Should You Worry? Petrol in a Diesel Car in Speenhamland
Unstarted? Then less anxious than you probably are. Petrol sitting in a diesel tank does nothing to the engine till something draws it through the fuel system — the ignition priming the pump, the starter, or driving itself. So the fair answer to the first query anyone in Speenhamland asks, "have I wrecked it?", is usually no. Keep it that way: leave your motor off then phone Petrol in Diesel. The remainder of this page sets out what petrol actually does to a diesel, how to judge how far it has got, and how to make sure it doesn't happen to you a second time.
The engine and petrol in a diesel: what goes on
On its way through a motor, diesel has two tasks. Oiling comes before burning; it does both. Extremely fine tolerances go into the injectors and your high-pressure pump, and only the diesel flowing through stops their surfaces grinding together.
Badly at the first, not at all at the second: that's petrol. Being less viscous than diesel, petrol strips away the lubrication a fuel system needs, so a pump on the mixture to wear itself. It is equally made to resist igniting under compression — the reverse of what a diesel needs — which is why you hear the clattering.
Combined, those leave the shape of the trouble plain. The harm is done by circulation, not by contact. Where the petrol is only inside the tank, it is a fault of fuel, nothing more. The beginning of a mechanical problem is a pump that has been working on that petrol — and whatever a worn pump sheds travels on with your fuel to the injectors downstream.
Four scenarios our engineers see around Speenhamland: how serious is petrol in a diesel?
Fuelled but not once started — as good as it gets. At a forecourt, and genuinely only there, the petrol is still confined to that tank — since everywhere else the car was driven to get to it. The task is draining and rinsing on the spot.
A brief spell of running, or just the ignition on. With the fuel system primed, your lines and filter now hold petrol that came from that tank. Drain, flush, deal with your filter: still usually simple.
Those few miles driven meant the pump labouring on fuel diluted by petrol throughout. Distance is only half of it; how hard it was driven matters just as much. Either way this work includes that tank, your lines, the fuel filter and fresh fuel through the entire system. The school run to Speenhamland School is one matter. Driving as far as Winchester, under 25 miles away, makes a very different task — as does any distance on the M4, under 5 miles from Speenhamland, with your engine working hard all the way.
It complained, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone uneven. What you are hearing is the motor reporting fuel that no longer runs like diesel. Stop wherever you are — the verge on Oxford Street, a lay-by, a side street — then leave the car there. Long-term damage is very uncommon if a car is pulled over soon, and the drain and flush that still come first deal with it.
What Speenhamland motorists get told about petrol in a diesel — and the myths in it
Myth: topping up to full with diesel makes it fine. It does not. A bigger tank of the same mixture is all you get, because topping up removes nothing. That guidance supposes a diesel fuel system tolerates petrol by percentage. It doesn't.
"Current diesels can handle a little petrol" — a myth, and nearer the reverse. Protection counts more on current diesels, not less, since their fuel passes through finer parts at higher pressure.
This is the one that fools drivers. Myth: "If it starts and drives, there's no damage done." Diesel in a petrol motor usually leaves a motor that will not run: the motorist stops, and so does the harm. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually does; meanwhile your pump grinds. Being able to run isn't the same as being fine.
Myth: "Add some two-stroke oil and drive the vehicle home." It is an outdated fix for a separate fault. What petrol has thinned remains diluted, and that petrol stays inside that tank anyway.
"Drain it yourself and you are sorted" — a myth, because after it's been running some petrol lies in your filter and lines, waiting to go right back through your pump at your next start. And, a can of petrol drained at the kerbside is genuinely risky.
How petrol ends up: petrol in a diesel
It is seldom carelessness, and nobody does it on purpose. A diesel nozzle generally won't fit a petrol vehicle, but the smaller petrol nozzle goes into the filler of a diesel nearly without resistance — so forecourts make this one error simple, and just in that direction.
Routine and your car falling out of step is when it occurs. Hire cars, courtesy cars, and vehicles that are new to you. Households running one of each, petrol and diesel. The pumps in a different order on a familiar forecourt. Fuelling up in a hurry en route to Newbury, with a train to catch. Years of petrol cars behind you, a diesel Renault Megane in front of you on the forecourt for its first tank — that's when. The hand repeats what it has always done when you add rain, a phone call or a back seat full of children.
Next time you fill up around Speenhamland: preventing petrol in a diesel
- The label is what matters, so read the petrol pump rather than the colour: in the UK unleaded handles are normally green and diesel black, but not on each forecourt.
- Plenty of motors state the fuel type inside your filler flap or on the cap, so check there on your first fill in any car you do not know.
- A coloured fob or a sticker on the diesel's key does more than any amount of intending to remember, for a household with one of each.
- Say it before you lift it. On the first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the pump. It sounds daft and it works.
- Mistakes like this are simple to make while your mind is on something else, and so the phone goes away.
- Some diesels have a filler designed to reject 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 reading the petrol pump.
- Stop the moment you notice. Less petrol inside the tank makes a weaker mixture. It does not change what to do next, which is still not to fire it up.
Speenhamland: already put petrol in a diesel?
Then, there's just a short order of things. Never crank it, and don't switch your ignition on. Still on the forecourt, at Shell or anywhere else? Ask the staff to help you push it clear of the petrol pump. Then phone 0333 366 0103 and tell us what went in, roughly how much, and whether it's run.
If it was AdBlue and not petrol, say so. That is a separate problem — corrosion and deposits and not lost lubrication — and it has its own page for Speenhamland.
Why one petrol in a diesel task in Speenhamland costs more than another
The four situations above are four different tasks, so no single quote for this would be fair. The situation itself does most of the work of moving your cost. Beyond that it's the ratio — how much petrol got in against how much the tank takes — and after that where your car is and whether our van can get to it safely.
What got in, how much, and if it has run — three queries we ask before quoting, not after, for precisely that reason. A range turns into a straight figure once the replies are in.
About Speenhamland, for a moment
Speenhamland is a suburban area in Berkshire, situated on the banks of the River Kennet at an elevation of around 85 metres. Speenhamland lies near the town of Newbury and is close to other nearby places such as Shaw and West Fields. Speenhamland is characterized by its predominantly flat housing stock and its proximity to the countryside, while also being within commuting distance of major cities like London and Winchester.
Across Berkshire and around Speenhamland: fuel drain cover
Newbury, Shaw and West Fields are among the spots around Speenhamland that the same vans work, answering petrol in diesel calls across Speenhamland's RG postcode area. You need not bring the vehicle to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all locations where we work.
Speenhamland: still at the pump?
Nothing beats it: that is where you now are. Leave it turned off, and ring.