How Wood: Petrol in a Diesel Car? How Worried to Be
Probably less than you already are — provided nobody has started the vehicle. "Have I ruined it?" is the first thing anyone around How Wood asks, and the truthful answer is generally no, since petrol resting in a diesel tank hurts nothing till it is drawn through your fuel system — by ignition priming, by your starter, or by driving. To keep the car that way, call Petrol in Diesel then leave the engine switched off. What petrol actually does to a diesel, how to judge how far it's gone, and how to keep it from happening a second time: that's the remainder of this page.
Inside your engine: what petrol in a diesel does
On its way through a motor, diesel does two tasks. It ignites, and before it burns it lubricates. Extremely fine gaps are built into the injectors and the high-pressure pump, and only the diesel flowing through stops their surfaces grinding together.
The second job petrol doesn't do at all, and the first it does poorly. The knocking comes from petrol being designed not to ignite when compressed, which is precisely the reverse of what a diesel needs. On top of that it is thinner than diesel, it strips out the protection the system depends on, and any pump working on such a mixture is wearing itself.
Seen together, they make clear the shape the trouble takes. The harm is done by circulation, not by contact. All a tank with petrol in it amounts to is a fuel issue. Once the pump has been running on that petrol, a mechanical problem has started: whatever is shed by a pump that's wearing is carried downstream to the fuel injectors with your fuel.
Petrol in a diesel in How Wood: how serious is it? Four cases
Filled up, and never started: nothing beats it. The petrol is inside your tank and just the tank, and the task is a drain and a flush where the vehicle sits. This is the one scenario that can only really happen on a forecourt, as anywhere else your car has been driven to get there.
Your ignition switched on, or a brief start. The fuel system has been bled, so petrol has left your tank and reached the fuel filter and the fuel lines. Still usually straightforward: drain, flush, and your filter sorted.
Driven a few miles. Now the pump has spent these miles working on weakened fuel. How hard the vehicle was driven counts as much as how far, and this work covers your tank, the fuel lines, the fuel filter and fresh fuel through the entire circuit. Short trips, such as the school run to How Wood Primary and Nursery School, are one matter. Any miles on the M25, under a mile from How Wood, means the motor has worked hard throughout, and a run to St Albans, under 3 miles away, makes a very different task too.
Driven until it protested. Knocking, a ragged idle, smoke, a throttle that has gone soft. The engine is telling you the fuel is no longer acting like diesel. Whether it's the verge on Penn Road, a lay-by or a side street, stop where you are then leave it. What comes first is still the drain and flush, and that takes care of it, with long-term damage very unusual if a car is stopped quickly.
Stories How Wood drivers hear about petrol in a diesel
Myth: topping up to full with diesel makes it fine. It does not. Nothing comes out when you top up — the tank simply carries more of the same blend. Percentage is not how a diesel fuel system tolerates petrol, whatever that advice supposes.
Not so: a newer diesel copes with a bit of petrol. If anything, the reverse. Smaller components and higher pressure are how a newer diesel runs its fuel, and that makes the lubrication count more, not less.
"It starts, it drives, and so there is no harm" — the myth that trips up most motorists than any other. The motorist of a petrol engine fed diesel usually stops, since it will not run, and the harm stops with them. Feed petrol to a diesel and it usually starts, ticks over and pulls away like nothing has happened — all while its pump wears. Fine and running are not the same thing.
Myth: a two-stroke additive lets you to drive home. It was an old fix, meant for another issue. It does not put back what petrol has thinned, and the petrol is still in that tank later.
Once your engine has run, part of the petrol is in the filter and the fuel lines, not the tank — and the next start sends it straight back through your pump. So the myth "drain your tank yourself and you are sorted" doesn't stand up. Also, a can of petrol drained by the roadside is truly hazardous.
How petrol ends up: petrol in a diesel
No one does it on purpose, and it's rarely carelessness. The forecourt makes it simple: the petrol nozzle is the narrower of the two, and it slides into a diesel filler with almost no resistance, whilst a diesel nozzle mostly won't go into a petrol vehicle at all. So the error runs one way.
It takes place when habit and the car stop matching. Hire cars, courtesy cars, and vehicles that are new to you. Households running one of each, petrol and diesel. Your normal forecourt, its pumps suddenly in a different order. Filling up in a hurry en route to the nearest station, with a train to catch. The first fill-up in a diesel Volkswagen Golf after years of driving petrol is exactly the moment it occurs. Your hand does what it has always done when you add rain, a phone call or a back seat full of children.
Preventing petrol in a diesel next time you fill up around How Wood
- Read the petrol pump, not the colour. In the UK unleaded handles are usually green and diesel black, but not on each forecourt. The label is what matters.
- Check your filler flap. Plenty of vehicles state the fuel inside the flap or on the cap. Look at it on the first fill in a motor you don't know.
- One of each in the household? Label the key to your diesel — a coloured fob, a sticker — because meaning to remember is not enough.
- Before the nozzle comes off the pump the first time you fuel a hired or new motor, say "diesel" out loud. Silly, perhaps, but it works.
- Mistakes like this are straightforward to make whilst your mind is on something else, and so your phone goes away.
- Add-on devices exist for motors without one, and some diesels come with a filler that will not take a petrol nozzle. Helpful — but a safety net at best, never a reason to stop checking the label.
- The moment you notice, stop: less petrol in the tank means a weaker blend. What to do next does not change, though — still don't start it.
Petrol already in a diesel around How Wood? Begin here
Then, there is just a short order of things. Leave it unstarted, with your ignition off too. The attendants on the forecourt — whether at Shell itself or wherever you filled up — will usually help push it away from the petrol pump if you ask. Next, 0333 366 0103. We'll ask what was put in, about how much, and if it has been run.
Say so if it was AdBlue instead of petrol: it is a separate issue, with its own page for How Wood, because AdBlue brings corrosion and deposits instead of lost lubrication.
What makes one How Wood petrol in a diesel task cost more than the next
The four situations above are four different tasks, so no single quote for this would be fair. Mostly, your cost shifts with which one you're in. Two things follow that: the petrol that was put in as a proportion of what your tank takes, then the place the vehicle is in and whether a technician can get to it safely.
Before any quote, not after, come three queries: the fuel that went in, the volume, and if it has run. That's why. Those answers change a range into a straight figure.
About How Wood itself
How Wood is a village in Hertfordshire, situated approximately 2.3 miles from St Albans and 17.5 miles from London. How Wood sits in a relatively low-lying area at around 86 metres above sea level, surrounded by other small settlements like Park Street and Chiswell Green. How Wood has a population of around 2286 people, predominantly living in semi-detached housing.
Across Hertfordshire and around How Wood: fuel drain cover
Petrol in diesel call-outs around How Wood — part of the AL postcode area — go to vans that likewise cover the places about it, Park Street, Frogmore and Chiswell Green 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 drive.
Still at the pump in How Wood?
Then you are in the best place there is. Keep it off. Phone.