How Worried Should You Be? Petrol in a Diesel Car in Lent
Far less than you likely are, provided it hasn't been started. Petrol sitting in a diesel tank does nothing to the engine until something draws it through your fuel system — your ignition priming your pump, the starter, or driving on its own. So the truthful answer to the first question everyone around Lent asks, "have I wrecked it?", is generally no. To leave it like that, call Petrol in Diesel and leave the engine switched off. Read on for three things: the effect petrol has inside a diesel motor, the signs of how far it has got, and ways to make sure you don't repeat it.
Inside the motor: what petrol in a diesel does
On its way through a motor, diesel has two tasks. It ignites, and before it combusts it protects. Extremely fine clearances go into your injectors and the high-pressure pump, and only your diesel running through stops their surfaces grinding together.
Petrol handles the first task badly and the second not at all. A pump running on a petrol mix is wearing itself out, since petrol is runnier than diesel and strips out the protection your fuel system depends on. Petrol is also made to resist igniting under compression — the opposite of what a diesel needs from its fuel — and that is where the clattering starts.
The shape of the problem is plain when you put those together. It is movement that causes the damage, not contact. All a tank with petrol in it amounts to is a fuel fault. The beginning of a mechanical problem is a pump that has been labouring on that petrol — and whatever a worn pump sheds travels on with your fuel to the fuel injectors beyond it.
Lent, petrol in a diesel: four situations, from mild to serious
Filled up, never started. The best case there can be. On a forecourt, and truly only there, the petrol is still limited to that tank — since anywhere else the car was driven to reach it. The job is draining and flushing on the spot.
Ignition on, or started for a second. With the system primed, the fuel lines and filter now hold petrol that came from that tank. Still normally simple: drain, flush, and the filter sorted.
The pump now spent a couple of miles on weakened fuel — that's what driving the car does. The work is the tank, the fuel lines, the fuel filter and clean fuel through the whole circuit, and how hard your car was driven counts as much as how far. On the school run to St Peter's Church of England Primary School, the distance is short. Driving as far as St Albans, under 25 miles away, makes a very different task — as does any miles on the Huntercombe Spur, under 3 miles from Lent, with your engine labouring hard the whole time.
Driven on until it protested — knocking, smoke, a ragged idle, a dead throttle. The fuel is not behaving like diesel any more, and the engine is saying so. Stop wherever you are — the verge on Lent Rise Road, a lay-by, a side street — then leave it where it is. Permanent damage is very rare when a vehicle is pulled over soon, and the drain and flush-through that still go first sort it out.
Lent drivers and the petrol in a diesel myths they hear
Myth: topping up to full with diesel makes it fine. It doesn't. Nothing is removed by topping up — you're left with a bigger tank, still the same mixture. The idea behind that guidance — that diesel fuel systems accept petrol by percentage — is wrong.
Not so: a newer diesel copes with a bit of petrol. Rather, the reverse. At higher pressure, through smaller parts: that's how a modern diesel handles its fuel, so the lubrication matters more, not less.
This is the one that fools drivers. Myth: "If it starts and drives, there's no damage done." Diesel in a petrol motor usually means a motor that won't run: the driver stops, and so does the damage. Feed petrol to a diesel and it generally starts, ticks over and drives away as if nothing has happened — all while its pump wears. Fine and running are not the same thing.
Myth: a two-stroke additive makes it safe to drive home. It is an old workaround, meant for another fault. None of what petrol thinned gets put back by it — and afterwards, that tank still contains the petrol.
The next start draws petrol back round your pump from the fuel lines and the filter, where some of that ends up after the engine has been run. That is why draining your tank yourself doesn't sort it — a myth. Besides, petrol emptied into a can by the road is genuinely risky.
How does petrol in a diesel happen?
It's rarely carelessness, and no one does it on purpose. The forecourt makes it easy: the petrol nozzle is the smaller of the two, and it slips into a diesel filler with almost no resistance, whilst a diesel nozzle generally will not go into a petrol car at all. So the mistake runs one way.
The moment routine stops matching your car is the moment it takes place. Courtesy car, hire car, or a motor that is brand new. Two vehicles on one driveway, one petrol, one diesel. A familiar forecourt with the pumps in a different order. Fuelling up in a hurry on the way to Taplow, with a train to catch. The first fill-up in a diesel Renault Megane after years of driving petrol is exactly the moment it takes place. With rain, a call arriving, or a car full of children to deal with, the hand just does what it has always done.
How to avoid petrol in a diesel at your next fill-up in Lent
- The label is what counts, so check the pump instead of the colour: in the UK unleaded handles are usually green and diesel black, yet not on each forecourt.
- Check the filler flap. Plenty of vehicles state the fuel inside the flap or on the cap. Look at it on your first fill in a motor you don't know.
- A coloured fob or a sticker on your diesel's key does more than any amount of intending to remember, in a home 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 lift the nozzle off the pump. It seems daft and it does the trick.
- Whilst you're thinking about something else, this is an easy mistake to make — so tuck the phone away.
- Add-on devices are available for vehicles without one, and some diesels come with a filler that won't take a petrol nozzle. Helpful — but a backstop only, never a reason to stop checking the label.
- Less petrol makes a thinner mixture, and so stop as soon as you realise — though remembering that your next step is unchanged. It is still not to start the vehicle.
Petrol already in a diesel around Lent? Start here
The order of things is brief, then. Do not fire it up, and don't turn your ignition on. Yet at the forecourt, at Esso or anywhere else? Ask the staff to help you roll it clear of the petrol pump. Then phone 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 problem, with its own page for Lent, since AdBlue brings corrosion and deposits instead of lost lubrication.
Why one petrol in a diesel job around Lent costs more than another
Four separate tasks lie behind the four scenarios above — which is why there's no honest single quote. Mostly, the cost moves with which situation you're in. Two things follow that: the petrol that went in as a proportion of what your tank takes, then the place the vehicle is in and whether our van can reach it safely.
Ahead of any quote, not after, come three queries: your fuel that got in, the volume, and if it has run. That's why. With the replies, there is a straight figure instead of a range.
About Lent, briefly
Lent is a locality in Buckinghamshire, situated inland at an elevation of 55 metres, approximately 23 miles west of London. Lent lies near several other small settlements, including Lent Rise, Hitchambury, and Burnham, and is close to the city of St Albans. Lent has a population of around 1617 people, predominantly living in semi-detached housing.
Fuel drain cover in Lent and across Buckinghamshire
Lent rests in the SL postcode area, and our vans that answer petrol in diesel jobs there work the spots near it as well — Lent Rise, Hitchambury and Burnham among them. You need not move the car to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all places where we work.
Still at the pump in Lent?
The best spot there is, then — that is where you are. Switched off it stays; then phone.