Wimbledon: Petrol in a Diesel Car? How Worried to Be
Not started? Then less anxious than you probably feel. "Have I wrecked it?" is the first thing everyone around Wimbledon asks, and the honest answer is generally no, since petrol resting in a diesel tank hurts nothing till it's dragged through the system — by ignition priming, by the starter, or by being driven. Leave your engine off and call Petrol in Diesel — that is how you keep it like that. Read on for three things: the effect petrol has inside a diesel engine, the clues of how far it has got, and ways to make sure you never do it again.
Inside the engine: what petrol in a diesel does
Passing through an engine, diesel does two things at once. It lubricates to begin with, and only then does it burn. What keeps the surfaces inside the high-pressure fuel pump and the fuel injectors from wearing against one another is the diesel flowing through them — they are designed to extremely fine clearances.
Of those two jobs, petrol manages the first badly and the second not at all. Being less viscous than diesel, petrol strips out the lubrication a fuel system needs, leaving a pump on that mixture wearing itself. It is also made to resist igniting under compression — the reverse of what a diesel needs — which is where you get the rattling.
The shape of the issue is plain when you put those together. It's movement that causes the damage, not contact. All a tank with petrol in it amounts to is a fuel problem. The start of a mechanical one is a pump that has been running on that petrol — and whatever a worn pump sheds travels on with your fuel to the injectors downstream.
How bad is petrol in a diesel? Four scenarios we see in Wimbledon
The best case there can be: filled up, not once started. Just that tank has petrol in it, so the task is emptying that tank and purging the fuel system where the car sits. This scenario can only really occur at a forecourt: anywhere else, the car got there by being driven.
Ignition on, or started for a moment. Petrol has come out of the tank and reached your filter and the lines, since the system has been bled. Usually nothing more than draining, purging and seeing to the fuel filter, and so still straightforward.
Those few miles driven meant the pump working on fuel thinned by petrol the whole way. How hard the vehicle was driven counts as much as how far, and this work covers your tank, the lines, the filter and fresh fuel through the whole system. The school run to St Mary's Catholic Primary School is one thing. Getting as far as Westminster, under 10 miles away, makes a very different job — as does any miles on the M4, under 10 miles from Wimbledon, with your engine working hard all the way.
Driven until it complained. Clattering, a lumpy idle, smoke, a throttle that has gone soft. What you are hearing is your motor reporting fuel that no longer behaves like diesel. Pull up wherever you are — the verge on The Broadway, a lay-by, a side street — then leave the car where it is. A car stopped early very seldom has permanent damage, since the fuel drain and the flush, which still come first, sort it out.
Myths Wimbledon drivers hear about petrol in a diesel
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. A fuller tank of the same mixture is all it gives, because topping up takes out nothing. The assumption behind that guidance — that diesel fuel systems accept petrol by percentage — is wrong.
"Modern diesels can handle a little petrol" — a myth, and closer to the opposite. Lubrication matters more on newer diesels, not less, since their fuel runs through finer components at higher pressure.
"It starts, it drives, and so there is no harm" — the myth that trips up more drivers than any other. Diesel in a petrol motor generally means a motor that will not run: the driver stops, and so does the damage. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile your pump grinds. A running engine doesn't mean fine.
An old workaround for a different issue is behind this one. Myth: "Add some two-stroke oil and drive the car home." None of what petrol thinned gets put back by it — and later, that tank still contains the petrol.
Myth: "Drain the tank yourself and you are sorted." After the engine has run, some of the petrol is no longer in that tank: it is in your filter and the lines, and it goes right back through your pump on your next start. Clearing petrol into a can by the kerbside is also truly dangerous.
Why petrol in a diesel takes place at all
On purpose? Never. Through carelessness? Seldom, if ever. The petrol nozzle is the narrower of the two and slips into a diesel filler with almost no resistance; a diesel nozzle mostly won't go into a petrol vehicle at all. The forecourt makes it easy, and the slip runs one way.
It takes place when habit and the vehicle stop matching. Any motor that's new to you — a hire car, on loan as a courtesy car, or just bought. A household with one petrol and one diesel on the drive. A well-known forecourt with the pumps in a different order. Filling up in a rush on the way to the nearest station, with a train to catch. A new-to-you diesel Volkswagen Golf, its first fuelling, and a driver used to petrol: exactly when it happens. With rain, a call coming in, or children to deal with, your hand just does what it always has.
Next time you fill up in Wimbledon: avoiding petrol in a diesel
- The label is what matters, and so check the petrol pump instead of the colour: in the UK unleaded handles are usually green and diesel black, yet not on every forecourt.
- Many motors state the fuel type inside the filler flap or on the cap, so check it on your first fill in any motor you don't know.
- Label your key. In a household with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of intending to remember.
- Before the nozzle comes off the pump the first time you fill a hired or new vehicle, say "diesel" aloud. Daft, perhaps, but it works.
- While you are thinking about something else, this is an easy mistake to make — so tuck the phone away.
- Some diesels have a filler designed to refuse a petrol nozzle, and devices you can add are available for vehicles without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop checking the pump.
- Noticing it halfway? Stop there and then. A weaker blend follows from less petrol in the tank, yet the next step stays the same: do not fire it up.
Already put petrol in a diesel in Wimbledon?
Then the order of things is short. Don't turn your ignition on, and do not fire it up. Yet at the forecourt, at Esso or anywhere else? Ask the attendants to help you push the vehicle away from the petrol pump. What was put in, about how much, and if it has run: tell us that when you phone 0333 366 0103.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost lubrication, make it a different problem — Wimbledon has a page all for it.
Wimbledon petrol in a diesel jobs: why one costs more than another
There's no honest single quote for this, since the four situations above are four different tasks. Chiefly, the cost moves with which one you are in. Next it's the proportion — how much petrol got in against how much the tank takes — and then where the car is and whether a van can get to it safely.
Before any quote, not after, we ask three questions: the fuel that was put in, the amount, and if it's run. That's why. Those answers are what change a range into one firm number.
About Wimbledon
Wimbledon is a locality in south-west London, situated approximately 6.9 miles from central London and 6.5 miles from Westminster. Wimbledon lies near several other local areas, including South Wimbledon, Merton Park, and Wimbledon Common, and is characterised by its predominantly flat-type housing. Wimbledon has a population of around 6463 people and is set in a relatively low-lying area at an elevation of 27 metres. Wimbledon is a distinct and separate area within the larger London urban landscape.
Wimbledon and Greater London: where our fuel drain cover runs
South Wimbledon, Merton Park and Wimbledon Common are among the locations around Wimbledon that the same vans work, answering petrol in diesel call-outs across Wimbledon's SW postcode area. You need not bring the car to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all places where we work.
Wimbledon: still at the petrol pump?
Then you are in the best position there is. Phone, and keep it turned off.