Dyke House: Petrol in a Diesel Car? How Worried to Be
Not started? Then less worried than you likely feel. Everyone in Dyke House begins with "have I ruined it?", and the fair answer is generally no: petrol resting inside the tank of any diesel remains harmless until priming, cranking or driving draws it into the system. Petrol in Diesel is who to ring, with the motor left off, and so it remains that way. Keep reading for three things: the effect petrol has inside a diesel motor, the clues of how far it has spread, and the way to make sure you don't do it again.
Your engine and petrol in a diesel: what happens
Diesel has two jobs on its way through an engine. Before it combusts, it lubricates — then it ignites. Your high-pressure pump and the fuel injectors are designed to extremely fine tolerances, and the diesel passing through them is what keeps those surfaces from wearing down against one another.
Of those two tasks, petrol manages the first poorly and the second never. Being less viscous than diesel, petrol strips out the lubrication a fuel system needs, so a pump running on the blend wearing itself. It is also made to resist igniting under compression — the reverse of what a diesel needs — which is where you hear the rattling.
The shape of the trouble is clear once you put those together. Contact doesn't do the harm — circulation does. All a tank with petrol in it amounts to is a fuel problem. Whatever a worn pump sheds goes on, carried by the fuel, into your injectors downstream, which is why a pump that has been working on that petrol is where a mechanical problem starts.
Four scenarios we see in Dyke House: how bad is petrol in a diesel?
Filled up, never started. The best case there is. That petrol is inside your tank and just your tank, and the job is a drain and a flush where the car sits. This is the one situation that can only really occur at a forecourt, as anywhere else the car has been driven to get there.
Ignition on, or started for a moment. Petrol has come out of your tank and reached the fuel filter and your lines, because your system has been bled. Usually nothing more than draining, purging and seeing to your filter, so still straightforward.
Driven a couple of miles. Now the pump has spent those miles labouring on thinned fuel. Miles is only half of it; how hard it was driven matters just as much. Either way the work includes the tank, your lines, the filter and fresh fuel through the entire system. On the school run to Brougham Primary School, the mileage is small. Any distance on the A1(M), under 15 miles from Dyke House, means the motor working hard throughout, and a run to Sunderland, under 25 miles away, is a very different task too.
Knocking, a lumpy idle, smoke, a throttle gone soft: driven till it complained. That's your motor telling you its fuel no longer is behaving like diesel. Stop wherever you are — the verge on Amberton Road, a lay-by, a side street — and leave the car where it is. The fuel drain and flush-through still go first, and they take care of it: if a car is stopped soon, lasting damage is very uncommon.
Myths Dyke House drivers hear about petrol in a diesel
"Top it up the rest of the way with diesel and it will be fine" — a myth. It will not. Nothing is removed when you top up — that tank simply carries more of the same blend. That guidance supposes a diesel fuel system tolerates petrol by percentage. It doesn't.
If anything, the reverse is true. Myth: "A current diesel can cope with a bit of petrol." Smaller parts and higher pressure are how a newer diesel runs its fuel, and that makes the lubrication count more, not less.
Myth: "If it starts and drives, there's no damage done." This is the one that catches drivers. Feed diesel to a petrol engine and it usually will not 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. A running engine doesn't mean fine.
Myth: "Add some two-stroke oil and drive the vehicle home." It's an outdated workaround for a different issue. The petrol is still inside that tank afterwards, and whatever it has thinned isn't put back.
"Drain it yourself and you're sorted" — a myth, since after it's been running some petrol sits in the filter and lines, waiting to go right back through the pump on your next start. Also, a can of petrol drained at the roadside is truly hazardous.
How does petrol in a diesel happen?
On purpose? Never. Through carelessness? Rarely, if ever. A diesel nozzle generally will not go into a petrol motor, yet the slimmer petrol nozzle goes into the filler of a diesel almost without resistance — so forecourts make this one error simple, and just in that direction.
The moment routine stops matching the vehicle is the moment it happens. A new motor, a hire car or a courtesy car. A household with one petrol and one diesel on the driveway. A well-known forecourt with the pumps in a different order. A rushed fill on the way to Hartlepool with a train to catch. Years of petrol cars behind you, a diesel Volkswagen Golf in front of you on the forecourt for its first tank — that is when. With rain, a call coming in, or children to deal with, your hand just does what it always has.
How to prevent petrol in a diesel at your next fill-up in Dyke House
- Check the pump, not the colour. In the UK unleaded handles are usually green and diesel black, yet not on each forecourt. The label is what counts.
- The first fill in an unfamiliar car is the time to check the filler flap — inside it, or on the cap, many cars state which fuel they take.
- Good intentions do less than a sticker or a fob in a vivid colour on the diesel's key when a house has one of each. So mark it.
- It seems silly and it works: on your first fill in a new or hired car, say "diesel" out loud before you lift the nozzle off the petrol pump.
- Tuck the phone away. This is an easy mistake to make whilst you are thinking about something else.
- Up to a point, a misfuel inhibitor helps: some diesels come with a filler designed to refuse a petrol nozzle, and aftermarket devices are available for the rest. Count it as a backstop, then keep reading the pump.
- Less petrol makes a weaker mix, and so stop as soon as you realise — while remembering that your next stage is unchanged. It is still not to fire it up.
Dyke House: already put petrol in a diesel?
Then, there is only a short order of things. Starting it is out, and so is turning on the ignition. The attendants at the forecourt — whether at Asda itself or wherever you filled up — will normally help roll it clear of the pump if you ask. Next, 0333 366 0103. We will ask what went in, about how much, and if it's been run.
AdBlue, not petrol? Then say so. Corrosion and deposits, not lost protection, make it a different fault — Dyke House has a page just for it.
Dyke House petrol in a diesel jobs: why one costs more than another
There's no honest single price for this, since the four scenarios above are four separate tasks. Mostly, your cost moves with which situation you are in. Two things come after that: the petrol that got in as a share of what the tank takes, then the place the vehicle is in and whether a technician can reach it safely.
That's why our engineers ask three questions before quoting instead of after: what was put in, how much, and if it has run. A range becomes a straight figure once those answers are in.
About Dyke House and its setting
Dyke House is a suburban area located on the coast of County Durham, with an elevation of approximately 7 metres above sea level. Dyke House sits near the towns of Middleton and Hartlepool, and is within commuting distance of Sunderland, which is around 15.7 miles away. Dyke House is characterised by its predominantly semi-detached housing stock, which reflects the typical residential development of the region. Dyke House is situated in a part of the country with a rich industrial heritage, near the mouth of the Tees estuary.
Across Durham and in Dyke House: fuel drain cover
Dyke House rests in the TS postcode area, and our teams that answer petrol in diesel calls there work the spots around it as well — Middleton, Hartlepool and Throston among them. A forecourt, a supermarket car park, a lay-by or your own driveway are all locations we drain, and the car doesn't need to move to us.
Dyke House: still at the petrol pump?
The best place there is, then — that is where you are. Turned off it remains; then call.