Carnglas: Petrol in a Diesel Car? How Worried to Be
Unstarted? Then less worried than you probably are. Everyone in Carnglas starts with "have I wrecked it?", and the fair answer is generally no: petrol left in the tank of a diesel stays harmless till priming, cranking or driving draws it into the system. Leave your engine off and call Petrol in Diesel — that is how you keep it like that. Keep reading for three things: the effect petrol has inside a diesel engine, the clues of how far it has spread, and ways to make sure you don't repeat it.
Petrol in a diesel: what does it do to the engine?
Passing through an engine, diesel is doing two things at the same time. It burns, and before it burns it lubricates. What keeps the surfaces inside the high-pressure fuel pump and your injectors from grinding against each other is the diesel flowing through them — they're designed to very fine tolerances.
Petrol does the first job poorly and the second not at all. The rattling 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 thinner than diesel, it strips away the lubrication the system depends on, and any pump running on such a mix is wearing itself.
Together, those leave the shape of the trouble plain. The harm is done by movement, not by contact. All a tank with petrol in it amounts to is a fuel problem. The beginning of a mechanical problem is a pump that has been running on that petrol — and whatever a worn pump sheds moves on with your fuel to the fuel injectors beyond it.
Four situations we see around Carnglas: how bad is petrol in a diesel?
Filled but not once started — as good as it gets. At a forecourt, and really only there, that petrol is still confined to that tank — since anywhere else the car was driven to reach it. The job is draining and rinsing on the spot.
The ignition turned on, or a short start. Once primed, the fuel system has pulled petrol out of your tank as far as the fuel filter and the lines. Still normally simple: drain, flush, and your filter seen to.
Driven a few miles. Now your pump has spent these miles working on thinned fuel. How hard your car was driven counts as much as how far, and this work covers that tank, the lines, your filter and clean fuel through the entire circuit. Short trips, like the school run to the local primary school, are one matter. Very different again: a run to Swansea, under 3 miles away, or any distance on the M4, under 5 miles from Carnglas, where your engine kept running hard.
Driven on until it protested — rattling, smoke, a lumpy idle, a dead throttle. What you are hearing is your engine reporting fuel that no longer runs like diesel. Whether it's the verge on LLwyn Mawr Close, a lay-by or a side road, stop there and leave it. A car stopped soon very rarely has permanent damage, since the fuel drain and the flush-through, which still go first, deal with it.
Petrol in a diesel stories Carnglas people 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 bigger tank, still the same mixture. Percentage isn't how a diesel fuel system tolerates petrol, however much that advice presumes.
If anything, the reverse holds. Myth: "A newer diesel can cope with a bit of petrol." A current diesel runs its fuel through finer components at higher pressure, which makes the lubrication matter more, not less.
"It starts, it drives, so no harm done" — the myth that trips up most motorists than any other. Diesel in a petrol motor normally means a motor that won't run: the driver stops, and so does the damage. Feed petrol to a diesel and it usually fires up, ticks over and pulls away like nothing has happened — all the while its pump is wearing. Being able to run isn't the same as being fine.
An old workaround for a different issue lies behind this one. Myth: "Add some two-stroke oil and drive it home." None of what petrol weakened is put back by it — and later, the tank still holds that petrol.
Once the motor has been run, part of that petrol sits in the filter and the lines, not that tank — and your next start sends it straight back through your pump. So the myth "drain that tank yourself and you're sorted" does not hold. It is also truly hazardous to drain petrol into a can at the kerbside.
How does petrol in a diesel take place?
A careless moment is seldom the cause, and nobody means to do it. The petrol nozzle is the smaller of the two and slides into a diesel filler with almost no resistance; a diesel nozzle generally will not go into a petrol car at all. The forecourt makes it easy, and the slip runs one way.
Routine and your car getting out of step is how it happens. Courtesy car, hire car, or a vehicle that is brand new. One petrol and one diesel on the driveway of the same household. A forecourt you know, only with its pumps arranged differently. A train to catch, and a hurried fill en route to Swansea. The first fill-up in a diesel Volkswagen Passat after years of driving petrol is exactly the moment it occurs. Add rain, a phone call or a back seat full of children, and your hand repeats what it has always done.
Next time you fill up around Carnglas: avoiding petrol in a diesel
- Check the pump, not the colour. In the UK unleaded handles are usually green and diesel black, but not on every forecourt. The label is what counts.
- Check the filler flap. Many cars state the fuel inside the flap or on the cap. Look at it on your first fill in any vehicle you don't know.
- Good intentions count for less than a sticker or a fob in a bright colour on the diesel's key when a household has one of each. So label it.
- "Diesel", out loud, before you lift the nozzle — every time a new or hired car needs its first tank. It sounds daft. It does the trick.
- Tuck your phone away. This is an easy mistake to make whilst you're thinking about something else.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler designed to reject a petrol nozzle, and aftermarket devices are available for the rest. Count it as a safety net, and keep reading the petrol pump.
- As soon as you realise, stop: less petrol inside that tank makes a thinner mix. What to do next doesn't change, though — still do not start it.
Petrol already in a diesel around Carnglas? Start here
In that case, there's only a short order of things. Don't crank it, and do not turn the ignition on. The staff at the forecourt — whether at Texaco itself or wherever you filled up — will usually help push it clear of the petrol pump if you ask. What got in, about how much, and if it's run: tell us that when you phone 0333 366 0103.
If it was AdBlue rather than petrol, say so. That's a different problem — corrosion and deposits rather than lost lubrication — and it has its own page for Carnglas.
What makes one Carnglas petrol in a diesel task cost more than the next
The four scenarios above are four different tasks, so no single quote for this would be fair. Chiefly, your cost moves with which one you are in. The share matters next, meaning how much of that tank is petrol, followed by the position of the car and whether reaching it is safe for a technician.
Three questions come first, before any quote, rather than after — what went in, how much, has it run — and that is the reason. The answers turn a range into a straight figure.
About Carnglas itself
Carnglas is a suburban area located on the outskirts of Swansea, situated near the coast in southern Wales. Carnglas sits at an elevation of 127 metres, overlooking the surrounding landscape. Carnglas is characterised by its predominantly detached housing stock, with nearby neighbourhoods including Ty-coch, Penyrheol, and Olchfa. Carnglas is close to the city of Swansea, being only 2.4 miles away from the city centre.
Carnglas and Swansea: where our fuel drain cover reaches
Carnglas rests in the SA postcode area, and the vans that answer petrol in diesel calls there work the locations around it as well — Ty-coch, Penyrheol and Olchfa among them. No need to move the car to us. Forecourts, supermarket car parks, lay-bys and your own drive are all locations we drain.
Still at the pump in Carnglas?
The best place there is, then — that is where you are. Leave the vehicle switched off, then ring.