How Worried Should You Be? Petrol in a Diesel Car in Frank Hill
Probably less than you already are — provided no one has started it. Everyone in Frank Hill starts with "have I wrecked it?", and the honest answer is generally no: petrol left in that tank of a diesel stays harmless till priming, cranking or driving draws it into the system. Keep it like that: leave your engine off and ring Petrol in Diesel. The remainder of this page covers what petrol really does to a diesel, how to judge how far it has got, and how to make sure it doesn't happen to you a second time.
Petrol in a diesel: what does it do to the motor?
Two jobs fall to diesel on its route round a motor. It lubricates first, and only then does it burn. Your high-pressure pump and the fuel injectors are made to very fine gaps, and your diesel passing through them is what stops those surfaces from wearing against one another.
The second job petrol doesn't do at all, and the first it does badly. Being less viscous than diesel, petrol strips away the lubrication a fuel system needs, leaving a pump on the mixture wearing itself. It's equally made to resist igniting under compression — the reverse of what a diesel needs — which is why you get the clattering.
Put these together and the shape of the trouble is clear. Not contact but movement is what does the harm. All a tank with petrol in it amounts to is a fuel problem. The start of a mechanical one is a pump that has been labouring on that petrol — and whatever a worn pump sheds travels on with the fuel to the fuel injectors downstream.
Four scenarios our engineers see around Frank Hill: how bad is petrol in a diesel?
Fuelled but not once started — the best it gets. On a forecourt, and really only there, that petrol is still limited to that tank — since anywhere else the car was driven to get to it. The job is emptying and flushing on the spot.
A brief spell of running, or just your ignition on. Petrol has left your tank and got to the filter and the fuel lines, since your system has been primed. Drain, flush, deal with the filter: still normally simple.
Those few miles driven were the pump working on fuel diluted by petrol throughout. Tank, lines, filter, then fresh fuel run through the entire circuit: that is the work, and the way the car was driven counts as much as the miles. Driving the children to Northmoor Academy is one sort of trip. Very different a second time: a run to Manchester, under 10 miles away, or some miles on the Broadway, under 3 miles from Frank Hill, where the motor never stopped labouring hard.
It complained, and only then stopped: smoke, clattering, a throttle gone soft, an idle gone ragged. What you are hearing is the engine reporting fuel that no longer behaves like diesel. Leave it where it has stopped: a lay-by, a quiet street, the verge on St Mary's Way. A vehicle pulled over quickly very seldom has lasting damage, as the fuel drain and the flush, which still come first, take care of it.
Frank Hill drivers and the petrol in a diesel myths they hear
False: topping up to full with diesel makes it fine. It does not. A fuller tank of the same mix is all you get, since topping up removes nothing. 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." Protection counts more on newer diesels, not less, since their fuel runs through finer parts at higher pressure.
This is the one that catches people. Myth: "If it starts and drives, there's no harm done." Diesel in a petrol motor generally means a motor that will not run: the motorist stops, and so does the harm. While the pump wears, a diesel fed petrol normally starts, ticks over and drives away as if nothing has happened. Fine and running aren't the same at all.
An old fix for a distinct fault lies behind this one. Myth: "Add some two-stroke oil and drive the vehicle home." That petrol is still inside that tank after that, and what it has diluted isn't put back.
Myth: "Drain that tank yourself and you're sorted." After the engine has run, some of that petrol is no longer in your tank: it is in your filter and the fuel lines, and it goes straight back through the pump on the next start. It's also genuinely hazardous to drain petrol into a can by the kerbside.
Petrol in a diesel: how does it take place?
A careless moment is seldom the cause, and no one means to do it. The forecourt makes it easy: the petrol nozzle is the smaller of the two, and it slides into a diesel filler with almost no resistance, while a diesel nozzle generally will not go into a petrol vehicle at all. So the error runs one way.
When habit and the vehicle stop matching, it occurs. Hire cars, courtesy cars, and cars that are new to you. One petrol and one diesel on the driveway of the same household. A forecourt you know, only with its pumps laid out differently. Filling up in a rush en route to Mills Hill, with a train to catch. Years of petrol vehicles behind you, a diesel Volkswagen Passat in front of you on the forecourt for its first tank — that's when. Add rain, a phone call or a back seat full of children, and your hand repeats what it has always done.
Frank Hill motorists: how to prevent petrol in a diesel next time
- Read the petrol pump, not the colour. In the UK unleaded handles are usually green and diesel black, but not on each forecourt. The label is what matters.
- Inspect your filler flap. Many motors state the fuel type inside the flap or on the cap. Look at it on the first fill in any vehicle you do not know.
- Good intentions do less than a sticker or a fob in a vivid colour on your diesel's key when a house has one of each. So label it.
- Say it before you lift it. On the first fill in a new or hired car, say "diesel" out loud before you take the nozzle off the pump. It seems daft and it does the trick.
- Put your phone away. This is an easy mistake to make whilst you are thinking about something else.
- Add-on devices exist for cars without one, and some diesels are built with a filler that won't accept a petrol nozzle. Helpful — but a backstop only, never a reason to stop checking the label.
- Less petrol means a weaker blend, and so stop as soon as you notice — while remembering that your next step is unchanged. It is still not to fire it up.
Petrol already in a diesel around Frank Hill? Begin here
Then the order of things is short. Starting it is out, and so is switching on your ignition. If you're still on the forecourt — Sainsbury's or anywhere else — ask the staff to help you push it clear of the pump. Next, 0333 366 0103. We will ask what went in, about how much, and if it has been run.
If it was AdBlue instead of petrol, say so. That is a separate issue — corrosion and deposits instead of lost lubrication — and it has its own page for Frank Hill.
What makes one Frank Hill petrol in a diesel task cost more than the next
A fair single price does not exist here: four scenarios, four separate jobs. What moves your cost is chiefly which of them you're in. The share counts next, meaning how much of that tank is petrol, followed by the location of the car and whether getting to it is safe for our van.
What was put in, how much, and whether it has run — three questions our engineers ask before quoting, not after, for precisely that reason. Those answers are what turn a range into one firm number.
About Frank Hill, briefly
Frank Hill is a suburban area in Greater Manchester, situated approximately 6.9 miles from Manchester city centre. Frank Hill occupies higher ground at around 215 metres, overlooking the surrounding urban landscape. Frank Hill is characterized by a high proportion of flat dwellings, which dominate the local housing stock. Frank Hill is close to nearby towns such as Oldham and is part of the larger Manchester urban area.
Frank Hill and Greater Manchester: where our fuel drain cover reaches
Frank Hill waits in the OL postcode area, and our teams that answer petrol in diesel calls there work the spots near it as well — Oldham, Cold Hurst Hollow and Cold Hurst among them. The vehicle doesn't need to move to us: our engineers drain on a forecourt, in a supermarket car park, in a lay-by or on your own drive.
Frank Hill: still at the petrol pump?
No position is better: that's where you are. Keep it off. Ring.