--- title: Fuel Drain in Underwood — Petrol in a Diesel Car canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/underwood-devon/ location: Underwood county: Devon latitude: 50.385940 longitude: -4.063260 service: Petrol in a Diesel Car updated: 2026-10-28 --- # Underwood: Put Petrol in a Diesel Car? With your tank still carrying the petrol and the motor not yet turned over, nearly every job needs only a drain, so leave the motor off. That outcome is decided in the minutes right after filling up, and not by the amount that went in. Across Underwood and the remainder of Devon, Petrol in Diesel drains the car and cleans it where it stands, whether at a roadside, on a drive or at a forecourt. Contact us before everything else begins, so you'll hear what happens from there. ## What next? Petrol in a diesel, step by step - Give a petrol engine diesel and it will usually fail to run at all, so the person stops there and so does the wear. Feed a diesel petrol and the car starts, it idles, it moves off — fine enough for a couple of miles. Drivers have that muddled, which is the bit they get wrong about petrol in a diesel in particular. So do not crank it. And once started, never depend on it: the fuel system is wearing whenever you drive. - Diesel combusts, and before it combusts it lubricates — your injection pump, the injectors. Petrol does only the burning. So leave the ignition off too: switching it on is commonly all it takes to prime your system, and priming carries petrol from the tank into just those components. - Never tip diesel on top to dilute it. A diesel fuel system doesn't handle petrol by percentage the way that guidance presumes, and topping up clears nothing — it merely gives you a bigger tank of the same blend. The grade makes no difference either: super unleaded is simply petrol. - We'd sooner travel to a tricky spot than have it started — so if you sensibly can, sit tight. Nothing is quicker to sort than a car that has never moved. On the verge on Underlane, that means hazards on and leave it. - Check where you are before phoning. A postcode that starts PL7 1, and the name of whatever is next to you. Otherwise the technician circles instead of turning up. - Three facts shape the entire call-out: the stuff you put in, the approximate amount involved, plus whether anything has been running since. Our line is 0333 366 0103. Don't run it home. Petrol-thinned diesel has gone through that injection pump in real quantity on the road in, and the trip back would close to double that for nothing at all. Phone — the platform is good. There is no need to stand over your Volkswagen Golf at Plymouth while the work happens, and we would much rather talk to you tonight than discover on Monday. ## Forecourt drains for petrol in a diesel A large chunk of this job is completed at a forecourt, since that is where it usually kicks off. If you're still on the forecourt at Texaco, that's typically where the drain takes place — we operate on petrol station forecourts all the time, with the owner's permission. A forecourt is the single location the mistake gets halted before your engine has fired. Anywhere else — a car park, a drive, a lay-by — your car was fired up and driven to get there, which means fuel was drawn from that tank, through your filter and into your high-pressure pump. That's not a calamity, and our engineers can still deal with it where it stands. It does mean the fuel lines and the fuel filter need cleaning as well as that tank, and that is settled by the few seconds between reading the till receipt and reaching for your key. The attendants will normally happily wheel the car out from the pump so the next customer can get through. It is worth doing. Cranking the car over four vehicle lengths? No. Diesel Renault Clio. A couple of litres of unleaded. Driven a couple of miles. Turned off now, at The Co-operative Food. That's the call our technicians hope for, since the real question under it is about amount through the pump instead of hours on the clock. ## Service in Underwood St Stephens Place, Plympton, Colebrook, Woodford, Plympton St Maurice — every one of those on our trips that take us across to Underwood itself, a residential suburb. Not on the list? That means nothing. The places above are simply the nearest few, and nearly all towns across Devon have a page of their own elsewhere on the site. Ring us and enquire rather than presuming, especially if you're on the border or anywhere your satnav gets wrong. The area the page spans sits on our map. Every bit of it is territory our technicians work: a kerbside, a forecourt, a private drive, a car park. You never move the car anywhere. ## Kerbside call-outs in Underwood Not everyone has the opportunity to pull in somewhere sensible. Set off, then noticed? Ended up by the verge on Lavinia Drive, or sat in some lay-by with your hazards flashing? That's a routine call here. Not an unusual one. Clear of the motor when it isn't wise to be there, with it if it is. It will usually oblige. A diesel running on petrol limps along perfectly willingly, and that is the catch: start it up to get to somewhere handier and the blend goes further into your fuel system with every mile driven. However awkward the spot, it's no problem for us to come to it, and that's much better for the vehicle than pressing on. The components that should be getting protected are grinding instead, and your vehicle gives no sign of that: a diesel on a weakened tank starts and pulls away perfectly well. Chance the trip home from The Sir Joshua Reynolds? No. Call us then leave the BMW 3 Series where it is. ## Some miles on petrol in a diesel: what next? The local M5 is the one that matters now, and sits under 50 miles from Underwood. A misfilled diesel will often get you onto it and some distance along before anything seems wrong, while the signs when they arrive are typically lost power, an uneven idle and smoke instead of a tidy stop. Take the first junction that is safe, stop there, and don't restart the vehicle to move it. It alters what our technicians bring, so say so when you phone: on a longer trip — anything close to the under 5 miles to the closest city — take it the petrol has been through your filter, the pump and the fuel injectors. Sitting still, it gets no worse. The pump isn't turning, so whatever occurred on the way to Hardwick Wood in that diesel Nissan Qashqai is finished happening. Time is yours. Just don't take it home on the motor to find more of it. ## Where is Underwood? Underwood is a suburban area in Devon, situated near the coast and approximately 3.6 miles from Plymouth. Underwood has a relatively low elevation of 24 metres and is characterised by semi-detached housing. Underwood is close to other nearby places such as St Stephens Place, Plympton, and Colebrook, and is part of the larger Plymouth urban area. ## What we do when we arrive with you in Underwood - The replies change the work, which is why we ask before giving a price: what went in, how much of that, and whether your engine has run. - The polluted mixture comes from the tank. - Fuel lines are flushed through and your filter cleaned, leaving nothing in your system that caused any of this. - Our technicians pour new diesel in and prime the fuel system. - Our engineers turn it on and confirm it runs smoothly on clean diesel. At that point it is ready to set off. Lasting damage is very rare when it has been spotted early, and because everything is done where the vehicle is, it never needs to go to a workshop. ## AdBlue in your diesel tank by mistake, around Underwood? AdBlue instead of petrol? Then the first instruction is unchanged — your engine remains off — whereas the issue beneath it's a separate one altogether. Thinned diesel, and no lubrication left for your fuel system that depends on it. That is petrol. Rust and residue are what a diesel tank gets instead, because AdBlue is urea in water. Both are ours. There is a separate Underwood page for AdBlue removal, with the detail on it — including the reasons it usually turns out to be the worse of the two. ## How much is a petrol-in-diesel drain around Underwood? One figure wouldn't be honest here, as this isn't one job. These are the things that shift it: - This is the big one: whether the motor has been started, or driven. - How much of the wrong fuel was put in, set against how much that tank takes. - The sort of liquid in the tank, petrol or AdBlue. - Whether our van can sensibly get to the car and work on it, which hinges on where your vehicle is. The vehicle, the amount, whether it has run — give us those and the answer comes back straight rather than as a range. Motor at home, going nowhere, nothing urgent about it — is fine for that. What happens next is the trouble. Your engine immediately pulls the petrol left resting in your filter and the feed lines back round through your pump a second time, since emptying a tank does nothing about fuel that has already left it. Drain it then put fresh diesel in, a person certain will tell you — and that tip is half true, since do it to a diesel Vauxhall Insignia parked up, Living Well Church say, and the thing starts, which is what makes it sound sensible. Phone us instead. We flush the system and take the fuel filter off where your vehicle has a workable one, and that's the difference between the car being fixed and your car merely starting. ## Petrol in diesel queries from Underwood motorists ## I am on a forecourt in Underwood. Can you drain the vehicle on the spot? Yes, and it is where a large portion of this work gets done. Agreement from the site is the condition. Given that, a forecourt like Sainsbury's is somewhere we're frequently, along with the rest of them locally — so name yours on the phone and you'll hear if working there's possible. ## Is there a safe quantity of petrol in a diesel? Whether your motor has run matters a lot more, though the proportion counts too, rather than the litres. A nearly empty tank with five litres in it, against a full one with the same five: distinct situations, certainly. Either way, the work needed comes down to one thing, which is whether your fuel system has had that mixture drawn through it. ## Already driven it with petrol in the diesel? Now what? Stop sensibly. Off. Nothing after that. It is fixable much more frequently than people assume, even though driving is what moves the issue from your tank into your pump and injectors — and the single most useful thing you can do now isn't restart it. ## Is a fuel drain going to void my warranty? A drain and flush carried out correctly is not a change and does not invalidate a manufacturer's warranty. A dispute over a warranty is likelier to come from running a diesel on petrol — so leave it switched off. ## Adding two-stroke oil, then driving home Two-stroke oil solves a different issue, and an old one at that. Nothing it does puts back what petrol thinned. No. Afterwards? Still petrol in that tank, and a pump that has to cope with the stuff. ## Main dealers and petrol in a diesel There's no need to bring it to a franchised dealer, because our engineers drain and flush your car wherever it is. ## Still with your car? Leave it shut off. Driven it already? Then somewhere safe, stop, turn off, and no restarting the car later on. A still, cold motor is the best place to be in, and this is recoverable from far more regularly than drivers fear. Emptying wrongly fuelled cars, Underwood and the rest of Devon, wherever they are. Roadside. Forecourt. Home.