Robinsons End: Petrol in a Diesel Car? How Worried to Be
Probably less than you are now — as long as nobody has started the car. Petrol sitting in a diesel tank does nothing to the engine till something draws it through your fuel system — your ignition priming your pump, the starter, or driving on its own. So the honest answer to the first question everyone in Robinsons End asks, "have I wrecked it?", is generally no. Keep it that way: leave your motor off then ring Petrol in Diesel. Further down, you will find what petrol actually does inside a diesel, how far it may have got, and how to stop it happening to you again.
Inside your engine: what petrol in a diesel does
Passing through an engine, diesel is doing two things at once. It protects first, and only then does it burn. What stops the surfaces inside the high-pressure fuel pump and the fuel injectors from wearing down against each other is your diesel passing through them — they are designed to very fine gaps.
Petrol handles the first task badly and the second not at all. Being less viscous than diesel, petrol strips out the protection a fuel system needs, leaving a pump on the blend to wear itself. It's also made to resist igniting under compression — the reverse of what a diesel needs — which is where you hear the rattling.
Seen together, they show the shape the issue takes. Contact doesn't do the damage — movement does. Where that petrol is only inside the tank, it is a problem of fuel, nothing more. Once the pump has been running on that petrol, a mechanical issue has begun: anything shed by a pump that is wearing down is carried onward to the fuel injectors with your fuel.
Four situations our engineers see around Robinsons End: how serious is petrol in a diesel?
Filled but never started — the best it gets. That petrol is inside your tank and only the tank, and the task is a drain and a flush where your car sits. This is the one scenario that can only really occur on a forecourt, because anywhere else the car has been driven to get there.
The ignition switched on, or a brief start. Once primed, the fuel system has pulled petrol out of the tank as far as the fuel filter and the fuel lines. Still usually easy: drain, flush, and the fuel filter dealt with.
Driven a couple of miles. Now the pump has spent these miles labouring on thinned fuel. How hard the car was driven counts as much as how far, and the work covers your tank, the lines, the fuel filter and clean fuel through the whole circuit. Driving the kids to Park Lane Primary School is one kind of trip. Very different a second time: a run to Coventry, under 10 miles away, or some distance on the M6, under 5 miles from Robinsons End, where the motor never stopped working hard.
Clattering, a lumpy idle, smoke, a throttle gone soft: driven till it complained. That is your motor telling you its fuel has stopped behaving like diesel. Whether it is the verge on Thorntons Way, a lay-by or a side road, stop there and leave it. What goes first is still the drain and flush-through, and that takes care of it, with permanent damage very unusual if a vehicle is pulled over quickly.
Myths Robinsons End people 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 by topping up — you're left with a bigger tank, still the same mix. A diesel fuel system doesn't accept petrol by percentage in the way that advice assumes.
Myth: "A current diesel can cope with a bit of petrol." If anything, the opposite. A current diesel runs its fuel through finer parts at higher pressure, which makes the lubrication count more, not less.
This is the one that catches drivers. Myth: "If it starts and drives, there's no damage done." A petrol engine fed diesel usually won't run, so the motorist stops and the harm 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. Fine and running aren't the same thing.
An old fix for a distinct issue is behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." What petrol has diluted stays weakened, and the petrol stays in that tank anyway.
"Drain it yourself and you're sorted" — a myth, since after it has been running some petrol sits in the fuel filter and lines, waiting to go straight back through your pump at your next start. It is also genuinely risky to drain petrol into a can at the roadside.
How does petrol in a diesel take place?
It is rarely carelessness, and no one does it on purpose. The petrol nozzle is the slimmer of the two and slips into a diesel filler with almost no resistance; a diesel nozzle mostly won't go into a petrol car at all. The forecourt makes it simple, and the mistake runs one way.
When routine and your car stop matching, it occurs. 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 driveway. A forecourt you know, but with its pumps arranged differently. Fuelling up in a rush en route to Bermuda Park, with a train to catch. The first fill-up in a diesel Volkswagen Passat after years of driving petrol is precisely the moment it happens. The hand repeats what it has always done when you add rain, a phone call or a back seat full of children.
How to avoid petrol in a diesel on your next fill-up in Robinsons End
- A green handle for unleaded and black for diesel is normal in the UK — but not on each forecourt. Go by the label on the pump, not the colour.
- In a vehicle you do not know, look inside the flap over the filler or at the cap before the first fill: plenty of motors state the fuel type there.
- Good intentions count for less than a sticker or a fob in a vivid colour on your diesel's key when a house has one of each. So label it.
- Say it before you lift it. On the first fill in a new or hired car, say "diesel" aloud before you take the nozzle off the pump. It sounds daft and it works.
- Put the phone away. This is an easy mistake to make while you're thinking about something else.
- Add-on devices exist for motors without one, and some diesels come with a filler that won't take a petrol nozzle. Helpful — but a safety net at best, never a reason to stop checking the label.
- Spotting it halfway? Stop at once. A thinner mixture follows from less petrol in that tank, but the next step stays the same: do not fire it up.
Put petrol in a diesel around Robinsons End already?
Then the order of things is short. Do not start the car, and do not switch the ignition on. The attendants on the forecourt — whether at the nearest petrol station itself or wherever you filled up — will normally help roll it clear of the pump if you ask. Then call 0333 366 0103 and tell us what was put in, about how much, and if it has run.
Corrosion and deposits form the problem with AdBlue, where petrol brings lost lubrication. So if it was AdBlue, say so — and read its own Robinsons End page.
What makes one Robinsons End petrol in a diesel job cost more than the next
The four situations above are four separate tasks, so no single quote for this would be honest. Which of them you are in is chiefly what shifts the cost. Where the car is matters too, and whether a van can safely get to it, after the ratio of petrol to what your tank holds.
What got in, how much, and whether it has run — three questions our engineers ask before quoting, not after, for exactly that reason. Their replies are what turn a range into one firm number.
About Robinsons End, for a moment
Robinsons End is a suburban area situated lakeside in Warwickshire, with a mix of terraced housing and local amenities. Robinsons End sits at an elevation of 139 metres, approximately 7.6 miles from Coventry and 91.6 miles from London. Robinsons End is surrounded by nearby places such as Galley Common, Stockingford, and Whittleford, and has a population of around 3246 residents.
Robinsons End and Warwickshire: where our fuel drain cover reaches
Galley Common, Stockingford and Whittleford are among the locations near Robinsons End that the same vans work, answering petrol in diesel call-outs across Robinsons End's CV postcode area. The car does not need to come to us: our technicians drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
Still at the petrol pump in Robinsons End?
Then you are in the best position there can be. Keep the car turned off, and ring.