--- title: Explained: AdBlue in a Diesel Tank Oakley canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/oakley-buckinghamshire/ location: Oakley county: Buckinghamshire latitude: 51.804320 longitude: -1.074950 service: AdBlue in a Diesel Tank updated: 2026-10-24 --- # How It Happens and How to Avoid It: AdBlue in a Diesel Tank in Oakley Pause here a minute when the diesel tank already has AdBlue in it: ignition off, engine off, and call 0333 366 0103. Caught before your motor runs, it is normally a drain and a thorough flush, done where the car is in Oakley. Here before the event? Then the rest covers how it comes about and what to prevent it ever happening. ## Two fillers, two tanks: AdBlue in a diesel car Diesel goes to the motor — yet plenty of newer diesels seen round Oakley and Boarstall hold a second fluid as well. Stored in a tank of its own, AdBlue is sprayed into the exhaust stream and cleans it. Each tank has its own filler. Other motors put the AdBlue filler in the boot or under the bonnet; a lot more place both together under one flap. Diesel gets filled at every forecourt call-out, week in, week out. Far less often, the AdBlue side is topped up — mostly from a bottle, by someone thinking about where it goes. The mistake grows in the gap between the two. ## How does AdBlue in your diesel tank occur in Oakley? Three things tend to line up, and carelessness is seldom one of them. On a drive off Oxford Road before work, or in the car park outside The Chandos Arms on the way home: that's where the hurried top-up happens. Why the rush? As AdBlue gets low the vehicle warns you, and if it's gone, limp mode kicks in. Then, the hand reaches for the cap it knew on the old car — since a hire car, a new vehicle or a company car places the fillers where your last one did not. Third, the spout fits: diesel filler or AdBlue one, it goes in as easily, and once the pour starts, no part stops it. Whether it takes place in Little London or the middle of Oakley, it is the same few seconds. ## How to tell the AdBlue filler from the diesel one Be it a Oakley forecourt or a drive out in Worminghall, spend a few seconds on these before any goes in. - Blue and marking: an AdBlue cap is commonly blue, or says "AdBlue", where a diesel cap usually doesn't. Trust the cap, not where it sits. - Check the size: the smaller filler neck is, on many vehicles, the AdBlue one. - Look inside the fuel flap: plenty of motors carry a label there showing which fuel goes where. - Cannot see it beside the diesel filler? In that case check beneath the bonnet or inside the boot — the owner's manual will say where. - Whoever had it before will know. Check when you collect a hire car or company car — at Haddenham & Thame Parkway's car park, perhaps — rather than once the warning appears. ## AdBlue top-ups that never reach your diesel tank Anywhere around Buckinghamshire the light comes on, this is a routine for the day. - Not in a rush on the side of Manor Road, not on a slope, not with the motor running: park then switch off first. - Find the AdBlue filler and read the cap. Say "AdBlue" out loud as you unscrew it. It sounds silly and it does the trick. - The two under one flap? So make sure the cap on your diesel filler is still closed before raising the bottle. - Using the bottle's own spout, tip slowly — and stop when it is full or the bottle is empty. - Before you start the car, shut the cap and look a second time that your diesel cap was never opened off. If at stage two or three you find you have already poured into your diesel side, stop there. Step five is out. ## Oakley: already put AdBlue in the diesel tank? The short order of things, beginning with no starting the engine. Leave the ignition off too, because on many diesels switching it on by itself runs your fuel pump. AdBlue does not mix with diesel — it sinks to the bottom of the tank, where your fuel is pulled from — so don't top up with diesel to thin it. The staff at Asda, BP or another forecourt will normally help pushing the car away when asked. Your own driveway around Oakley is the place it should stay. If your engine has already run, stop as soon as it is safe then switch off. The next junction is the place to leave if you are on the M40, under a mile from Oakley. Tell us about how far it went: a run towards Oxford, under 10 miles away, is a bigger job than a short hop across Oakley. ## What takes place when we get there in Oakley Wherever the vehicle came to rest, whether by Oakley Church of England Combined School, beside Oakley Village Hall or on your own drive, the van travels to it. Which fluid went in, the amount, and if it ran: we ask because the replies set the work and quote. Nobody heads out until you've heard our quote over the phone. Then that tank is drained and your system flushed thoroughly. With AdBlue that matters 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. Testing comes at the end: before that, clean diesel is added, and the filter is cleaned or changed as needed. Before we go, our engineers fire it up and make sure that it's running properly. If the motor hasn't run, the majority of jobs take about half an hour once we are there, using pumps that are safe on a busy forecourt and quiet enough to use outside a house at night. No money upfront; you settle up that day. Afterwards, a VAT invoice and the report from the engineer are handed to you for the insurer. Many insurance policies include misfuelling cover, so it is worth checking yours whilst we are on the way. ## About Oakley Oakley is a small village in Buckinghamshire, situated inland at an elevation of 86 metres, approximately 8.6 miles from Oxford. Oakley has a population of around 683 people and is characterised by semi-detached housing. Oakley is located near other villages such as Little London, Honeyburge, and Brill, and is about 45.5 miles from London. ## AdBlue drains around Oakley, and Buckinghamshire beyond Oakley is a rural village, and the vans that cover it also work the towns around it, Honeyburge and Brill among them, across the HP postcode area. Fastest of all: quote a HP18 9 postcode to the van. Moving the car is not needed. Anywhere it stands — beside Saint Mary, in a layby en route to Boarstall Wood, on a drive — that is where it gets emptied. Awkward to pin down, like the back of Brill Memorial Hall? By a county line? Checking is better than guessing, and so phone. ## The short version for Oakley motorists Before you tip, read the cap. If AdBlue has gone in the diesel tank anyway, leave the car off and ring 0333 366 0103. Petrol in Diesel drains it where it stands, anywhere around Buckinghamshire.