Horsham: Petrol in a Diesel Car? How Worried to Be
Probably less than you are now — provided no one has started the vehicle. "Have I ruined it?" is the first thing everyone in Horsham asks, and the truthful answer is normally no, because petrol left in a diesel tank harms nothing until it's dragged through the system — by ignition priming, by your starter, or by being driven. Leave the engine off then call Petrol in Diesel — that is how you keep it that way. The remainder of this page explains what petrol actually does to a diesel, how to tell how far it has got, and how to make sure it does not happen to you a second time.
What petrol in a diesel does to the motor
On its way through a motor, diesel has two jobs. It lubricates to begin with, and only then does it burn. The high-pressure fuel pump and your injectors are built to very fine gaps, and the diesel passing through them is what keeps those surfaces from wearing against each other.
Of those two jobs, petrol manages the first badly and the second not at all. A pump working on a petrol blend is wearing itself out, since petrol is thinner than diesel and strips out the lubrication the fuel system relies on. Petrol is also made to resist igniting under compression — the opposite of what a diesel wants from its fuel — and that is where the knocking starts.
Put those together and the shape of the trouble is clear. Not contact but movement is what causes the harm. Any tank with petrol in it is a fuel fault. The start of a mechanical one is a pump that has been working on that petrol — and whatever a worn pump sheds travels on with the fuel to your injectors downstream.
Horsham, petrol in a diesel: four cases, from mild to major
The best case there is: filled up, not once started. That petrol is inside your tank and just that tank, and the job is a drain and a flush where the vehicle sits. This is the one situation that can only really take place on a forecourt, as anywhere else the vehicle has been driven to get there.
Ignition on, or started for a second. Petrol has left your tank and got to the fuel filter and the lines, because the fuel system has been bled. Drain, flush, deal with the fuel filter: still usually easy.
Some miles driven, and your pump has spent every one of them working on weakened fuel. How hard the car was driven counts as much as how far, and the work takes in that tank, your lines, your filter and clean fuel through the entire system. On the school run to St Mary's CofE (Aided) Primary School, the mileage is small. A run as far as Brighton and Hove, under 25 miles away, is a very different task. So is any miles on the M23, under 10 miles from Horsham, where your engine has been labouring hard the whole time.
Knocking, an uneven idle, smoke, a throttle gone soft: driven until it complained. The engine is telling you the fuel is no longer acting like diesel. Leave it where it has stopped: a lay-by, a quiet street, the verge on Carfax. A car stopped quickly very rarely has lasting damage, as the drain and the flush, which still go first, take care of it.
Petrol in a diesel myths Horsham motorists hear
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. A bigger tank of the same mix is all you get, since topping up takes out nothing. Percentage is not how a diesel fuel system tolerates petrol, however much that advice presumes.
If anything, the opposite holds. Myth: "A newer diesel can cope with a bit of petrol." Lubrication matters more on current diesels, not less, since their fuel runs through smaller parts at higher pressure.
"It starts, it drives, so no harm done" — the myth that trips up most drivers than any other. Diesel in a petrol motor generally leaves a motor that will not run: the motorist stops, and so does the harm. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually does; meanwhile the pump grinds. A running engine does not mean fine.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a separate fault. None of what petrol diluted is put back by it — and later, your tank still holds that petrol.
Myth: "Drain the tank yourself and you are sorted." After the engine has been run, some of that petrol is no longer in the tank: it's in the fuel filter and the fuel lines, and it goes straight back through the pump on your next start. Draining petrol into a can by the kerbside is also genuinely risky.
Why petrol in a diesel occurs so easily
Nobody does it on purpose, and it is rarely carelessness. 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 won't go into a petrol motor at all. So the slip runs one way.
The moment routine stops matching your car is the moment it occurs. Hire cars, courtesy cars, and cars that are new to you. Households running one of each, petrol and diesel. Your normal forecourt, its pumps suddenly in a different order. A train to catch, and a hurried fill en route to the nearest station. The first fill-up in a diesel Renault Megane after years of driving petrol is precisely the moment it takes place. Add a back seat full of children, a phone call or rain, and the hand wins.
Horsham people: how to avoid petrol in a diesel next time
- The label is what matters, and so read the petrol pump instead of the colour: in the UK unleaded handles are normally green and diesel black, but not on every forecourt.
- The first fill in a new vehicle is the time to check the filler flap — inside it, or on the cap, many cars state which fuel to use.
- Mark the key. In a household with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember.
- Before the nozzle comes off the petrol pump the first time you fill a hired or new motor, say "diesel" aloud. Daft, yes, yet it works.
- Thinking about something else is when this becomes an easy mistake to make, and so put the phone away and keep your mind on the pump.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler built to refuse a petrol nozzle, and aftermarket devices exist for the rest. Treat it as a backstop, then keep checking the petrol pump.
- Stop as soon as you realise. Less petrol inside the tank means a thinner mixture. It doesn't change what to do next, which is still not to crank it.
Petrol already in a diesel around Horsham? Start here
The order of things is brief, then. Leave it unstarted, with your ignition off as well. Still at the forecourt, at Sainsbury's or anywhere else? Ask the attendants to help you roll the car clear of the pump. Ring 0333 366 0103 next, with three facts — your fuel, the approximate amount, and whether it has run.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost lubrication, make it a separate issue — Horsham has a page all for it.
One petrol in a diesel job in Horsham costs more than another. Why?
Four different jobs lie behind the four scenarios above — which is why there is no fair single quote. What shifts your cost is chiefly which of them you are in. Two things follow that: the petrol that got in as a share of what the tank holds, then the spot the vehicle is in and whether a van can get to it safely.
Before any quote, not after, come three queries: your fuel that got in, its quantity, and if it has run. That is why. With the replies, you get a straight figure instead of a range.
About Horsham itself
Horsham is a town situated in the South East of England, on the River Arun in West Sussex, with The Common and New Town being nearby areas. Horsham has a population of around 23,031 people and is characterized by a significant proportion of flat housing. Horsham is located approximately 32 miles from London and 18 miles from Brighton and Hove, making it a commuter town with a relatively low elevation of 49 metres. Horsham's riverside setting contributes to its geographical identity.
Across West Sussex and around Horsham: fuel drain cover
Petrol in diesel jobs around Horsham — part of the RH postcode area — go to teams that likewise cover the spots round it, The Common, New Town and Oakhill included. A forecourt, a supermarket car park, a lay-by or your own driveway are all places we work, and your car doesn't need to move to us.
At the petrol pump around Horsham, right now?
In that case, you could not be in a better spot. Keep it off. Call.