Petrol in a Diesel Car in Kings Muir: How Worried Should You Be?
Far less than you probably are, provided it has not been started. Until your ignition primes the pump, your starter cranks, or your car is driven, petrol in a diesel tank simply waits there and does nothing. Which makes the truthful reply to that first Kings Muir question — "have I ruined it?" — normally no. Leave your engine off then call Petrol in Diesel — that is how you keep it like that. 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 your engine
Passing through a motor, diesel does two things at once. Before it burns, it protects — then it combusts. Made to extremely fine tolerances, your injectors and the pump depend on the diesel moving through them to keep their surfaces from wearing against one another.
Badly at the first, not at all at the second: that is petrol. The knocking comes from petrol being made not to ignite when compressed, which is precisely the reverse of what a diesel needs. On top of that it is runnier than diesel, it strips away the lubrication the system hinges on, and any pump running on such a mixture is wearing itself.
Together, those leave the shape of the issue clear. It's circulation that does the damage, not contact. Any tank with petrol in it is a fuel problem. Whatever a worn pump sheds travels on, borne by the fuel, into the fuel injectors further along, which is why a pump that has worked on that petrol is where a mechanical fault begins.
Four situations our engineers see in Kings Muir: how serious is petrol in a diesel?
The best case there is: filled up, never started. At a forecourt, and really only there, the petrol is still limited to that tank — since anywhere else your car was driven to reach it. The job is emptying and flushing on the spot.
A brief spell of running, or merely the ignition on. Petrol has left the tank and got to the filter and your lines, since your system has been primed. Still usually straightforward: drain, flush, and the filter seen to.
Driven a few miles. Now your pump has spent these miles working on diluted fuel. Miles is only half of that; how hard it was driven matters just as much. Either way the work includes that tank, your lines, your filter and fresh fuel through the entire circuit. Short trips, like the school run to the local primary school, are one thing. A run as far as Edinburgh, under 25 miles away, is a very different job. So is any distance on the M8, under 25 miles from Kings Muir, where the engine has been labouring hard throughout.
Driven until it protested. Knocking, a ragged idle, smoke, a throttle that has gone soft. The fuel isn't behaving like diesel any more, and the engine is telling you. Pull up on the spot — on the verge on Craigerne Lane, at the kerb, down a side road — and don't move it again. Permanent damage is very unusual when a car is pulled over early, and the drain and flush-through that still go first sort it out.
Petrol in a diesel myths Kings Muir drivers hear
"Top it up the rest of the way with diesel and it'll be fine" — a myth. It won't. Nothing is removed by topping up — you're left with a bigger tank, still the same mix. That advice presumes a diesel fuel system tolerates petrol by percentage. It doesn't.
If anything, the reverse is true. Myth: "A current diesel can cope with a bit of petrol." At higher pressure, through finer components: that's how a current diesel handles its fuel, and so the lubrication matters for more, not less.
This is the one that fools motorists. Myth: "If it starts and drives, there is no damage done." Diesel in a petrol motor normally leaves a motor that will not run: the motorist stops, and so does the damage. A diesel fed petrol usually starts, idles and drives away as though nothing has happened, whilst your pump grinds. Being able to run isn't proof of being fine.
Myth: a two-stroke additive makes it safe to drive home. It was an old fix, meant for another fault. What petrol has weakened remains diluted, and the petrol remains inside your tank regardless.
Myth: "Drain that tank yourself and you are sorted." After the engine has run, some of that petrol is no longer inside that tank: it's in the filter and the fuel lines, and it goes straight back through your pump at the next start. Emptying petrol into a can by the roadside is also genuinely risky.
Petrol in a diesel: how does it take place?
Nobody does it on purpose, and it's rarely carelessness. One way only, since of the nozzles: the narrower petrol one slips inside a diesel filler with almost no resistance, while the diesel one generally will not fit a petrol vehicle. That's how the forecourt makes it straightforward.
Routine and the vehicle getting out of step is when it takes place. Hire cars, courtesy cars, and cars that are new to you. Households running one of each, petrol and diesel. The pumps in a different order on a well-known forecourt. A train to catch, and a rushed fill en route to the nearest station. Exactly the moment it occurs: after years of driving petrol, someone fills a diesel Volkswagen Golf for the first time. Add a back seat full of kids, a phone call or rain, and the hand wins.
Next time you fill up in Kings Muir: preventing petrol in a diesel
- Green for unleaded and black for diesel is normal in the UK — yet not on every forecourt. Go by the label on the petrol pump, not the colour.
- The first fill in a new motor is the time to check the filler flap — on it, or on the cap, many vehicles state the fuel to use.
- Good intentions count for less than a sticker or a fob in a vivid colour on the diesel's key if a household has one of each. So mark it.
- Before the nozzle comes off the petrol pump the first time you fill a hired or new car, say "diesel" aloud. Daft, yes, but it does the trick.
- 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 petrol pump.
- Some diesels have a filler built to block a petrol nozzle, and devices you can add are available for motors without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop checking the pump.
- Stop as soon as you realise. Less petrol inside the tank means a thinner blend. It does not change what to do next, which is still not to fire it up.
Put petrol in a diesel in Kings Muir already?
Then the order of things is brief. Leave it unstarted, with your ignition off too. Ask the attendants to help you roll it away from the pump if you're still on the forecourt, whether that is BP or anywhere else. Phone 0333 366 0103 next, with three facts — your fuel, the rough volume, and if it's run.
Say so if it was AdBlue rather than petrol: it is a different issue, with its own page for Kings Muir, because AdBlue brings corrosion and deposits instead of lost lubrication.
Kings Muir petrol in a diesel tasks: why one costs more than another
There is no fair single price for this, since the four situations above are four separate jobs. Chiefly, the cost shifts with which one you're in. The ratio counts next, meaning how much of the tank is petrol, and then the position of the vehicle and whether reaching it is safe for a technician.
Ahead of any quote, not after, come three questions: the fuel that went in, the quantity, and whether it's run. That is why. A range becomes a straight figure when the replies are in.
About Kings Muir, briefly
Kings Muir is a suburban area situated on the riverside in the Scottish Borders, with an elevation of 191 metres. Kings Muir lies approximately 21 miles southeast of Edinburgh and 312 miles north of London, near the communities of Craigerne and Kings Meadows. Kings Muir is characterised by its predominantly detached housing stock, reflecting its suburban nature. Kings Muir has a population of around 2487 residents, according to recent estimates.
Fuel drain cover across Scottish Borders, Kings Muir included
Petrol in diesel jobs in Kings Muir — part of the EH postcode area — go to vans that also cover the locations round it, Craigerne, Craigerne Cottage and Kings Meadows included. We drain wherever the car is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
At the pump around Kings Muir, still?
Then you are in the best place there can be. Switched off it remains; then ring.