Petrol in a Diesel Car in Old Sarum: How Worried Should You Be?
Less than you likely are, if it has not been started. Till the ignition primes your pump, the starter cranks, or your vehicle is driven, petrol in a diesel tank just sits there and does nothing. Which makes the honest reply to that first Old Sarum question — "have I ruined it?" — normally no. To leave the vehicle like that, call Petrol in Diesel then leave your engine alone. Further down, this page sets out what petrol really does inside a diesel, how far it may have got, and how to stop it happening to you again.
The engine and petrol in a diesel: what happens
On its way through an engine, diesel does two tasks. Before it ignites, it protects — then it burns. The high-pressure fuel pump and the injectors are made to extremely fine tolerances, and the diesel passing through them is what keeps those surfaces from wearing against one another.
Petrol does the first task poorly and the second not at all. The clattering comes from petrol being designed not to ignite when compressed, which is precisely the opposite of what a diesel needs. On top of that it is runnier than diesel, it strips away the lubrication the fuel system rests on, and any pump running on that blend is wearing itself.
Combined, those leave the shape of the problem clear. It is movement that causes the damage, not contact. Where that petrol is only in the tank, it's a fault of fuel, nothing more. After the pump has been labouring on that petrol, a mechanical issue has begun: anything shed by a pump that is wearing travels onward to your injectors with your fuel.
How serious is petrol in a diesel? Four scenarios our engineers see around Old Sarum
Fuelled, and not started: no case is better. Being on a forecourt is what makes this the case: elsewhere, your car has been driven there to begin with. With that petrol held in your tank alone, it is drained and cleaned right where it stands, and nothing more is needed.
A brief spell of running, or merely your ignition on. Once primed, your system has pulled petrol from your tank up to the filter and your lines. Still generally simple: drain, flush, and the fuel filter sorted.
The pump has spent a few miles on thinned fuel — that's what driving it meant. How hard the vehicle was driven counts as much as how far, and this work takes in the tank, the fuel lines, the fuel filter and clean fuel through the whole circuit. The school run to Old Sarum Primary School is one matter. Driving as far as Salisbury, under 3 miles away, makes a very different task — as does any mileage on the M27, under 25 miles from Old Sarum, with the motor labouring hard all the way.
Knocking, an uneven idle, smoke, a throttle gone soft: driven till it complained. The engine is telling you the fuel is no longer behaving like diesel. Leave it where it stops: a lay-by, a quiet street, the verge on Portway. A vehicle pulled over soon very seldom has permanent damage, as the fuel drain and the flush-through, which still go first, sort it out.
Old Sarum people and that petrol in a diesel stories they hear
False: topping up to full with diesel makes it fine. It does not. A fuller tank of the same mixture is all it gives, since topping up takes out nothing. A diesel fuel system doesn't tolerate petrol by percentage in the way that advice presumes.
Myth: a current diesel copes with a bit of petrol. If anything, the reverse. A modern diesel runs its fuel through smaller components at higher pressure, which makes the protection matter more, not less.
"It starts, it drives, and so no harm done" — the myth that catches most people than any other. The motorist of a petrol motor fed diesel usually stops, because it will not run, and the damage stops with them. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile your pump grinds. Running is not the same as fine.
Myth: a two-stroke additive lets you to drive home. It is an old fix, supposed for another fault. None of what petrol thinned is put back by it — and afterwards, the tank still contains the petrol.
If the motor has been run, part of that petrol is in the filter and the lines, not your tank — and the next start pulls it right back through the pump. So the myth "drain that tank yourself and you are sorted" does not stand up. Also, a can of petrol drained by the kerbside is truly risky.
How petrol ends up: petrol in a diesel
A careless moment is seldom the cause, and no one means to do it. The petrol nozzle is the slimmer of the two and slides into a diesel filler with almost no resistance; a diesel nozzle mostly won't go into a petrol car at all. The forecourt makes it simple, and the slip runs one way.
Routine and your car falling out of step is how it occurs. Hire cars, courtesy cars, and vehicles that are new to you. Two cars on one driveway, one petrol, one diesel. A well-known forecourt with the pumps in a different order. Racing for a train outside Salisbury and fuelling up en route. Years of petrol motors behind you, a diesel Volkswagen Golf in front of you on the forecourt for its first tank — that is when. Your hand repeats what it has always done once you add rain, a phone call or a back seat full of children.
How to prevent petrol in a diesel on your next fill-up in Old Sarum
- Green for unleaded and black for diesel is usual 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 there on your first fill in a motor you do not know.
- Good intentions do less than a sticker or a fob in a vivid colour on your diesel's key if a house has one of each. So mark it.
- It seems daft and it does the trick: on the first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the petrol pump.
- Mistakes like this are simple to make while your mind is on something else, and so your phone goes away.
- Some diesels have a filler designed to refuse a petrol nozzle, and devices you can add are available for motors without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop reading the petrol pump.
- As soon as you realise, stop: less petrol inside the tank makes a weaker mix. What to do next doesn't change, though — still do not fire it up.
Already put petrol in a diesel in Old Sarum?
The order of things is brief, then. Starting it is out, and so is switching on the ignition. If you're still at the forecourt — BP or anywhere else — ask the staff to help you roll the vehicle clear of the petrol pump. Ring 0333 366 0103 next, with three facts — the fuel, the rough quantity, and whether it has run.
If it was AdBlue rather than petrol, say so. That is a separate issue — corrosion and deposits and not lost lubrication — and it has its own page for Old Sarum.
Old Sarum petrol in a diesel jobs: why one costs more than another
The four scenarios above are four different tasks, so no single price for this would be fair. What moves your cost is chiefly which of them you are in. The share matters next, meaning how much of the tank is petrol, followed by the position of your car and whether getting to it is safe for a van.
Before any quote, not after, we ask three queries: the fuel that went in, the volume, and if it's run. That's why. Their answers are what change a range into one firm number.
About Old Sarum itself
Old Sarum is a village in Wiltshire, situated near the city of Salisbury, with a mix of semi-detached housing and other residential properties. Old Sarum sits inland, approximately 77 metres above sea level, and is close to nearby places such as Ford and Hampton Park. Old Sarum is located near the edge of Salisbury, with the city centre just over 2 miles away. Old Sarum has a population of around 1540 people, living in a variety of housing types, predominantly semi-detached homes.
Across Wiltshire and in Old Sarum: fuel drain cover
Ford, Hampton Park and Bishopdown are among the places near Old Sarum that the same vans work, answering petrol in diesel call-outs across Old Sarum's SP postcode area. You need not move your car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all places where we work.
In Old Sarum and still at the pump?
Nothing beats it: that's where you are. Keep it off. Phone.