Petrol in a Diesel Car in Milltown: How Worried Should You Be?
Less than you probably are, provided it hasn't been started. "Have I ruined it?" is the first question anyone in Milltown asks, and the honest answer is generally no, since petrol left in a diesel tank harms nothing until it is dragged through the fuel system — by ignition priming, by the starter, or by driving. Leave your engine off and call Petrol in Diesel — that is how you keep it that way. The remainder of this page explains what petrol actually 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 engine?
Passing through an engine, diesel is doing two things at once. It combusts, and before it burns it lubricates. Designed to extremely fine clearances, the fuel injectors and your pump depend on the diesel flowing through them to keep their surfaces from wearing against one another.
The second job petrol doesn't do at all, and the first it does poorly. Being less viscous than diesel, petrol strips away the protection a fuel system needs, leaving 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 get the rattling.
The shape of the issue is plain when you put those together. Not contact but circulation is what does the damage. Petrol in a tank is a fuel problem. A pump that has been labouring on that petrol is the beginning of a mechanical one, and whatever a worn pump sheds moves on with your fuel to the fuel injectors further on.
How serious is petrol in a diesel? Four situations we see around Milltown
Filled but not once started — as good as it gets. The petrol is inside the tank and only that tank, and the job is a drain and a flush where your car sits. This is the one situation that can only really happen on a forecourt, as anywhere else the car has been driven to get there.
Your ignition switched on, or a short start. With the system primed, the lines and filter already contain petrol that came from that tank. Still usually easy: drain, flush, and the filter dealt with.
Those few miles on the road meant the pump labouring on fuel weakened by petrol throughout. How hard your car was driven counts as much as how far, and this work takes in your tank, your lines, the filter and fresh fuel through the whole circuit. Driving the children to the local primary school is one sort of trip. A run as far as Lisburn, under 3 miles away, is a very different job. So is any distance on the M77, over 50 miles from Milltown, where your engine has been working hard the whole time.
Driven until it complained. Knocking, a lumpy idle, smoke, a throttle that has gone soft. The fuel isn't acting like diesel any more, and your engine is saying so. Pull up on the spot — on the verge on Heugh Road, at the kerb, down a side road — and do not move it again. The fuel drain and flush-through still come first, and they deal with it: if a car is stopped quickly, permanent damage is very rare.
Milltown motorists and the petrol in a diesel myths they hear
Myth: "Fill it the rest of the way with diesel and it will be fine." It will not. Nothing is removed by topping up — you are left with a fuller tank, still the same mixture. That advice assumes a diesel fuel system handles petrol by percentage. It doesn't.
If anything, the reverse holds. Myth: "A modern diesel can cope with a bit of petrol." A modern diesel runs its fuel through smaller components at higher pressure, which makes the lubrication count more, not less.
Myth: "If it starts and drives, there's no damage done." This is the one that catches motorists. Feed diesel to a petrol engine and it normally will not run, so the motorist stops — and the harm stops with them. Nothing looks to have happened when a diesel fed petrol fires up, ticks over and drives away, as it usually will; meanwhile your pump wears. A running engine doesn't mean fine.
Myth: a two-stroke additive makes it safe to drive home. It was an old fix, meant for another problem. It does not put back what petrol has diluted, and that petrol is still in that tank afterwards.
Myth: "Drain the tank yourself and you're sorted." Once your engine has run, some of that petrol is no longer in the tank: it is in the filter and the fuel lines, and it goes straight back through the pump on your next start. Emptying petrol into a can at the kerbside is also genuinely dangerous.
How it happens: petrol in a diesel
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 slips into a diesel filler with almost no resistance, whilst a diesel nozzle mostly won't go into a petrol vehicle at all. So the error runs one way.
When habit and the vehicle stop matching, it occurs. Courtesy car, hire car, or a motor that is brand new. Households running one of each, petrol and diesel. Your normal forecourt, its pumps now in a different order. Fuelling up in a rush on the way to the nearest station, with a train to catch. Precisely the moment it occurs: after years of driving petrol, someone fills a diesel Volkswagen Golf for the first time. Your hand does what it has always done when you add rain, a phone call or a back seat full of kids.
How to avoid petrol in a diesel on your next fill-up in Milltown
- Not every forecourt in the UK keeps to green for unleaded and black for diesel, even if most usually do. Check the petrol pump's label; the colour is just a hint.
- Inspect your filler flap. Many motors state the fuel inside the flap or on the cap. Look at it on your first fill in any motor you do not know.
- 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.
- Say it before you lift it. On your first fill in a new or hired car, say "diesel" aloud before you lift the nozzle off the pump. It seems silly and it works.
- Thinking about something else is when this becomes an easy mistake to make, so tuck the phone away and keep your mind on the pump.
- Add-on devices exist for cars without one, and some diesels are built with a filler that will not take a petrol nozzle. Useful — but a backstop at best, never a reason to stop checking the label.
- Stop as soon as you notice. Less petrol in the tank makes a thinner blend. It doesn't change what to do next, which is still not to fire it up.
Put petrol in a diesel around Milltown already?
The order of things is brief, then. Do not start the vehicle, and don't turn your ignition on. Ask the attendants to help you push it away from the petrol pump if you are still at the forecourt, whether that is the nearest petrol station or anywhere else. Phone 0333 366 0103 next, with three facts — your fuel, the approximate amount, and if it has run.
Corrosion and deposits form the problem with AdBlue, whereas petrol means lost protection. So if it was AdBlue, say so — and read its own Milltown page.
Why one petrol in a diesel job around Milltown costs more than another
There is no fair single price for this, since the four scenarios above are four separate jobs. What shifts the cost is mostly which of them you are in. Two things follow that: the petrol that went in as a share of what that tank holds, then the place your car is in and whether a van can get to it safely.
Before any quote, not after, we ask three questions: your fuel that got in, its volume, and if it's run. That's why. A range becomes a straight figure when the answers are in.
About Milltown itself
Milltown is a locality situated inland in County Antrim, Northern Ireland, with an elevation of 67 metres above sea level. Milltown lies close to the city of Lisburn, approximately 2.1 miles away, and is near other places such as Dunmurry, Ballyskeagh, and Tullynacross. Milltown has a population of around 1633 people and predominantly consists of semi-detached housing. Milltown is located about 322.9 miles northwest of London.
Fuel drain cover in Milltown and across County Antrim
Dunmurry, Ballyskeagh and Tullynacross are among the locations near Milltown that the same teams work, answering petrol in diesel calls across Milltown's BT postcode area. Our technicians drain wherever the vehicle is — your own driveway, a lay-by, a supermarket car park, a forecourt — so it does not have to come to us.
Still at the petrol pump around Milltown?
In that case, you could not be in a better spot. Keep it off. Call.