How Worried Should You Be? Petrol in a Diesel Car in Fiddlers Hill
Provided it has not been started, you can worry less than you probably are. 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 itself. So the fair answer to the first question everyone around Fiddlers Hill asks, "have I wrecked it?", is usually no. Petrol in Diesel is who to ring, with your engine kept off, so it stays that way. Further down, this page sets out what petrol actually does inside a diesel, how far it might have got, and how to stop it happening to you again.
What petrol in a diesel does to the motor
Passing through an engine, diesel does two jobs at the same time. It combusts, and before it combusts it protects. Extremely fine clearances are built into your injectors and the high-pressure fuel pump, and just the diesel flowing through stops their surfaces grinding together.
Petrol does the first task badly and the second not at all. Being less viscous than diesel, petrol strips away the lubrication a fuel system needs, so a pump on that mixture to wear itself. It is also made to resist igniting under compression — the opposite of what a diesel needs — which is why you get the knocking.
Together, those leave the shape of the trouble plain. The damage is done by circulation, not by contact. Where that petrol is only inside that tank, it's a problem of fuel, nothing more. After your pump has been running on that petrol, a mechanical fault has started: anything shed by a pump that is wearing down travels downstream to your injectors with your fuel.
Fiddlers Hill, petrol in a diesel: four situations, from mild to major
Filled up, and not started: nothing beats it. Being on a forecourt is what makes this the case: elsewhere, your car has been driven there to begin with. With the petrol kept in the tank alone, it's cleared and flushed right where it stands, and nothing more is needed.
Ignition on, or started for a second. Once primed, your system has pulled petrol out of the tank as far as the fuel filter and your lines. Normally little more than clearing, rinsing and seeing to your filter, so still straightforward.
A few miles driven, and the pump has spent each of them labouring on thinned fuel. The work is the tank, your lines, the fuel filter and clean fuel through the entire circuit, and how hard the vehicle was driven counts as much as how far. Driving the kids to Wood End School is one sort of trip. Very different again: a trip to St Albans, under 10 miles away, or some mileage on the M1, under 3 miles from Fiddlers Hill, where the engine never stopped labouring hard.
Rattling, a lumpy idle, smoke, a throttle gone soft: driven till it complained. That's the motor telling you its fuel has stopped behaving like diesel. Pull up wherever you are — the verge on The Common, a lay-by, a side street — and leave the vehicle there. A car stopped soon very seldom has lasting damage, since the drain and the flush-through, which still come first, sort it out.
Myths Fiddlers Hill motorists hear about petrol in a diesel
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Nothing is removed by topping up — you're left with a bigger tank, still the same mix. The assumption behind the advice — that diesel fuel systems tolerate petrol by percentage — is wrong.
"Modern diesels can handle a little petrol" — a myth, and closer to the opposite. A newer diesel sends its fuel through smaller components at higher pressure, which makes the protection matter more, not less.
One myth that catches drivers off guard: if it starts and drives, it must be unharmed. Any petrol motor fed diesel generally will not run, so the motorist stops and the harm stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, which it usually will; meanwhile the pump grinds. Fine and running aren't the same thing.
An old fix for a distinct fault is behind this one. Myth: "Add some two-stroke oil and drive it home." It doesn't put back what petrol has weakened, and the petrol is still inside your tank later on.
Myth: "Drain your tank yourself and you are sorted." Once the engine has run, some of the petrol is no longer in the tank: it is in the fuel filter and the fuel lines, and it goes straight back through the pump at your next start. Besides, petrol cleared into a can by the road is genuinely hazardous.
How petrol ends up: petrol in a diesel
On purpose? Never. Through carelessness? Seldom, if ever. A diesel nozzle generally will not fit a petrol vehicle, but the slimmer petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake straightforward, and just in one direction.
It occurs when routine and your car stop matching. Courtesy car, hire car, or a motor that's brand new. Two vehicles on one drive, one petrol, one diesel. A well-known forecourt with the pumps in a different order. A train to catch, and a rushed fill en route to Harpenden. Exactly the moment it takes place: after years of driving petrol, someone fills a diesel Volkswagen Golf for the first time. The hand does what it has always done once you add rain, a phone call or a back seat full of kids.
Fiddlers Hill motorists: how to prevent petrol in a diesel next time
- Check the pump, not the colour. In the UK unleaded handles are usually green and diesel black, but not on each forecourt. The label is what matters.
- Check your filler flap. Many cars state the fuel inside the flap or on the cap. Look at it on your first fill in any car you do not know.
- Mark your key. In a home with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of intending to remember.
- 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 petrol pump. It sounds silly and it does the trick.
- Thinking about something else is when this becomes an easy mistake to make, so put your phone away and keep your mind on the pump.
- Add-on devices exist for cars without one, and some diesels are built with a filler that will not accept a petrol nozzle. Helpful — but a backstop at best, never a reason to stop checking the label.
- The moment you notice, stop: less petrol in that tank makes a thinner mix. What to do next doesn't change, though — still don't start the vehicle.
Petrol already in a diesel in Fiddlers Hill? Start here
Then the order of things is brief. Starting it is out, and so is turning on your ignition. Ask the staff to help you push it clear of the pump if you're still at the forecourt, whether that's BP or anywhere else. Then ring 0333 366 0103 and tell us what went in, about how much, and whether it has run.
Say so if it was AdBlue instead of petrol: it is a different issue, with its own page for Fiddlers Hill, because AdBlue brings corrosion and deposits instead of lost lubrication.
Why one petrol in a diesel job around Fiddlers Hill costs more than another
A fair single price does not exist here: four situations, four separate tasks. The scenario itself does most of the work of moving your cost. The proportion counts next, meaning how much of that tank is petrol, and then the position of the vehicle and whether reaching it is safe for a van.
That's why our engineers ask three questions before costing rather than after: what got in, how much, and if it has run. A range turns into a straight figure when those answers are in.
About Fiddlers Hill itself
Fiddlers Hill is a suburban area in Hertfordshire, situated approximately 25 miles northwest of London and 5.8 miles southeast of St Albans. Fiddlers Hill sits at an elevation of around 121 metres, amidst the rolling countryside of the Eastern region. Fiddlers Hill is characterised by its predominantly detached housing stock, with nearby places including Thrales End, West Hyde, and Kinsbourne Green.
Fiddlers Hill and Hertfordshire: where our fuel drain cover runs
Thrales End, West Hyde and Kinsbourne Green are among the locations near Fiddlers Hill that the same vans work, answering petrol in diesel jobs across Fiddlers Hill's AL postcode area. You need not move your car to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all places we drain.
Fiddlers Hill: still at the petrol pump?
Then, you couldn't be in a better place. Phone, and keep it switched off.