How Worried Should You Be? Petrol in a Diesel Car in Waverley
Not started? Then less worried than you probably are. Everyone around Waverley starts with "have I wrecked it?", and the honest answer is usually no: petrol left inside your tank of a diesel remains harmless until priming, cranking or driving draws it into the fuel system. Petrol in Diesel is who to phone, with your motor kept off, so it stays that way. What petrol really does to a diesel, how to gauge how far it's travelled, and how to keep it from happening a second time: that is the rest of this page.
Petrol in a diesel: what does it do to the motor?
Two tasks fall to diesel on its route through a motor. Before it ignites, it protects — and then it burns. Very fine gaps are built into your injectors and your high-pressure pump, and just the diesel flowing through stops those surfaces grinding together.
Poorly at the first, not at all at the second: that is petrol. It's thinner than diesel and removes the lubrication the system rests on, so a pump running on a petrol mix is a pump wearing itself. And petrol is made to resist igniting under compression, which is the reverse of what a diesel needs from its fuel. That is where the rattling comes from.
Put those together and the shape of the problem is plain. Not contact but movement is what causes the harm. Where that petrol is only in your tank, it is an issue of fuel, nothing more. A pump that has been running on that petrol is the start of a mechanical one, and whatever a worn pump sheds travels on with your fuel to the injectors downstream.
Four situations we see in Waverley: how bad is petrol in a diesel?
The best case there can be: filled up, not once started. Being at a forecourt is what makes this possible: elsewhere, the vehicle has been driven there to begin with. With that petrol held in your tank alone, it is drained and flushed on the spot, and nothing more is needed.
A moment's running, or just your ignition on. Once primed, the system has pulled petrol from that tank up to the filter and the fuel lines. Still usually simple: drain, flush, and your filter dealt with.
Driven a few miles. Now the pump has spent these miles running on weakened fuel. How hard your car was driven counts as much as how far, and the work takes in the tank, your lines, the filter and fresh fuel through the whole circuit. On the school run to the local primary school, the distance is small. A run as far as Edinburgh, under 10 miles away, is a very different job. So is any mileage on the M8, under 10 miles from Waverley, where the engine has been running hard the whole time.
Driven on until it protested — rattling, smoke, a lumpy idle, a dead throttle. The fuel isn't behaving like diesel any more, and the motor is saying so. Stop wherever you are — the verge on Waverley Road, a lay-by, a side street — and leave the vehicle there. Lasting damage is very unusual when a vehicle is stopped quickly, and the fuel drain and flush that still go first deal with it.
What Waverley people get told about petrol in a diesel — and the stories in it
Myth: topping up to full with diesel makes it fine. It does not. Nothing is removed by topping up — you are left with a bigger tank, still the same mixture. A diesel fuel system does not tolerate petrol by percentage in the way that advice assumes.
If anything, the opposite holds. Myth: "A newer diesel can cope with a bit of petrol." More precise parts and higher pressure are how a current diesel runs its fuel, and that makes the protection count more, not less.
The myth that catches drivers out: if it starts and drives, it must be unharmed. Diesel in a petrol motor normally means a motor that will not run: the driver stops, and so does the harm. A diesel fed petrol normally starts, ticks over and drives away as if nothing has happened, whilst your pump grinds. Fine and running are not the same thing.
An old workaround for a distinct issue lies behind this one. Myth: "Add some two-stroke oil and drive the car home." What petrol has thinned remains weakened, and the petrol stays inside that tank regardless.
Once the motor has been run, part of that petrol is in the filter and the lines, not your tank — and your next start pulls it right back through your pump. So the myth "drain the tank yourself and you are sorted" doesn't stand up. Also, a can of petrol drained at the kerbside is genuinely risky.
Petrol in a diesel: how does it happen?
It's seldom carelessness, and no one does it on purpose. The petrol nozzle is the smaller of the two and slips into a diesel filler with almost no resistance; a diesel nozzle generally won't go into a petrol vehicle at all. The forecourt makes it easy, and the mistake runs one way.
The moment routine stops matching the vehicle is the moment it occurs. Courtesy car, hire car, or a vehicle that's new. Households running one of each, petrol and diesel. A forecourt you know, but with its pumps laid out differently. Racing for a train at Eskbank and filling up en route. Years of petrol cars behind you, a diesel Volkswagen Passat in front of you at the forecourt for its first tank — that's when. With rain, a call arriving, or a car full of children to deal with, your hand simply does what it has always done.
Waverley people: how to prevent petrol in a diesel next time
- A green handle for unleaded and black for diesel is normal in the UK — yet not on every forecourt. Trust the label on the petrol pump, not the colour.
- Many vehicles state the fuel type inside the filler flap or on the cap, so check it on the first fill in any vehicle you don't know.
- Mark the key. In a house with one of each, a coloured fob or a sticker on your diesel's key does more than any amount of meaning to remember.
- "Diesel", aloud, before you pick up the nozzle — every time a new or hired car gets its first tank. It sounds silly. It works.
- Thinking about something else is when this becomes an easy mistake to make, and so tuck your phone away and keep your mind on the petrol pump.
- A misfuel inhibitor helps, up to a point. Some diesels have a filler built to reject a petrol nozzle, and add-on devices are available for motors without one. They are a backstop, not a reason to stop checking the petrol pump.
- As soon as you realise, stop: less petrol inside your tank means a weaker mixture. What to do next doesn't change, though — still do not fire it up.
Waverley: already put petrol in a diesel?
In that case, there is only a short order of things. Leave it unstarted, with your ignition switched off too. Ask the attendants to help you push it clear of the pump if you're still at the forecourt, whether that is Tesco or somewhere else. Next, 0333 366 0103. We'll ask what was put in, about how much, and if it's been run.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost protection, make it a different problem — Waverley has a page all for it.
One petrol in a diesel task around Waverley costs more than another. Why?
Four different jobs lie behind the four scenarios above — which is why there's no fair single quote. Which of them you're in is chiefly what moves the cost. Two things come after that: the petrol that went in as a proportion of what your tank holds, then the spot your car is in and whether a technician can reach it safely.
What got in, how much, and if it's run — three questions our engineers ask before quoting, not after, for precisely that reason. A range becomes a straight figure once the replies are in.
About Waverley, for a moment
Waverley is a suburban area situated on the riverside in Midlothian, with a mix of semi-detached housing and other residential properties. Waverley lies close to the city of Edinburgh, approximately 6.4 miles from the city centre, and is near other local places such as Lasswade and Eldindean. Waverley has a population of around 6144 people and is located at an elevation of 93 metres. Waverley is also relatively distant from London, at a distance of 325.4 miles.
Fuel drain cover across Midlothian, Waverley included
Petrol in diesel call-outs in Waverley — part of the EH postcode area — go to teams that likewise cover the locations round it, Lasswade, Eldindean and Quarryhead included. The vehicle doesn't need to come to us: we drain on a forecourt, in a supermarket car park, in a lay-by or on your own driveway.
Waverley: still at the pump?
Then, you could not be in a better spot. Ring, and leave it turned off.