Petrol in a Diesel Car in Old Coulsdon: How Worried Should You Be?
Likely less than you are now — provided nobody has started it. "Have I ruined it?" is the first thing everyone in Old Coulsdon asks, and the truthful answer is normally no, because petrol left in a diesel tank hurts nothing till it's dragged through your fuel system — by ignition priming, by your starter, or by driving. To leave the car that way, call Petrol in Diesel then leave the engine alone. The remainder of this page covers what petrol actually does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you a second time.
Petrol in a diesel: what does it do to the engine?
Passing through a motor, diesel does two jobs at the same time. It protects first, and only then does it burn. Extremely fine tolerances are built into the fuel injectors and the high-pressure pump, and only the diesel running through keeps their surfaces from grinding together.
The second task petrol doesn't do at all, and the first it does badly. A pump running on a petrol mix is wearing itself out, since petrol is thinner than diesel and takes away the protection your fuel system depends on. Petrol is also designed to resist igniting under compression — the reverse of what a diesel needs from its fuel — and that is where the clattering comes.
Combined, those leave the shape of the problem plain. Not contact but movement is what does the damage. Any tank with petrol in it 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.
Old Coulsdon, petrol in a diesel: four situations, from mild to serious
Fuelled up, never started. The best case there can be. That petrol is inside that tank and only your tank, and the task is a drain and a flush where the vehicle stands. This is the one scenario that can only truly take place on a forecourt, as anywhere else your car has been driven to get there.
A moment's running, or just the ignition on. With your system primed, the fuel lines and filter now hold petrol that came from your tank. That is generally still a simple task — a drain, a flush, and the filter seen to.
A couple of miles driven, and your pump has spent every one of them labouring on thinned fuel. How hard your car was driven counts as much as how far, and this work covers the tank, the lines, the filter and fresh fuel through the entire circuit. Driving the children to Keston Primary School is one kind of trip. Driving as far as Westminster, under 15 miles away, makes a very different job — as does any distance on the M23, under 3 miles from Old Coulsdon, with your engine running hard all the way.
Driven until it protested. Clattering, a ragged idle, smoke, a throttle that has gone soft. The fuel isn't behaving like diesel any more, and your engine is saying so. Leave it wherever it has stopped: a lay-by, a side street, the verge on Tollers Lane. Long-term damage is very rare if a car is stopped soon, and the fuel drain and flush-through that still go first deal with it.
Stories Old Coulsdon motorists hear about petrol in a diesel
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Nothing is removed when you top up — your tank simply holds more of the same blend. The idea behind the advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
If anything, the reverse is true. Myth: "A current diesel can cope with a bit of petrol." 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, so no harm done" — the myth that catches most motorists than any other. The motorist of a petrol motor fed diesel normally stops, because it will not run, and the damage stops there. While your pump grinds, a diesel fed petrol usually starts, ticks over and drives away as though nothing has happened. Running isn't the same as fine.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a distinct fault. That petrol is still in your tank after that, and whatever it has weakened is not put back.
If the motor has been run, part of that petrol sits in your filter and the fuel lines, not that tank — and your next start pulls it right back through the pump. So the myth "drain the tank yourself and you are sorted" does not stand up. And, a can of petrol drained by the kerbside is genuinely risky.
How it happens: petrol in a diesel
No one does it on purpose, and it is rarely carelessness. The forecourt makes it easy: 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 slip runs one way.
It occurs when routine and the car stop matching. A new car, a hire car or a courtesy car. Households running one of each, petrol and diesel. A well-known forecourt with the pumps in a different order. A rushed fill on the way to Coulsdon South with a train to catch. Precisely the moment it occurs: after years of driving petrol, someone fills a diesel Volkswagen Golf for the first time. With rain, a call coming in, or children to deal with, the hand just does what it always has.
How to prevent petrol in a diesel on your next fill-up around Old Coulsdon
- Read the petrol pump, not the colour. In the UK unleaded handles are usually green and diesel black, yet not on each forecourt. The label is what matters.
- The first fill in a new vehicle is the time to check your filler flap — inside it, or on the cap, many vehicles state which fuel to use.
- Good intentions do less than a sticker or a fob in a bright colour on your diesel's key if a house has one of each. So label it.
- It seems daft and it works: on the first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the petrol pump.
- Put your phone away. This is an easy mistake to make whilst you're thinking about something else.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler built to refuse a petrol nozzle, and add-on devices are available for the remainder. Count it as a backstop, and keep reading the pump.
- Less petrol means a thinner blend, so stop as soon as you notice — while remembering that the next stage is unchanged. It's still not to fire it up.
Put petrol in a diesel in Old Coulsdon already?
The order of things is short, then. Do not turn the ignition on, and don't fire it up. If you're still at the forecourt — Shell or anywhere else — ask the attendants to help you roll it clear of the petrol pump. Next, 0333 366 0103. We will ask what got in, roughly how much, and if it's been run.
Corrosion and deposits are the problem with AdBlue, where petrol means lost protection. So if it was AdBlue, say so — and see its own Old Coulsdon page.
Why one petrol in a diesel task in Old Coulsdon costs more than another
Four different tasks lie behind the four situations above — which is why there is no honest single quote. Chiefly, the cost shifts with which situation you are in. Where your car is counts too, and whether our van can safely reach it, after the share of petrol to what the tank holds.
Before any quote, not after, come three questions: your fuel that went in, the amount, and whether it has run. That is why. Those replies are what change a range into one firm number.
About Old Coulsdon
Old Coulsdon is a suburban area in south London, situated approximately 14 miles from central London and near the North Downs. Old Coulsdon has a mix of housing types, but semi-detached homes are predominant, and it is close to nearby places like Kenley and Chaldon. Old Coulsdon sits at an elevation of around 167 metres, giving it a relatively high vantage point in the area. Old Coulsdon is also near Netherne on-the-Hill, another local community.
Old Coulsdon and Greater London: where our fuel drain cover reaches
The teams answering petrol in diesel calls in Old Coulsdon, in the CR postcode area, equally work the places near it, Kenley, Netherne on-the-Hill and Chaldon among them. We drain wherever the vehicle is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it never needs to come to us.
At the pump around Old Coulsdon, right now?
Then you are in the best place there can be. Ring, and leave it switched off.