Tregolls: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less worried than you probably feel. Till the ignition primes your pump, the starter turns, or the car is driven, petrol in a diesel tank simply sits there and does no harm. Which means the truthful reply to the first Tregolls question — "have I ruined it?" — normally no. Leave your engine off then phone Petrol in Diesel — that keeps it that way. What petrol actually does to a diesel, how to judge how far it's travelled, and how to stop it from happening again: that is the remainder of this page.
The motor and petrol in a diesel: what happens
Two jobs fall to diesel on its journey through a motor. It lubricates first, and only then does it burn. Designed to very fine gaps, the fuel injectors and the pump rely on the diesel flowing through them to keep their surfaces from wearing against one another.
Of those two jobs, petrol manages the first poorly and the second never. It's thinner than diesel and takes away the lubrication the system hinges on, and so a pump running on a petrol mixture is a pump wearing itself. And petrol is made to resist igniting under compression, which is the opposite of what a diesel needs from its fuel. That is where the knocking comes from.
Put these together and the shape of the trouble is clear. It's circulation that does the damage, not contact. All a tank with petrol in it amounts to is a fuel issue. Whatever a worn pump sheds goes on, carried by the fuel, into the fuel injectors downstream, which is why a pump that has worked on the petrol is where a mechanical problem starts.
Four scenarios our technicians see in Tregolls: how serious is petrol in a diesel?
Fuelled up, not once started. The best case there can be. Being on a forecourt is what makes this the case: elsewhere, the vehicle has been driven there to begin with. With that petrol kept inside your tank alone, it's drained and flushed on the spot, and nothing more is needed.
Ignition on, or started for a moment. Once primed, your system has pulled petrol out of the tank up to the fuel filter and the lines. Still usually simple: drain, flush, and your filter dealt with.
Those few miles on the road were the pump working on fuel thinned by petrol throughout. Distance is only half of that; how hard it was driven counts equally. Either way this work includes that tank, the lines, the filter and clean fuel through the whole circuit. Driving the children to Stithians Community Primary School is one kind of trip. Driving as far as Truro, under 10 miles away, makes a very different task — as does any mileage on the M5, over 50 miles from Tregolls, with your engine working hard all the way.
Driven on until it protested — rattling, smoke, a ragged idle, a dead throttle. That is your engine telling you its fuel has stopped behaving like diesel. Leave it wherever it has stopped: a lay-by, a quiet street, the verge on South Road. Permanent damage is very uncommon when a vehicle is pulled over early, and the fuel drain and flush-through that still go first deal with it.
Tregolls motorists and the petrol in a diesel myths they hear
It will not be fine. The myth: "Fill it the rest of the way with diesel and it will be." Nothing is removed by topping up — you are left with a fuller tank, still the same mixture. A diesel fuel system doesn't accept petrol by percentage in the way that guidance presumes.
Myth: "A modern diesel can cope with a bit of petrol." If anything, the opposite. Lubrication matters more on newer diesels, not less, because their fuel passes through finer parts at higher pressure.
One myth that catches motorists off guard: if it starts and drives, it must be unharmed. Feed diesel to a petrol motor and it normally won't run, and so the motorist stops — and the harm stops with them. Nothing seems to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually does; meanwhile your pump wears. Being able to run is not proof of being fine.
Myth: "Add some two-stroke oil and drive the vehicle home." It is an outdated workaround for a separate issue. None of what petrol diluted gets put back by it — and later, your tank still contains the petrol.
The next start sends petrol back round the pump from the fuel lines and the filter, where some of it ends up once the motor has run. That's why a DIY tank drain does not sort it — a myth. And, a can of petrol drained by the roadside is truly risky.
Petrol in a diesel: how does it occur?
On purpose? Never. Through carelessness? Rarely, if ever. A diesel nozzle mostly will not go into a petrol car, yet the narrower petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error easy, and only in one direction.
It occurs when habit and the vehicle stop matching. Hire cars, courtesy cars, and motors that are new to you. Two vehicles on one drive, one petrol, one diesel. A well-known forecourt with the pumps in a different order. Fuelling up in a rush on the way to Penryn, with a train to catch. Precisely the moment it happens: after years of driving petrol, someone fills a diesel Renault Megane for the first time. Add a back seat full of kids, a phone call or rain, and habit wins.
Next time you fill up around Tregolls: preventing petrol in a diesel
- Read the pump, not the colour. In the UK unleaded handles are generally green and diesel black, but not on every forecourt. The label is what counts.
- The first fill in a strange motor is the time to check your filler flap — on it, or on the cap, many motors state which fuel they take.
- Good intentions count for less than a sticker or a fob in a vivid colour on your diesel's key when a house has one of each. So mark it.
- It seems daft and it works: on the first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the pump.
- Whilst you are thinking about something else, this is an easy mistake to make — so tuck the phone away.
- Some diesels come with a filler built to block a petrol nozzle, and devices you can add exist for vehicles without one. Such an inhibitor helps up to a point — as a safety net, not a reason to stop checking the pump.
- Less petrol means a weaker mixture, and so stop the moment you notice — though remembering that the next stage is unchanged. It's still not to start the car.
Already put petrol in a diesel in Tregolls?
Short and simple, then, is the order of things. Never crank it, and do not switch the ignition on. The attendants at the forecourt — whether at Gulf itself or wherever you filled up — will normally help push it away from the pump if you ask. What went in, about how much, and if it's run: tell us that when you phone 0333 366 0103.
Say so if it was AdBlue instead of petrol: it is a different problem, with its own page for Tregolls, because AdBlue brings corrosion and deposits instead of lost lubrication.
One petrol in a diesel task around Tregolls costs more than another. Why?
The four scenarios above are four different jobs, so no single price for this would be fair. The scenario itself does most of the work of moving the cost. Two things come after that: the petrol that got in as a proportion of what that tank holds, then the place the car is in and whether a technician can get to it safely.
What got in, how much, and whether it's run — three questions we ask before pricing, not after, for exactly that reason. A range turns into a straight figure when those replies are in.
About Tregolls and its setting
Tregolls is a locality situated on the banks of a river in Cornwall, with a relatively small population of around 1225 residents. Tregolls is characterized by its detached housing and rural setting, lying approximately 115 metres above sea level. Tregolls is close to the city of Truro, which is about 7.7 miles away, and is also near other places such as Stithians and Hendra. Tregolls is located in the South West region of England, about 238.3 miles from London.
Fuel drain cover across Cornwall, Tregolls included
Our teams answering petrol in diesel jobs around Tregolls, in the TR postcode area, also work the spots near it, Stithians, Hendra and Seaureaugh Moor among them. A forecourt, a supermarket car park, a lay-by or your own drive are all places our technicians drain, and the vehicle doesn't need to move to us.
Still at the petrol pump around Tregolls?
The best position there is, then — that is where you are. Keep it off. Call.