How Worried Should You Be? Petrol in a Diesel Car in Round Spinney
Far less than you probably are, if it has not been started. Till the ignition primes your pump, your starter turns, or your car is driven, petrol in a diesel tank simply sits there and does no harm. Which makes the truthful reply to the first Round Spinney query — "have I wrecked it?" — normally no. Leave the engine off and ring Petrol in Diesel — that is how you keep it like that. Read on for three things: the effect petrol has inside a diesel motor, the clues of how far it has got, and ways to make sure you never repeat it.
What petrol in a diesel does to the motor
Diesel has two jobs on its way through an engine. Lubricating comes before burning; it does both. Built to extremely fine tolerances, the fuel injectors and the pump rely on your diesel flowing through them to keep their surfaces from wearing against one another.
Badly at the first, not at all at the second: that's petrol. Being less viscous than diesel, petrol strips out the protection a fuel system needs, so a pump on the blend to wear itself. It's also made to resist igniting under compression — the reverse of what a diesel needs — which is why you get the clattering.
The shape of the problem is clear once you put those together. It is movement that causes the harm, not contact. Where that petrol is only in the tank, it's an issue of fuel, nothing more. Once the pump has been working on that petrol, a mechanical problem has begun: whatever is shed by a pump that is wearing down travels downstream to your injectors with your fuel.
Petrol in a diesel around Round Spinney: how bad is it? Four situations
Filled up, not once started. The best case there is. That petrol is in that tank and just that tank, and the job is a drain and a flush where the vehicle stands. This is the one scenario that can only truly occur at a forecourt, as anywhere else the vehicle has been driven to get there.
Ignition on, or started for a moment. With the system primed, the lines and filter now contain petrol that came from the tank. That is generally still a simple task — a drain, a flush, and the filter dealt with.
Driven a couple of miles. Now the pump has spent these miles working on thinned fuel. The work is your tank, the lines, the filter and clean fuel through the whole circuit, and how hard the vehicle was driven matters as much as how far. On the school run to Thorplands Primary School, the mileage is short. Any miles on the M1, under 10 miles from Round Spinney, means your engine has worked hard throughout, and a run to Milton Keynes, under 25 miles away, is a very different job as well.
Driven on until it protested — knocking, smoke, a lumpy idle, a dead throttle. The motor is telling you your fuel is no longer acting like diesel. Stop where you are — on the verge on North Portway Close, at the kerb, down a side road — and do not move it again. A car stopped quickly very seldom has lasting damage, because the fuel drain and the flush, which still come first, deal with it.
What Round Spinney motorists get told about petrol in a diesel — and the stories in it
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Nothing is removed when you top up — your tank just carries more of the same mixture. The assumption behind the advice — that diesel fuel systems accept petrol by percentage — is wrong.
"Current diesels can handle a little petrol" — a myth, and closer to the opposite. More precise parts and higher pressure are how a current diesel runs its fuel, and that makes the protection count more, not less.
This is the one that catches drivers. Myth: "If it starts and drives, there is no harm done." The motorist of a petrol motor fed diesel normally stops, since it will not run, and the harm stops there. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile the pump wears. Running is not the same as fine.
Myth: "Add some two-stroke oil and drive it home." It's an outdated fix for a distinct fault. None of what petrol weakened is put back by it — and later, that tank still contains the petrol.
The next start sends petrol back round your pump out of the fuel lines and your filter, where some of it sits once the motor has been run. That's why draining the tank yourself does not leave you sorted — a myth. It's also genuinely risky to drain petrol into a can at the roadside.
How petrol ends up: petrol in a diesel
Nobody does it on purpose, and it's rarely carelessness. A diesel nozzle mostly will not fit a petrol car, yet the slimmer petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one mistake simple, and just in one direction.
Habit and the vehicle getting out of step is how it takes place. A new vehicle, a hire car or a courtesy car. Two cars on one drive, one petrol, one diesel. The pumps in a different order on a well-known forecourt. Racing for a train outside Northampton and filling up en route. Exactly the moment it takes place: after years of driving petrol, a driver fills a diesel Volkswagen Golf for the first time. With rain, a call coming in, or a car full of children to deal with, the hand simply does what it always has.
Next time you fill up around Round Spinney: avoiding petrol in a diesel
- Check the petrol pump, not the colour. In the UK unleaded handles are usually green and diesel black, but not on every forecourt. The label is what counts.
- Many motors state the fuel type inside your filler flap or on the cap, so check there on the first fill in any motor you don't know.
- Label your key. In a household with one of each, a coloured fob or a sticker on the diesel's key does more than any amount of intending to remember.
- It sounds silly and it does the trick: on your first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the petrol pump.
- Mistakes like this are easy to make while your mind is on something else, so your phone goes away.
- Up to a point, a misfuel inhibitor helps: some diesels have a filler built to reject a petrol nozzle, and add-on devices are available for the remainder. Count it as a safety net, then keep reading the petrol pump.
- Stop as soon as you realise. Less petrol inside your tank means a weaker mix. It doesn't change what to do next, which is still not to start it.
Put petrol in a diesel in Round Spinney already?
Then the order of things is short. Don't crank it, and do not switch the ignition on. Yet at the forecourt, at Shell or anywhere else? Ask the staff to help you push it clear of the petrol pump. Then phone 0333 366 0103 and tell us what went in, about how much, and whether it's run.
Say so if it was AdBlue rather than petrol: it's a different issue, with its own page for Round Spinney, since AdBlue brings corrosion and deposits rather than lost protection.
What makes one Round Spinney petrol in a diesel job cost more than the next
The four situations above are four different tasks, so no single price for this would be fair. Which of them you're in is chiefly what shifts the cost. Next it is the ratio — how much petrol got in against how much that tank takes — and then where the vehicle is and whether a van can get to it safely.
What went in, how much, and if it has run — three questions our engineers ask before pricing, not after, for precisely that reason. Those answers change a range into a straight figure.
About Round Spinney itself
Round Spinney is a suburban area in Northamptonshire, situated inland at an elevation of 92 metres, and is located near the cities of Milton Keynes and Northampton. Round Spinney sits within a network of residential areas, including Southfields, Thorplands, and Goldings, and is characterized by its predominantly detached housing stock. Round Spinney is also relatively close to London, being approximately 61 miles northwest of the capital city.
Fuel drain cover across Northamptonshire, Round Spinney included
Petrol in diesel call-outs in Round Spinney — part of the NN postcode area — go to teams that also cover the places round it, Southfields, Thorplands and Goldings included. No need to bring the car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all locations where we work.
Still at the petrol pump around Round Spinney?
The best position there is, then — that's where you are. Ring, and leave it turned off.