Wellow: Petrol in a Diesel Car? How Worried to Be
If it hasn't been started, you can worry far less than you likely are. Until the ignition primes your pump, your starter turns, or the vehicle is driven, petrol in a diesel tank just rests there and does no harm. Which means the truthful reply to that first Wellow question — "have I wrecked it?" — usually no. Keep it like that: leave the motor off and ring Petrol in Diesel. The rest of this page covers what petrol actually does to a diesel, how to tell how far it has got, and how to make sure it does not happen to you again.
What petrol in a diesel does to the motor
Passing through an engine, diesel is doing two things at the same time. Before it combusts, it protects — then it ignites. Designed to extremely fine gaps, the injectors and your pump rely on your diesel flowing through them to keep their surfaces from wearing against one another.
Of those two tasks, petrol manages the first poorly and the second not at all. Being less viscous than diesel, petrol strips away the protection a fuel system needs, so a pump on the blend to wear itself. It's equally made to resist igniting under compression — the reverse of what a diesel needs — which is why you get the rattling.
Seen together, they show the shape the trouble takes. The damage is done by circulation, not by contact. All a tank with petrol in it amounts to is a fuel issue. A pump that has been running on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds moves on with the fuel to your injectors further on.
Wellow, petrol in a diesel: four cases, from mild to serious
Filled up, never started. The best case there is. Only your tank has petrol in it, and so the job is draining that tank and purging the fuel system where the car stands. This situation can only truly happen on a forecourt: anywhere else, the vehicle got there by being driven.
Ignition on, or started for a moment. Petrol has left the tank and reached the fuel filter and the fuel lines, because the system has been bled. Still generally easy: drain, flush, and your filter sorted.
Those few miles on the road meant the pump labouring on fuel diluted by petrol the whole way. How hard the vehicle was driven matters as much as how far, and this work covers that tank, your lines, your filter and clean fuel through the whole circuit. On the school run to St Julian's Church School, the miles is short. Driving as far as Bath, under 5 miles away, makes a very different job — as does any mileage on the M4, under 15 miles from Wellow, with the engine labouring hard all the way.
Clattering, a lumpy idle, smoke, a throttle gone soft: driven till it complained. That's your engine telling you its fuel no longer is acting like diesel. Whether it is the verge on Railway Lane, a lay-by or a side street, stop where you are then leave it. The drain and flush-through still go first, and they deal with it: when a vehicle is stopped early, long-term damage is very rare.
What Wellow drivers get told about petrol in a diesel — and the stories in it
False: topping up to full with diesel makes it fine. It does not. Topping up removes nothing; it gives you a bigger tank of the same mixture. That advice supposes a diesel fuel system tolerates petrol by percentage. It does not.
Myth: a newer diesel copes with a bit of petrol. If anything, the opposite. A newer diesel runs its fuel through finer components at higher pressure, which makes the lubrication count more, not less.
This is the one that catches motorists. Myth: "If it starts and drives, there's no harm done." Feed diesel to a petrol engine and it usually won't run, so the driver stops — and the damage 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 the pump wears. Running doesn't mean fine.
Myth: a two-stroke additive lets you to drive home. It is an old workaround, meant for another problem. That petrol is still in your tank afterwards, and what it has thinned isn't put back.
If your engine has run, part of that petrol sits in your filter and your lines, not that tank — and your next start sends it straight back through the pump. So the myth "drain the tank yourself and you are sorted" doesn't stand up. Also, a can of petrol drained at the kerbside is genuinely risky.
Petrol in a diesel: how does it take place?
A careless moment is seldom the cause, and nobody means to do it. The petrol nozzle is the smaller of the two and slides into a diesel filler with almost no resistance; a diesel nozzle generally will not go into a petrol motor at all. The forecourt makes it easy, and the error runs one way.
The moment routine stops matching the vehicle is the moment it takes place. Hire cars, courtesy cars, and cars that are new to you. A household with one petrol and one diesel on the drive. A well-known forecourt with the pumps in a different order. A hurried fill on the way to Freshford with a train to catch. Years of petrol motors behind you, a diesel Skoda Octavia in front of you at the forecourt for its first tank — that's when. With rain, a call arriving, or children to deal with, your hand simply does what it has always done.
How to prevent petrol in a diesel on your next fill-up in Wellow
- A green handle for unleaded and black for diesel is normal in the UK — yet not on every forecourt. Trust the label on the petrol pump, not the colour.
- The first fill in an unfamiliar car is the time to check the filler flap — on it, or on the cap, many cars state which fuel they take.
- Good intentions do less than a sticker or a fob in a vivid colour on your diesel's key if a household has one of each. So mark it.
- "Diesel", out loud, before you pick up the nozzle — every time a new or hired car needs its first tank. It sounds silly. It works.
- Whilst you are 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 come with a filler built to reject a petrol nozzle, and add-on devices are available for vehicles without one. They are a backstop, not a reason to stop checking the petrol pump.
- As soon as you notice, stop: less petrol inside that tank means a weaker mixture. What to do next doesn't change, though — still don't crank it.
Already put petrol in a diesel around Wellow?
Then, there's just a short order of things. Don't fire it up, and don't switch the ignition on. Ask the attendants to help you push it away from the pump if you're still at the forecourt, whether that is Esso or anywhere else. Next, 0333 366 0103. We'll ask what got in, roughly how much, and if it has been run.
Corrosion and deposits form the issue with AdBlue, whereas petrol brings lost lubrication. So if it was AdBlue, say so — and read its own Wellow page.
What makes one Wellow petrol in a diesel job cost more than the next
An honest single price does not exist here: four scenarios, four separate jobs. Mostly, the cost shifts with which situation you're in. Two things follow that: the petrol that got in as a share of what your tank holds, then the spot the car is in and whether a technician can get to it safely.
What was put in, how much, and if it has run — three queries our technicians ask before quoting, not after, for precisely that reason. Their answers are what turn a range into one firm number.
About Wellow itself
Wellow is a small village in Somerset, situated on the riverside in the South West of England, with a population of around 549 people. Wellow has a mix of old and new housing, but predominantly features detached homes, and is located near to several other small settlements, including Twinhoe and Combe Hay. Wellow sits at an elevation of 76 metres, close to the city of Bath, which is just 4.2 miles away. Wellow is also within easy reach of London, being around 97.7 miles to the west of the capital.
Fuel drain cover across Somerset, Wellow included
Petrol in diesel calls in Wellow — part of the BA postcode area — go to vans that likewise cover the spots round it, Twinhoe, Upper Baggeridge and Combe Hay among them. We drain where your vehicle is — your own drive, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
In Wellow and still at the pump?
The best position there is, then — that is where you are. Call, and leave it switched off.