Petrol in a Diesel Car in Cosford: How Worried Should You Be?
Far less than you probably are, if it hasn't been started. "Have I ruined it?" is the first thing everyone around Cosford asks, and the honest answer is generally no, since petrol left in a diesel tank harms nothing till it is drawn through the system — by ignition priming, by the starter, or by being driven. Petrol in Diesel is who to call, with your motor kept off, so it remains that way. The rest of this page explains what petrol really does to a diesel, how to judge how far it has got, and how to make sure it does not happen to you a second time.
Inside your engine: what petrol in a diesel really does
Two tasks fall to diesel on its journey through a motor. It lubricates to begin with, and after that does it burn. Extremely fine tolerances are built into the fuel injectors and the high-pressure pump, and just the diesel flowing through keeps those surfaces from grinding together.
The second job petrol doesn't do at all, and the first it does poorly. It's runnier than diesel and takes away the protection the fuel system hinges on, 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's where the clattering comes from.
Put these together and the shape of the problem is plain. Not contact but circulation is what does the harm. All a tank with petrol in it amounts to is a fuel problem. A pump that has been working on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds travels on with your fuel to the fuel injectors further on.
How bad is petrol in a diesel? Four scenarios our engineers see around Cosford
Fuelled up, never started. The best case there is. Only that tank has petrol in it, and so the job is clearing that tank and purging the system where the car stands. This scenario can only truly happen at a forecourt: anywhere else, your car got there by being driven.
The ignition switched on, or a short start. Once primed, the fuel system has pulled petrol from the tank as far as the fuel filter and your lines. Usually nothing more than emptying, cleaning and seeing to your filter, and so still simple.
Those few miles driven were your pump labouring on fuel diluted by petrol the whole way. How hard the vehicle was driven matters as much as how far, and the work takes in the tank, your lines, the fuel filter and clean fuel through the entire circuit. On the school run to The Griffin Primary School, the miles is short. Driving as far as Coventry, under 15 miles away, makes a very different task — as does any mileage on the M6, under a mile from Cosford, with the engine working hard all the way.
Rattling, an uneven idle, smoke, a throttle gone soft: driven until it complained. That's the engine telling you its fuel no longer is behaving like diesel. Stop on the spot — on the verge on Cosford Lane, at the kerb, down a side road — and don't move it again. The fuel drain and flush-through still come first, and they deal with it: when a car is pulled over soon, lasting damage is very unusual.
What Cosford motorists get told about petrol in a diesel — and the myths in it
Myth: "Fill it the rest of the way with diesel and it'll be fine." It will not. Nothing comes out when you top up — that tank simply holds more of the same blend. The idea behind the advice — that diesel fuel systems accept petrol by percentage — is wrong.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the reverse. At higher pressure, through more precise parts: that is how a modern diesel handles its fuel, and so the lubrication matters for more, not less.
The myth that catches people out: if it starts and drives, it must be unharmed. Any petrol motor fed diesel normally won't run, and so the motorist stops and the harm stops with them. Whilst the pump grinds, a diesel fed petrol usually starts, ticks over and drives away as though nothing has happened. Fine and running aren't the same thing.
Myth: "Add some two-stroke oil and drive the vehicle home." It's an outdated workaround for a different issue. It doesn't put back what petrol has thinned, and that petrol is still inside that tank later.
"Drain it yourself and you're sorted" — a myth, since after it has been running some petrol lies in the fuel filter and lines, waiting to go right back through the pump at your next start. Clearing petrol into a can by the kerbside is also truly hazardous.
Petrol in a diesel: how does it take place?
It is rarely carelessness, and no one does it on purpose. One way only, because 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 simple.
The moment routine stops matching the vehicle is the moment it occurs. Hire cars, courtesy cars, and motors that are new to you. Households running one of each, petrol and diesel. The pumps in a different order on a well-known forecourt. Racing for a train outside Rugby 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 just does what it has always done.
Preventing petrol in a diesel next time you fill up in Cosford
- The label is what counts, so check the pump rather than the colour: in the UK unleaded handles are usually green and diesel black, but not on each forecourt.
- Plenty of motors state the fuel type inside the filler flap or on the cap, so check it on the first fill in any motor you do not know.
- One of each in the house? Label your key to your diesel — a coloured fob, a sticker — because meaning to remember is not enough.
- "Diesel", aloud, before you pick up the nozzle — every time a new or hired car needs its first tank. It seems daft. It does the trick.
- Put your phone away. This is an easy mistake to make while you're thinking about something else.
- Some diesels come with a filler built to block a petrol nozzle, and devices you can add exist for motors without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop reading the pump.
- Stop the moment you notice. Less petrol inside that tank makes a thinner mix. It doesn't change what to do next, which is still not to start the vehicle.
Petrol already in a diesel in Cosford? Begin here
The order of things is brief, then. Don't switch the ignition on, and do not fire it up. Still on the forecourt, at BP or anywhere else? Ask the staff to help you roll the car away from the pump. Next, 0333 366 0103. We will ask what went in, roughly how much, and if it has been run.
AdBlue, not petrol? Then tell us. Corrosion and deposits, not lost protection, make it a different fault — Cosford has a page just for it.
Why one petrol in a diesel task around Cosford costs more than another
Four separate jobs lie behind the four scenarios above — which is why there's no fair single quote. The situation itself does most of the work of moving your cost. Where your car is counts too, and whether our van can safely get to it, after the proportion of petrol to what that tank holds.
Three questions come first, before quoting, instead of after — what went in, how much, has it run — and that is the reason. A range turns into a straight figure once the replies are in.
About Cosford itself
Cosford is a small hamlet in Warwickshire, situated on the riverside at an elevation of 96 metres, with detached housing being the predominant type of accommodation. Cosford lies near the cities of Coventry and Rugby, and is close to nearby places such as Churchover and Harborough Magna. Cosford is located in the West Midlands region, approximately 78.9 miles northwest of London. Cosford has a population of around 556 people, according to recent estimates.
Across Warwickshire and around Cosford: fuel drain cover
Our vans answering petrol in diesel call-outs around Cosford, in the CV postcode area, also work the spots near it, Churchover, Harborough Magna and Brownsover included. No need to move your car to us. Forecourts, supermarket car parks, lay-bys and your own driveway are all places where we work.
In Cosford and still at the petrol pump?
Then you're in the best spot there can be. Call, and keep it switched off.