petrol car, yet the smaller petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake easy, and just in that direction.
It occurs when habit and the vehicle stop matching. Courtesy car, hire car, or a vehicle that's brand new. A household with one petrol and one diesel on the driveway. A forecourt you know, only with its pumps arranged differently. Fuelling up in a hurry en route to Oldfield Park, with a train to catch. A new-to-you diesel Volkswagen Tiguan, its first fuelling, and a motorist accustomed to petrol: precisely when it happens. Add a back seat full of kids, a phone call or rain, and habit wins.
Preventing petrol in a diesel next time you fill up in Corston
- Not every forecourt in the UK follows green for unleaded and black for diesel, though most generally do. Read the petrol pump's label; the colour is just a hint.
- The first fill in a new vehicle is the time to check the filler flap — inside it, or on the cap, plenty of vehicles state the fuel to use.
- Mark your key. In a home with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of meaning to remember.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the petrol pump. It seems silly and it does the trick.
- Whilst you're thinking about something else, this is an easy mistake to make — so put the phone away.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler built to reject a petrol nozzle, and add-on devices are available for vehicles without one. They are a safety net, not a reason to stop reading the petrol pump.
- Stop the moment you notice. Less petrol in the tank makes a weaker blend. It doesn't change what to do next, which is still not to fire it up.
Petrol already in a diesel in Corston? Begin here
In that case, there's only a short order of things. Do not fire it up, and don't switch your ignition on. Ask the attendants to help you push it clear of the pump if you are still on the forecourt, whether that's Gulf or somewhere else. What was put in, about how much, and whether it's run: tell us that when you ring 0333 366 0103.
If it was AdBlue and not petrol, say so. That is a different problem — corrosion and deposits and not lost lubrication — and it has its own page for Corston.
Why one petrol in a diesel job in Corston costs more than another
There is no honest single price for this, because the four scenarios above are four different tasks. The situation itself does most of the work of moving your cost. The share matters next, meaning how much of the tank is petrol, and then the position of your car and whether reaching it is safe for our van.
That's why our technicians ask three questions before quoting instead of after: what went in, how much, and whether it's run. With the replies, you get a straight figure instead of a range.
About Corston and its setting
Corston is a small village in Somerset, situated on the banks of the River Avon at an elevation of around 44 metres. Corston lies close to the city of Bath, approximately 3.5 miles to the east, and is surrounded by nearby places such as Newton St Loe and Kelston. Corston has a population of around 502 people and is characterised by predominantly detached housing. Corston is located in the South West region of England, about 99.9 miles west of London.
Corston and Somerset: where our fuel drain cover reaches
Corston rests in the BA postcode area, and our vans that answer petrol in diesel jobs there work the spots around it as well — Newton St Loe, Clays End and Kelston among them. You need not move your vehicle to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all locations we drain.
In Corston and still at the petrol pump?
Then you are in the best spot there is. Keep it off. Ring.