How Worried Should You Be? Petrol in a Diesel Car in Surbiton
Unstarted? Then less anxious than you likely feel. Everyone in Surbiton starts with "have I ruined it?", and the honest answer is normally no: petrol left in your tank of a diesel stays harmless until priming, cranking or driving draws it into the fuel system. Petrol in Diesel is who to ring, with your motor left off, and so it stays that way. Below, this page sets out what petrol actually does inside a diesel, how far it may have gone, and how to stop it happening to you again.
Inside your engine: what petrol in a diesel does
Diesel has two jobs on its way through a motor. Before it combusts, it lubricates — then it ignites. What stops the surfaces inside the high-pressure fuel pump and your injectors from wearing down against one another is your diesel passing through them — they are made to very fine clearances.
The second task petrol doesn't do at all, and the first it does poorly. The rattling comes from petrol being made not to ignite when compressed, which is exactly the reverse of what a diesel needs. On top of that it is runnier than diesel, it strips away the lubrication the fuel system depends on, and any pump working on such a blend is wearing itself.
Put these together and the shape of the trouble is clear. Contact doesn't do the harm — circulation does. A tank with petrol in it is a fuel fault. A pump that has been working on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds moves on with your fuel to your injectors downstream.
How serious is petrol in a diesel? Four situations our technicians see around Surbiton
The best case there is: filled up, not once started. Only your tank has petrol in it, and so the job is clearing the tank and purging your system where the car stands. This situation can only really occur at a forecourt: anywhere else, your car got there by being driven.
A brief spell of running, or just the ignition on. With the fuel system primed, the fuel lines and filter now hold petrol that has come from the tank. Still normally straightforward: drain, flush, and the filter dealt with.
Those few miles on the road were your pump running on fuel weakened by petrol throughout. The work is that tank, your lines, your filter and fresh fuel through the whole circuit, and how hard the vehicle was driven counts as much as how far. Short trips, such as the school run to Lime Tree Primary School, are one thing. Driving as far as Westminster, under 15 miles away, makes a very different task — as does any mileage on the M3, under 10 miles from Surbiton, with the motor running hard the whole time.
Driven on till it protested — rattling, smoke, a lumpy idle, a soft throttle. What you are hearing is the motor reporting fuel that no longer runs like diesel. Whether it's the verge on Ewell Road, a lay-by or a side road, stop where you are then leave it. The drain and flush still go first, and they sort it out: if a vehicle is stopped soon, lasting damage is very rare.
Myths Surbiton motorists hear about petrol in a diesel
False: 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. A diesel fuel system doesn't accept petrol by percentage in the way that advice supposes.
If anything, the reverse holds. Myth: "A current diesel can cope with a bit of petrol." At higher pressure, through more precise components: that is how a current diesel handles its fuel, so the lubrication counts for more, not less.
The myth that catches people out: if it starts and drives, it must be unharmed. The driver of a petrol engine fed diesel usually has no choice but to stop, since it will not run, and the harm stops there. A diesel fed petrol normally starts, ticks over and drives away as if nothing has happened, whilst the pump grinds. Running doesn't mean fine.
"A drop of two-stroke oil and drive it home" — a myth, borrowed from a fix from years ago, for a different fault. None of what petrol weakened gets put back by it — and afterwards, that tank still contains that petrol.
Once your engine has been run, part of that petrol is in the filter and your lines, not that tank — and the next start pulls it right back through your pump. So the myth "drain the tank yourself and you are sorted" does not hold. On top of that, petrol cleared into a can by the road is genuinely hazardous.
How it happens: petrol in a diesel
It's seldom carelessness, and nobody does it on purpose. The forecourt makes it easy: the petrol nozzle is the narrower 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 car at all. So the error runs one way.
The moment routine stops matching the vehicle is the moment it happens. Hire cars, courtesy cars, and motors that are new to you. Households running one of each, petrol and diesel. A familiar forecourt with the pumps in a different order. A train to catch, and a hurried fill en route to the nearest station. A new-to-you diesel Volkswagen Passat, its first fuelling, and a motorist used to petrol: precisely when it happens. The hand repeats what it has always done once you add rain, a phone call or a back seat full of kids.
Next time you fill up in Surbiton: avoiding petrol in a diesel
- The label is what matters, and so check the petrol pump instead of the colour: in the UK unleaded handles are normally green and diesel black, but not on each forecourt.
- Many cars state the fuel type inside your filler flap or on the cap, so check there on your first fill in any car you do not know.
- One of each in the home? Label your key to your diesel — a bright fob, a sticker — since meaning to remember is not enough.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the petrol pump. It seems silly and it does the trick.
- Whilst you're thinking about something else, this is an easy mistake to make — so put your phone away.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler designed to refuse a petrol nozzle, and add-on devices are available for the rest. Count it as a safety net, and keep reading the petrol pump.
- As soon as you realise, stop: less petrol in that tank means a thinner blend. What to do next doesn't change, though — still don't fire it up.
Already put petrol in a diesel in Surbiton?
In that case, there is only a short order of things. Never fire it up, and do not switch your ignition on. If you are still at the forecourt — Esso or anywhere else — ask the staff to help you push it away from the pump. Next, 0333 366 0103. We'll ask what got in, roughly how much, and if it has been run.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost lubrication, make it a different fault — Surbiton has a page just for it.
What makes one Surbiton petrol in a diesel task cost more than the next
The four scenarios above are four separate jobs, so no single price for this would be honest. What moves your cost is mostly which of them you're in. The share counts next, meaning how much of the tank is petrol, and then the location of your car and whether getting to it is safe for a technician.
Three queries come first, before quoting, instead of after — what was put in, how much, has it run — and this is the reason. Their replies are what turn a range into one firm number.
About Surbiton and its setting
Surbiton is a locality in the Royal Borough of Kingston upon Thames, situated approximately 10.8 miles from central London. Surbiton sits at an elevation of around 39 metres, near the River Thames and close to nearby places such as Seething Wells and Berrylands. Surbiton is predominantly composed of flat dwellings, reflecting its urban character. Surbiton has a population of around 7148 people, according to recent estimates.
Fuel drain cover across Greater London, Surbiton included
Surbiton rests in the KT postcode area, and the vans that answer petrol in diesel jobs there work the spots near it as well — Seething Wells, Berrylands and Southborough among them. Our engineers drain where the vehicle is — your own drive, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
In Surbiton and still at the petrol pump?
Then, you could not be in a better spot. Keep it off. Phone.