Kingsknowe: Petrol in a Diesel Car? How Worried to Be
Less than you probably are, provided it hasn't been started. "Have I wrecked it?" is the first thing everyone in Kingsknowe asks, and the truthful answer is generally no, since petrol left in a diesel tank hurts nothing till it's drawn through the system — by ignition priming, by the starter, or by being driven. Leave the engine off then call Petrol in Diesel — that keeps it like that. The remainder of this page covers 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 engine
On its way through a motor, diesel does two tasks. Lubricating comes before burning; it does both. Extremely fine clearances are built into the fuel injectors and the high-pressure fuel pump, and just the diesel flowing through keeps those surfaces from grinding together.
Of those two tasks, petrol handles the first poorly and the second not at all. It's runnier than diesel and removes the lubrication your fuel system depends on, and so a pump running on a petrol mix is a pump wearing itself. And petrol is designed to resist igniting under compression, which is the reverse of what a diesel needs from its fuel. That is where the clattering comes from.
Taken together, they make clear what shape the trouble takes. The damage is done by movement, not by contact. Petrol in a tank is a fuel fault. After your pump has been working on that petrol, a mechanical issue has started: anything shed by a pump that is wearing is carried downstream to your injectors with the fuel.
Four situations our engineers see around Kingsknowe: how bad is petrol in a diesel?
Filled up, and never started: no case is better. Being at a forecourt is what makes this the case: elsewhere, the car has been driven there to begin with. With that petrol kept inside that tank alone, it is cleared and rinsed right where it stands, and nothing more is needed.
Ignition on, or started for a moment. Once primed, the system has pulled petrol out of that tank up to the fuel filter and the fuel lines. Drain, flush, see to the filter: still normally easy.
Some miles driven, and the pump has spent each of them working on thinned fuel. Miles is only half of it; how hard it was driven counts equally. Either way the work runs to that tank, your lines, your filter and fresh fuel through the entire system. Short trips, like the school run to the local primary school, are one matter. Getting as far as Edinburgh, under 5 miles away, makes a very different job — as does any distance on the M8, under 3 miles from Kingsknowe, with your engine labouring hard the whole time.
Knocking, a ragged idle, smoke, a throttle gone soft: driven till it complained. That's your engine telling you its fuel no longer is behaving like diesel. Pull up wherever you are — the verge on Kingsknowe Road South, a lay-by, a side street — and leave the car where it is. Permanent damage is very uncommon if a vehicle is stopped early, and the drain and flush-through that still go first deal with it.
Petrol in a diesel myths Kingsknowe motorists hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Nothing is removed when you top up — that tank just holds more of the same blend. Percentage isn't how a diesel fuel system tolerates petrol, however much that guidance supposes.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the opposite. Lubrication counts more on modern diesels, not less, since their fuel passes through more precise components at higher pressure.
This is the one that catches motorists. Myth: "If it starts and drives, there's no damage done." Diesel in a petrol motor usually leaves a motor that won't run: the motorist stops, and so does the harm. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually does; meanwhile the pump grinds. Running doesn't mean fine.
Myth: "Add some two-stroke oil and drive it home." It's an old workaround for a distinct fault. It doesn't put back what petrol has diluted, and the petrol is still inside the tank after that.
Myth: "Drain the tank yourself and you are sorted." Once the motor has been run, some of the petrol is no longer in that tank: it is in your filter and the fuel lines, and it goes right back through the pump at the next start. Also, a can of petrol drained by the kerbside is truly hazardous.
How it happens: petrol in a diesel
It's seldom carelessness, and nobody does it on purpose. The forecourt makes it simple: the petrol nozzle is the narrower of the two, and it slides into a diesel filler with almost no resistance, whilst a diesel nozzle generally won't go into a petrol vehicle at all. So the mistake runs one way.
When habit and the vehicle stop matching, it occurs. Courtesy car, hire car, or a vehicle that is new. A household with one petrol and one diesel on the driveway. The pumps in a different order on a well-known forecourt. A hurried fill en route to the nearest station with a train to catch. A new-to-you diesel Renault Megane, its first fuelling, and a driver accustomed to petrol: precisely when it takes place. Add a back seat full of kids, a phone call or rain, and habit takes over.
How to avoid petrol in a diesel on your next fill-up around Kingsknowe
- Check the pump, not the colour. In the UK unleaded handles are generally green and diesel black, but not on each forecourt. The label is what counts.
- Inspect the filler flap. Plenty of cars state the fuel type inside the flap or on the cap. Look at it on the first fill in any motor you do not know.
- One of each in the household? Label the key to your diesel — a bright fob, a sticker — because intending to remember isn't enough.
- It sounds silly and it works: on the first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the pump.
- Thinking about something else is when this becomes an easy mistake to make, so put your phone away then keep your mind on the pump.
- Add-on devices are available for motors without one, and some diesels are built with a filler that will not take a petrol nozzle. Useful — but a backstop at best, never a reason to stop checking the label.
- As soon as you realise, stop: less petrol in the tank makes a thinner blend. What to do next doesn't change, though — still don't crank it.
Petrol already in a diesel around Kingsknowe? Begin here
Short and simple, then, is the order of things. Leave it unstarted, with the ignition switched off as well. Yet at the forecourt, at Sainsbury's or anywhere else? Ask the staff to help you roll the car away from the pump. Ring 0333 366 0103 next, with three facts — the fuel, the approximate amount, and whether it's run.
If it was AdBlue instead of petrol, say so. That is a separate problem — corrosion and deposits instead of lost protection — and it has its own page for Kingsknowe.
Why one petrol in a diesel job around Kingsknowe costs more than another
There's no honest single price for this, because the four situations above are four different tasks. Which of them you're in is chiefly what moves your cost. The ratio counts next, meaning how much of that tank is petrol, followed by the location of the vehicle and whether reaching it is safe for our van.
That's why our engineers ask three questions before pricing rather than after: what went in, how much, and whether it has run. Those replies are what turn a range into one firm number.
About Kingsknowe
Kingsknowe is a suburban area in the City of Edinburgh, situated near the Water of Leith and overlooking the surrounding countryside. Kingsknowe sits at an elevation of 92 metres, approximately 3.9 miles from Edinburgh city centre. Kingsknowe is characterized by its predominantly flat-type housing and forms part of the larger urban area surrounding Edinburgh. Kingsknowe is close to nearby places such as Longstone, Parkhead, and Juniper Green.
Fuel drain cover across City of Edinburgh, Kingsknowe included
The vans answering petrol in diesel jobs around Kingsknowe, in the EH postcode area, also work the spots near it, Longstone, Parkhead and Juniper Green included. The car doesn't need to move to us: our technicians drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive.
Kingsknowe: still at the pump?
Then, you couldn't be in a better place. Keep the vehicle turned off, then ring.