Mayford: Petrol in a Diesel Car? How Worried to Be
Far less than you probably are, if it has not been started. "Have I wrecked it?" is the first thing everyone in Mayford asks, and the truthful answer is generally no, since petrol resting in a diesel tank harms nothing until it is drawn through the fuel system — by ignition priming, by the starter, or by driving. Leave your engine off then phone Petrol in Diesel — that is how you keep it that way. Keep reading for three things: the effect petrol has inside a diesel engine, the signs of how far it has got, and ways to make sure you don't repeat it.
What petrol in a diesel does to your engine
Passing through a motor, diesel does two jobs at the same time. It lubricates first, and only then does it burn. Very fine gaps are built into the fuel injectors and the high-pressure pump, and only the diesel running through keeps their surfaces from grinding together.
Poorly at the first, not at all at the second: that is petrol. Being less viscous than diesel, petrol strips out the lubrication a fuel system needs, leaving a pump on that mixture wearing itself. It is equally made to resist igniting under compression — the reverse of what a diesel needs — which is where you hear the clattering.
The shape of the problem is plain once you put those together. It's movement that causes the harm, not contact. Where that petrol is only inside the tank, it is a problem of fuel, nothing more. Whatever a worn pump sheds travels on, borne by your fuel, into the injectors further along, which is why a pump that has been working on the petrol is where a mechanical problem begins.
How bad is petrol in a diesel? Four scenarios our technicians see around Mayford
Filled up, never started. The best case there can be. That petrol is in that tank and only your tank, and the task is a drain and a flush where the car stands. This is the one situation that can only truly happen at a forecourt, because anywhere else the vehicle has been driven to get there.
A brief spell of running, or just your ignition on. Your system has been primed, and so petrol has left your tank and reached the filter and your lines. Drain, flush, deal with the fuel filter: still usually straightforward.
Driven a few miles. Now your pump has spent those miles running on diluted fuel. Tank, lines, filter, then clean fuel run through the whole circuit: that's the work, and the way the car was driven matters as much as the distance. Short trips, like the school run to Westfield Primary School, are one thing. Any distance on the M25, under 5 miles from Mayford, means the engine has worked hard throughout, and a run to Westminster, under 25 miles away, makes a very different job too.
It complained, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone uneven. What you are hearing is the engine reporting fuel that no longer acts like diesel. Whether it's the verge on Mayford Roundabout, a lay-by or a side road, stop there and leave it. The drain and flush still go first, and they sort it out: when a car is stopped quickly, long-term damage is very rare.
Myths Mayford drivers hear about petrol in a diesel
"Top it up the rest of the way with diesel and it will be fine" — a myth. It won't. Topping up takes out nothing; it gives you a bigger tank of the same mix. That guidance supposes a diesel fuel system tolerates petrol by percentage. It does not.
Not so: a newer diesel copes with a bit of petrol. Rather, the opposite. Lubrication matters more on newer diesels, not less, since their fuel passes through smaller components at higher pressure.
This is the one that catches people. Myth: "If it starts and drives, there is no damage done." Feed diesel to a petrol motor and it normally won't run, and 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 does; meanwhile the pump grinds. Fine and running are not the same at all.
Not so: a two-stroke additive lets you to drive home. It is an old fix, meant for another problem. It doesn't put back what petrol has thinned, and the petrol is still inside that tank afterwards.
Myth: "Drain the tank yourself and you are sorted." After your engine has run, some of that petrol is no longer inside your tank: it's in your filter and your lines, and it goes straight back through your pump at your next start. It is also genuinely risky to drain petrol into a can by the kerbside.
How petrol ends up: petrol in a diesel
It's seldom carelessness, and no one does it on purpose. One way only, because of the nozzles: the slimmer petrol one slips inside a diesel filler with almost no resistance, while the diesel one mostly won't fit a petrol vehicle. That's how the forecourt makes it straightforward.
It happens when habit and the vehicle stop matching. A motor that is new to you — a hire car, on loan as a courtesy car, or brand new. Two motors on one driveway, one petrol, one diesel. The pumps in a different order on a well-known forecourt. Filling up in a rush on the way to Worplesdon, with a train to catch. Precisely the moment it takes place: after years of driving petrol, someone fills a diesel Volkswagen Golf for the first time. With rain, a call arriving, or children to deal with, the hand just does what it always has.
How to prevent petrol in a diesel at your next fill-up around Mayford
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most generally do. Check the pump's label; the colour is only a hint.
- In a car you don't know, look inside the flap over your filler or at the cap before your first fill: plenty of vehicles print the fuel there.
- A coloured fob or a sticker on the diesel's key achieves more than any amount of intending to remember, in a home with one of each.
- Before the nozzle leaves the petrol pump the first time you fuel a hired or new motor, say "diesel" aloud. Daft, perhaps, yet it works.
- While you're thinking about something else, this is an easy mistake to make — so put the phone away.
- Some diesels have a filler designed to refuse a petrol nozzle, and devices you can add exist for motors without one. Such an inhibitor helps up to a point — as a backstop, not a reason to stop reading the petrol pump.
- Spotting it halfway? Stop there and then. A thinner mixture follows from less petrol inside the tank, yet your next step stays the same: do not crank it.
Already put petrol in a diesel around Mayford?
Then, there's just a short order of things. Do not turn the ignition on, and don't start it. If you are still at the forecourt — Shell or anywhere else — ask the attendants to help you push it clear of the pump. Ring 0333 366 0103 next, with three facts — your fuel, the rough amount, and if it's run.
If it was AdBlue and not petrol, say so. That's a different issue — corrosion and deposits rather than lost protection — and it has its own page for Mayford.
Why one petrol in a diesel task around Mayford costs more than another
There's no honest single quote for this, because the four situations above are four separate tasks. Chiefly, the cost moves with which situation you're in. Two things follow that: the petrol that was put in as a share of what the tank holds, then the spot the vehicle is in and whether a technician can reach it safely.
That's why we ask three queries before costing rather than after: what went in, how much, and whether it has run. The replies change a range into a straight figure.
About Mayford and its setting
Mayford is a suburban area in Surrey, situated near the River Wey and characterised by its detached housing stock. Mayford sits at an elevation of 27 metres, close to the nearby settlements of Pyle Hill and Pray Heath. Mayford is located approximately 24 miles from London, making it a commuter-friendly location. Mayford has a population of around 1435 residents, who enjoy its riverside setting and proximity to Westfield.
Mayford and Surrey: where our fuel drain cover runs
Pyle Hill, Pray Heath and Westfield are among the locations near Mayford that the same vans work, answering petrol in diesel calls across Mayford's GU postcode area. The car doesn't need to move to us: our engineers drain on a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
In Mayford and still at the pump?
Nothing beats it: that's where you are. Turned off it stays; then phone.