--- title: Explained: AdBlue in a Diesel Tank Gerrards Cross canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/gerrards-cross-buckinghamshire/ location: Gerrards Cross county: Buckinghamshire latitude: 51.587350 longitude: -0.554260 service: AdBlue in a Diesel Tank updated: 2026-10-09 --- # Gerrards Cross: How Does AdBlue End Up in a Diesel Tank, and How Do You Prevent It? If AdBlue is already in your diesel tank, stop reading for a moment: leave the motor and your ignition off then ring 0333 366 0103. Usually, if your motor has not run, it's drained and fully flushed where your car is around Gerrards Cross. The remainder of this page covers why it happens and how to make sure it does not — useful if you are reading before it has happened. ## Two fillers, two tanks: AdBlue in a diesel motor Plenty of modern diesels on the roads around Gerrards Cross and Layters Green carry two liquids, not one. Diesel goes to your engine. Its own tank keeps it, and from there it goes to your exhaust, and there a spray cleans the gas. Every tank has one filler of its own. Under one flap, side by side: that's the arrangement on a lot of motors. On others, AdBlue's filler sits beneath the bonnet or in your boot instead. The diesel side is fuelled at the pump all the time. Far less commonly, the AdBlue side is topped up — normally from a bottle, by a person working out where it goes. It's in the gap that the error lives. ## Gerrards Cross: how AdBlue in the diesel tank happens It is rarely carelessness. Three things tend to line up. On a drive off Bulstrode Way before work, or in the car park at Ethorpe Hotel heading home: that's where the rushed top-up happens. Why the rush? As AdBlue runs low your car warns you, and once it's gone, limp mode kicks in. Then your car is unfamiliar. A hire car, a new car or a company car puts the fillers where your last one didn't, and the hand hits for the cap it would have used on the old one. And the bottle fits. A bottle with a spout goes into a diesel filler as easily as an AdBlue one, and so nothing stops the tip after it has started. Whether it happens in Austenwood or the middle of Gerrards Cross, it is the same few seconds. ## The AdBlue filler and the diesel filler: telling them apart Whether a Gerrards Cross forecourt or a driveway out in Hedgerley Green, spend a couple of seconds over these before any goes in. - The cap. The AdBlue cap is often blue, or marked "AdBlue". Your diesel cap usually is not. Read it instead of going by where it sits. - The size. On many cars the AdBlue filler neck is the smaller of the two. - The flap. Look inside your fuel flap for a label. Many motors say there which fuel goes where. - In the boot or under the bonnet: that is where your filler sits if it's not by the diesel cap, and the handbook tells you which. - The previous driver knows. Ask when you pick up a rental or company car — at the nearest station's car park, perhaps — rather than when the light appears. ## Topping up AdBlue without it reaching the diesel tank A routine for the day the light comes on, wherever across Buckinghamshire that is. - Turn off once parked — level ground, engine stopped, and never in a rush beside Marsham Way at the roadside. - Silly as it sounds, saying "AdBlue" aloud as you unscrew the cap does the trick — after you have located your filler and read it. - The diesel cap stays on. Where both sit under a flap, confirm it is shut before the bottle comes up. - Pour slowly, using the bottle's own spout. Stop when it's full or when the bottle is empty. - Only after that, start the car: close the cap, check a second time, and make sure your diesel cap was never opened. Spot at step two or three that it's already gone into your diesel side? So stop just there. Leave out stage five altogether. ## AdBlue in the diesel tank already, around Gerrards Cross? What follows is a short order of things, starting with not starting your engine. On many diesels your ignition alone runs the fuel pump, and so don't switch it on. Diluting it with extra diesel won't work, since AdBlue sinks to the bottom instead of blending — and that's where your fuel is drawn from. If you're at a forecourt, whether it's the BP or the another forecourt nearby, ask the attendants to help push the vehicle clear of the pump. On your own drive in Gerrards Cross? So your car stays put. Already run? Pull over once it is sensible, then turn off. On the M25, under a mile from Gerrards Cross, that means the next exit. A short hop across Gerrards Cross is a smaller job than a run towards St Albans, under 15 miles away, so tell us about how far it went. ## Our arrival around Gerrards Cross, and what occurs next Anywhere the car came to rest, whether outside The Gerrards Cross CofE School, near Everyman or at home, our van comes to it. What fluid went in, the quantity, and if it ran: our technicians ask because the replies set the work and quote. The quote comes over the phone, before any van leaves. The system is then cleaned thoroughly, once that tank is emptied. 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 doesn't wash out on its own. Your filter is cleaned, or replaced where it needs to be; fresh diesel goes in; and the vehicle is tested. Your engine is fired up next and tested to be sure it runs smoothly, all before we go. Unstarted vehicles mostly mean a half-hour job after the moment we arrive. The kit is fine on a busy forecourt, and quiet enough for a driveway after dark. You pay on the day, with nothing upfront, and get a VAT invoice and an engineer report for your insurer. While we travel, take a look at your policy; plenty carry cover for misfuelling. ## About Gerrards Cross itself Gerrards Cross is a town situated in a riverside location in Buckinghamshire, England, with the River Misbourne flowing nearby. It is nestled at the foot of the Chiltern Hills, providing a scenic backdrop to the town. Gerrards Cross is conveniently located near major roads, including the M25 and M40 motorways, and is close to several neighbouring villages. The town's history dates back to ancient times, with evidence of Iron Age settlements in the area. ## AdBlue drains across Buckinghamshire, Gerrards Cross included Being a riverside town, Gerrards Cross shares its vans surrounding places — Chalfont St Peter, Tatling End — right across SL postcodes and the surrounding area around them. A postcode starting SL9 7 gets the van to you fastest. No need to shift your car. Draining happens on the spot, be it a drive, a street by Gerrards Cross Community Library, or a lay-by on the way to Gerrards Cross Community Association. If you're near a border, or somewhere hard to describe like the back of Gerrards Cross Methodist Church, ring and ask instead of guessing. ## Gerrards Cross motorists: the short version Tip nothing till you've read the cap. Even so AdBlue in the diesel tank? Petrol in Diesel can empty it wherever it is, wherever around Buckinghamshire: keep the vehicle off and ring 0333 366 0103.