--- title: Knowle: AdBlue in a Diesel Tank, Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/knowle-devon/ location: Knowle county: Devon latitude: 50.636460 longitude: -3.342480 service: AdBlue in a Diesel Tank updated: 2026-10-22 --- # AdBlue in a Diesel Tank in Knowle: Why It Happens and How to Avoid It Stop reading a minute if the diesel tank already holds AdBlue in it: ignition off, engine off, then ring 0333 366 0103. Around Knowle, catching it before the motor runs normally leaves draining and a thorough flush where it stands. Here before the event? Then what follows explains why it happens and how to stop it ever happening. ## AdBlue in a diesel motor: two tanks, two fillers Diesel goes to your engine — yet plenty of current diesels driven round Knowle and East Budleigh hold a second fluid too. Your exhaust, not your engine, is where AdBlue goes: dosed into the fumes to fresh them, from a separate tank. There is a filler for each tank. Other cars keep the AdBlue filler in the boot or under the bonnet; plenty more place both side by side under one flap. The diesel side is fuelled at the petrol pump all the time. The AdBlue side is fuelled far less often, usually from a bottle, and normally by someone who has to stop and think where it goes. Mistakes happen in the gap between the two. ## How AdBlue in your diesel tank takes place around Knowle It's hardly ever carelessness. Three things tend to line up. The warning comes first. As AdBlue runs low your car tells you, and if it runs out altogether, the car drops into limp mode. So the top-up is done in a hurry: on a driveway off Knowle Road before work, or in the car park outside Dog & Donkey on the way home. The old car's cap is where your hand goes — yet a hire car, a new vehicle or a company car puts the fillers somewhere else. That's the second factor: an unfamiliar motor. A spout-topped bottle meets no resistance at a diesel filler any more than at an AdBlue one. So the pour, after begun, carries on. The same few seconds settle it, in the middle of Knowle or out in Budleigh Salterton. ## The AdBlue filler and the diesel filler: telling them apart A couple of seconds is all these take — so check them before you tip anything, on a driveway in Littleham or a forecourt around Knowle. - Read the cap instead of going by position: AdBlue caps are commonly blue or marked "AdBlue", and diesel caps normally are not. - The size. On many motors the AdBlue filler neck is the smaller of the two. - The flap. Look inside the fuel flap for a label. Many cars say there which fuel goes where. - The handbook shows which it lives if the filler is not next to your diesel cap: your boot, or under the bonnet. - The previous driver knows. Check when you collect a hire car or company car — at Exmouth's car park, perhaps — not when the light comes on. ## How to top up without AdBlue in your diesel tank Wherever around Devon the light comes on, this is a routine for that day. - Turn off after you park — level ground, motor stopped, and never rushed by Dalditch Lane at the roadside. - Silly as it sounds, speaking "AdBlue" out loud while you unscrew the cap does the trick — once you have located your filler and read the cap. - The diesel cap remains on. Where both share a flap, make sure it's closed before lifting the bottle. - Using the bottle's own spout, pour slowly — and stop when it is full or the bottle is empty. - Close the cap and check again. Make sure the diesel cap was never opened. Only then start the vehicle. Stop there if you find, at step two or three, that you have already poured into the diesel side. Do not go on to step five. ## Knowle: already put AdBlue in your diesel tank? Brief list, then. First: your engine stays unstarted. The fuel pump runs on plenty of diesels as soon as the ignition goes on — and so keep it off. Thinning it with more diesel fails, since AdBlue settles to the bottom rather than mixing — and that's where the fuel is pulled from. Ask the attendants to help push the car away from the petrol pump if you are at a forecourt — the Pace, the East Budleigh Garage or somewhere else. If you're on your own drive in Knowle, leave it where it sits. Stop as soon as it is safe then switch off, if your engine has already run. On the M5, under 10 miles from Knowle, that means the next exit. Mileage matters — a short hop across Knowle makes a smaller job than driving under 15 miles to Exeter — so say about how far it went. ## Knowle: what occurs when our engineers arrive Outside St Peter's Church of England Primary School, near Knowle Village Hall or on your own drive: wherever your car has stopped, our technicians come to it. The answers decide the work and the price, so we ask what was put in, about how much, and whether it's run. You hear that quote on the phone, before anyone heads out. Draining that tank comes next, then a thorough flush of the system. With AdBlue that counts more than with petrol: it crystallises and is corrosive to some of the metals in a fuel system, and so it does not wash out on its own. Once the filter has been cleaned — or renewed, if needed — clean diesel goes in, and finally the car is tested. We do not go until it has been started and is running correctly. If your engine hasn't run, most jobs take about half an hour once we're there, using pumps that are fine on a working forecourt and quiet enough to use outside a house after dark. Paying happens on the day, not upfront, and you are given the documents an insurer asks for: an engineer's report and a VAT invoice. Wrong-fuel cover is included in plenty of insurance policies — so make use of the wait to look at yours. ## About Knowle itself 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. ## Knowle and Devon: AdBlue drains across the area Knowle is a coastal village, and the teams that cover it also work the places around it, Little Knowle and Kersbrook among them, across the EX postcode area. Give a postcode beginning EX9 6, and our van gets there fastest. Moving the car isn't necessary. A driveway, a lay-by on the way to Leeford Plantations, a side street near Venture Hall: our technicians drain the car where it sits. Guessing won't help behind Budleigh Salterton Football Club, on a border, or somewhere awkward to describe; phone and check. ## For Knowle motorists, the short version Tip nothing until you have read the cap. If AdBlue has gone in your diesel tank regardless, leave the vehicle off and phone 0333 366 0103. Petrol in Diesel clears it where it stands, anywhere across Devon.