Sandhurst: Petrol in a Diesel Car? How Worried to Be
Likely less than you are now — provided no one has started it. Till the ignition primes your pump, your starter turns, or the vehicle is driven, petrol in a diesel tank simply waits there and does nothing. Which makes the truthful reply to that first Sandhurst query — "have I ruined it?" — normally no. Keep it like that: leave your engine off and phone Petrol in Diesel. 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 don't do it again.
Inside the motor: what petrol in a diesel really does
Diesel does two tasks on its way through a motor. Lubricating comes before burning; it does both. What stops the surfaces inside the high-pressure fuel pump and the fuel injectors from grinding against each other is your diesel passing through them — they're designed to very fine tolerances.
Badly at the first, not at all at the second: that's petrol. Being less viscous than diesel, petrol strips out the protection a fuel system needs, leaving a pump on the blend wearing itself. It's also made to resist igniting under compression — the opposite of what a diesel needs — which is where you hear the knocking.
Seen together, they show the shape the problem has. It is circulation that does the damage, not contact. Petrol in the tank is a fuel issue. Whatever a worn pump sheds goes on, carried by the fuel, into your injectors further along, which is why a pump that has worked on the petrol is where a mechanical issue starts.
Four scenarios our technicians see around Sandhurst: how serious is petrol in a diesel?
Filled but not once started — the best it gets. At a forecourt, and genuinely only there, that petrol is still confined to your tank — because anywhere else the car was driven to get to it. The task is draining and purging on the spot.
Ignition on, or started for a second. Once primed, the fuel system has pulled petrol out of the tank as far as the fuel filter and the lines. Usually little more than clearing, purging and sorting the fuel filter, and so still straightforward.
Your pump has spent a couple of miles on diluted fuel — that's what driving the car meant. The work is the tank, your lines, the fuel filter and clean fuel through the entire circuit, and how hard your car was driven matters as much as how far. On the school run to Uplands Primary School and Nursery, the mileage is small. A run as far as Winchester, under 50 miles away, is a very different task. So is any mileage on the M3, under 3 miles from Sandhurst, where the engine has been labouring hard throughout.
It complained, and only then stopped: smoke, knocking, a throttle gone soft, an idle gone uneven. The fuel is not behaving like diesel any more, and your motor is saying so. Pull up where you are — on the verge on Yorktown Road, at the kerb, down a side road — and don't move it again. Permanent damage is very unusual when a car is stopped quickly, and the fuel drain and flush that still go first take care of it.
What Sandhurst people get told about petrol in a diesel — and the stories in it
Myth: topping up to full with diesel makes it fine. It does not. Topping up takes out nothing; it gives you a bigger tank of the same mixture. That advice assumes a diesel fuel system tolerates petrol by percentage. It doesn't.
If anything, the opposite is true. Myth: "A current diesel can cope with a bit of petrol." Smaller parts and higher pressure are the way a newer diesel runs its fuel, and that makes the lubrication matter more, not less.
This is the one that catches people. Myth: "If it starts and drives, there's no harm done." The driver of a petrol motor fed diesel normally has no choice but to stop, because it will not run, and the damage stops with them. Whilst the pump wears, a diesel fed petrol usually starts, idles and drives away as if nothing has happened. Fine and running are not the same thing.
Not so: a two-stroke additive lets you to drive home. It is an old fix, meant for another problem. It does not put back what petrol has weakened, and the petrol is still in the tank after that.
"Drain it yourself and you're sorted" — a myth, since after it has been running some petrol lies in the filter and lines, ready to go straight back through the pump at your next start. And, a can of petrol filled by the roadside is truly risky.
Why petrol in a diesel takes place so easily
No one does it on purpose, and it's seldom carelessness. The forecourt makes it easy: the petrol nozzle is the smaller of the two, and it slides into a diesel filler with almost no resistance, whilst a diesel nozzle mostly will not go into a petrol vehicle at all. So the mistake runs one way.
The moment habit stops matching the vehicle is the moment it takes place. Courtesy car, hire car, or a motor that is brand new. A household with one petrol and one diesel on the drive. Your usual forecourt, its pumps suddenly in a different order. Fuelling up in a hurry on the way to the nearest station, with a train to catch. A new-to-you diesel Renault Megane, its first fuelling, and a driver used to petrol: precisely when it occurs. With rain, a call coming in, or a car full of children to deal with, your hand just does what it always has.
Sandhurst people: how to prevent petrol in a diesel next time
- Read the pump, not the colour. In the UK unleaded handles are normally green and diesel black, yet not on each forecourt. The label is what counts.
- In a car you do not know, look inside the flap over your filler or at the cap before your first fill: many motors state the fuel there.
- A coloured fob or a sticker on the diesel's key achieves more than any amount of meaning to remember, for a household with one of each.
- It seems daft and it works: on the first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the petrol pump.
- Whilst you are thinking about something else, this is an easy mistake to make — so put your phone away.
- Add-on devices exist for cars without one, and some diesels are built with a filler that will not accept a petrol nozzle. Useful — but a safety net only, never a reason to stop checking the label.
- As soon as you realise, stop: less petrol in that tank means a weaker blend. What to do next does not change, though — still don't fire it up.
Put petrol in a diesel around Sandhurst already?
Then, there is only a short order of things. Do not switch the ignition on, and don't crank it. The attendants on the forecourt — whether at Esso itself or wherever you filled up — will normally help push it clear of the petrol pump if you ask. Next, 0333 366 0103. We will ask what got in, about how much, and if it has been run.
If it was AdBlue and not petrol, say so. That is a separate issue — corrosion and deposits instead of lost lubrication — and it has its own page for Sandhurst.
Sandhurst petrol in a diesel tasks: why one costs more than another
The four scenarios above are four separate tasks, so no single quote for this would be honest. The situation itself does most of the work of moving your cost. The proportion counts next, meaning how much of that tank is petrol, followed by the position of the car and whether getting to it is safe for our van.
That's why we ask three questions before costing instead of after: what was put in, how much, and if it's run. A range becomes a straight figure once those answers are in.
About Sandhurst, briefly
Sandhurst is a town in Berkshire, situated on the banks of the Blackwater River at an elevation of around 63 metres. Sandhurst lies approximately 31 miles west of London and is close to the nearby towns of Yateley and Winchester. Sandhurst has a population of around 16732 people and is characterised by predominantly detached housing. Sandhurst is also near smaller settlements such as Little Sandhurst and Darby Green.
Fuel drain cover across Berkshire, Sandhurst included
Sandhurst waits in the GU postcode area, and our vans that answer petrol in diesel jobs there work the places around it as well — Little Sandhurst, Darby Green and Yateley among them. The vehicle does not need to come to us: we drain at a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
Sandhurst: still at the pump?
Then you are in the best spot there is. Turned off it stays; then phone.