--- title: Petrol in a Diesel Car Knowle — Fuel Drain canonical: https://www.petrolinadieselcar.co.uk/petrol-in-diesel/knowle-devon/ location: Knowle county: Devon latitude: 50.636460 longitude: -3.342480 service: Petrol in a Diesel Car updated: 2026-10-22 --- # Knowle: Put Petrol in a Diesel Car? If you have not fired up the engine as yet, do not. A fuel drain and nothing more is almost always what a vehicle requires while the petrol is still inside the tank and the motor has not run, which is why it's the next few minutes that matter, not how much went in. Petrol in Diesel goes to your car wherever it has come to rest in Knowle or the remainder of Devon, on the forecourt, at the roadside or on a drive, and drains and flushes it there. Our team shall show you what the following part is. Ring us — that goes ahead of anything else. ## What now? Petrol in a diesel, in turn - As you drive, the pump and your injectors suffer. That is why you don't start the vehicle, and why you do not believe it once it has started. The trick about petrol in a diesel in particular — the part drivers get wrong — is that it drives off happily for the first mile or two. Diesel in a petrol motor generally can't run at all, which stops the driver and stops the wear with them. This one lets you keep going. - Diesel ignites, and before it combusts it lubricates — that injection pump, the injectors. Petrol manages only the burning. So leave the ignition alone too: switching it on is commonly all it takes to prime that system, and priming carries petrol from your tank into just those parts. - Don't weaken it. Diesel added on top takes out nothing, so all you have is more of what was already there, since percentage is not how a diesel fuel system tolerates petrol. Super unleaded? Just petrol. The type makes no difference. - Wait where you are if you sensibly can. A car that has not moved is the quickest one to handle, and we'd sooner come to an awkward spot than have it started. If you're pulled up on the verge on Knowle Road, put the hazards on and keep it there. - Have your whereabouts prepared before you phone. A postcode that starts EX9 6 and whatever is nearest to you with a label on it is the difference between a van showing up and our van circling. - Ring 0333 366 0103. Expect three points — what got in, approximately how many litres, plus whether the car has been run. The replies shape whatever happens next. ## On the forecourt: removing petrol from a diesel It starts at the pump, generally. Often enough the work ends on site too. If you're still on the forecourt at Pace, that's usually where the drain happens — our technicians work on garage forecourts routinely, with the site's consent. Before your motor has fired — the forecourt is the one place it gets halted. Our technicians can still sort it out where it sits, even away from the forecourt. In a car park, on a driveway or in a lay-by, the vehicle has been switched on and driven there, and that drew fuel through the filter and into the high-pressure fuel pump, all the way from the tank. None of that is a calamity, though the flush then has to go past the tank to your lines and the fuel filter, and the few seconds between reading your receipt and going for the keys are what decide that. The staff will generally happily push the vehicle out from the pump so the next customer can get through. That's worth doing. Four vehicle lengths isn't worth a restart. We are in car parks like the one outside The Co-operative Food all the time, and it is almost never the fuel that complicates them. It's that bay. Vehicles both sides. Trolleys stacked up behind. Sometimes a height limit at the way in, which determines whether a technician gets to you at all. So tell us how boxed in you are when you phone, and which way the vehicle is pointing. If there is no clearance to work next to your BMW 3 Series, our technicians shift it without your engine. That isn't pedantry over a handful of seconds: starts prime things, mixture comes out of that tank toward the pump, and a motor moved twice for a nicer bay is gradually a harder job than one nobody touched. ## Coverage near Knowle As a coastal village, Knowle has a regular call, while the places close by go with it on the same trip: Budleigh Salterton and Little Knowle, Kersbrook and East Budleigh, Littleham. Our engineers still come. The places above are just the closest neighbours, and a page exists for the majority of places in Devon, so an absence from the list is not an absence from our coverage. Call us and check rather than guessing — borders especially, and anywhere your satnav tends to struggle with. The ground the page includes is on our map. Kerbside, forecourt, driveway, car park: every bit of it is territory we serve, and none of it asks the car to travel to us. Your diesel Peugeot 308 will have felt perfectly ordinary on the way back from St Peter's Church of England Primary School. They do, and that's the catch with petrol in a diesel instead of the other way round. Put diesel in a petrol vehicle and it mostly won't run, and so the driver stops and the damage stops with them. Put petrol in a diesel and it fires up, idles and pulls away as though nothing has happened — meanwhile the high-pressure fuel pump does its work without the protection the fuel is meant to be providing. Nothing warns you, since from behind the wheel there's nothing to caution you about. Ring us with approximately how far you travelled and how hard you drove it; the second answer matters more than the first. ## Roadside call-outs across Knowle Not everybody gets the chance to pull in anywhere suitable. Hazards flashing in a lay-by somewhere, or pulled onto the verge on Dalditch Lane because you worked it out after setting off — our technicians take that call so often that it is the ordinary kind. Out of your car while it is not sensible to sit there, beside it if it is. Every mile a diesel obliges you for on petrol pulls the mixture further into your fuel system — and oblige it often will, which is why your engine does not get restarted to limp somewhere safer. We'll bring our van to a difficult place without any fuss, and for the vehicle that is much better than driving on. ## Driven it already? Pull in, then see below Here is where your M5 comes in, under 10 miles out of Knowle. A misfilled diesel will frequently get you onto it and some way along before anything feels wrong, while the signs when they appear are normally a drop in power, a lumpy idle and smoke instead of a clean stop. The first safe exit is the one to take. Turn off there, and leave the restarting alone. On a longer run — anything approaching the under 15 miles to the closest city — take it the mixture has been through the filter, your pump and your injectors, and tell us when you ring. It alters what our engineers bring. Normal on the way out, sluggish on the way back. If that's how that trip to Leeford Plantations went, your tank is the place to look. Petrol dilutes diesel, and thinner fuel slips past the tightly fitted parts that are meant to build injection pressure — so the further your Dacia Duster went, the less well it held that pressure. Stop somewhere sensible, switch off then call us. ## All about Knowle Knowle is a small coastal village in Devon, situated near the towns of Budleigh Salterton and Exeter. Knowle sits at a low elevation of around 38 metres, close to the sea and surrounded by other nearby places like Little Knowle and Kersbrook. Knowle has a population of approximately 514 people, living in predominantly semi-detached housing. Knowle is located about 10 miles from Exeter, the nearest city, and around 152 miles from London. ## The job around Knowle, step by step - The responses alter the work, which is why we ask before pricing: what went in, how much of that, and whether your engine has run. - Out goes the tainted fuel. - Our technicians rinse the lines and clear the fuel filter, so what's left in your system isn't what caused the trouble. - Our engineers pour new diesel in and prime the fuel system. - When it is turned on, we make sure it runs correctly on clean diesel. From that point, you are ready to set off. Lasting damage is very unusual when it has been spotted soon, and since all of this is done where the vehicle is, it never needs to be taken to a garage. ## A separate matter: AdBlue in a diesel tank in Knowle AdBlue rather than petrol? Then the first step is unchanged — the engine remains off — whereas this problem underneath it is a separate one altogether. Petrol does two things to diesel: dilutes it, and takes away the lubrication the system depends on. AdBlue is urea in water, and in a diesel tank it leads to corrosion and deposits instead. Our technicians handle both, and AdBlue removal around Knowle has its own page with the full story — including why it is often the more serious of the two. Unfamiliar locations are where this occurs most, and the reason is mechanical not careless: the narrower petrol nozzle goes into a modern diesel filler neck with almost no resistance at all. Topped up near Venture Hall without thinking, in a diesel Mercedes A-Class you have had for two days? Ring us where you are. Hire and courtesy cars tend to get driven further before anyone spots it, and miles is what determines how much petrol gets to your injectors. ## What a petrol-in-diesel fuel drain will cost around Knowle We can't put one price on this page honestly, as the job isn't one job. What shifts it: - This is the main one: whether your motor has been run, or driven. - How much of the wrong fuel went in, set against how much the tank can hold. - Whether it's petrol or AdBlue. - Where your car is, and whether our van can sensibly get to and work on it. Tell us the vehicle, the amount and whether it has run, and you will get a straight answer instead of a range. Not time-critical, with your car at home and going nowhere? Then does the job. Flushed, not emptied — that's what a diesel Renault Captur which got as far as Budleigh Salterton Football Club needs. Running a diesel puts that blend into your filter, the lines, the pump and the rail, none of which empties with that tank, so by now that tank holds the smaller part of the problem. ## Knowle drivers ask us these about petrol in diesel ## Fuel drains on a Knowle petrol station forecourt Yes — forecourts are where a big part of this takes place. We attend East Budleigh Garage and the other forecourts locally all the time, with the station's agreement — tell us which one you're at when you phone and we will tell you whether our engineers can work there. ## How much petrol in a diesel is too much? Whether the motor has run counts a lot more, though the proportion matters too, rather than the litres. Five litres into an almost dry tank is not five into a full one, no. But both land on the same question in the end: has that blend been drawn right through, or has it not? ## Petrol in my diesel, and I have driven the vehicle Stop sensibly. Off. Nothing after that. Driving is what takes the problem from the tank into the pump and injectors — but it's salvageable far more often than drivers expect, and the single most valuable thing you can do now is not restart the vehicle. ## Is a fuel drain going to void my warranty? A drain and flush carried out properly is not a change and doesn't void a manufacturer's warranty. Running a diesel on petrol is the thing likelier to cause an argument with one, which is another reason to leave the car turned off. ## Adding two-stroke oil, then driving home What petrol has weakened isn't replaced by two-stroke oil, which is an old remedy for a separate fault. So no. The pump still has to cope with it, because the tank still has petrol in it later on. ## Does petrol in a diesel have to go to a main dealer? Wherever the car is, our technicians drain and flush it there, so a visit to the main dealer does not come into it. ## You, and your vehicle, still together? Leave the car shut off. Switch it off somewhere safe and leave it off, if you have already driven it. Cold, stationary, going nowhere: that is the best place to be in. Drivers fear this much more than they need to. At the kerbside, on the forecourt or at home — mobile fuel draining around Knowle and across Devon.