--- title: Explained: AdBlue in a Diesel Tank Cheshunt canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/cheshunt-hertfordshire/ location: Cheshunt county: Hertfordshire latitude: 51.702620 longitude: -0.042760 service: AdBlue in a Diesel Tank updated: 2026-10-11 --- # Avoiding AdBlue in a Diesel Tank in Cheshunt: Why It Happens If AdBlue is already in your diesel tank, stop reading for a moment: leave the engine and the ignition off and call 0333 366 0103. A drain plus a full flush, carried out right where the car stands around Cheshunt, is normally all it needs if found before your engine runs. The remainder of this page explains why it takes place and how to ensure it does not — useful if you are reading ahead of time. ## AdBlue in a diesel car: two tanks, two fillers Plenty of newer diesels in Rosedale, like those in Cheshunt, run on two liquids; the engine gets just the diesel. AdBlue goes to the exhaust, where it is sprayed into the gas to fresh it, and it lives in a tank of its own. Every tank has one filler of its own. Plenty of motors share a single flap for the two, while others move the AdBlue filler to the boot or under the bonnet. Diesel goes in at each filling station visit, week in, week out. Far less regularly, the AdBlue side gets topped up — normally from a bottle, by someone working out where it goes. The mistake grows in that gap between them. ## AdBlue in the diesel tank in Cheshunt: how it occurs Rarely is it carelessness: usually three things line up. The warning comes first. As AdBlue runs low your car tells you, and if it runs out completely, the vehicle drops into limp mode. So the top-up is done in a hurry: on a drive off College Road before work, or in the car park outside The Crocodile on the way home. New-to-you cars are second, too. Rentals, new vehicles and company cars place their fillers differently, and habit reaches for the cap it 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 pour once it has started. It takes a few seconds, whether in Churchgate or right in the centre of Cheshunt. ## The AdBlue filler and your diesel filler: telling them apart Before you pour anything, whether on a drive in Waltham Cross or a forecourt around Cheshunt, check these. They take a few seconds. - Read the cap instead of going by where it sits: AdBlue ones are often blue or marked "AdBlue", and diesel ones usually are not. - The size. On many vehicles the AdBlue filler neck is the smaller of the two. - Check inside the fuel flap: many vehicles carry a label there saying which fuel goes where. - In the boot or under the bonnet: that's where your filler is if it's not by your diesel cap, and the handbook says which. - The person who drove the vehicle last. On a hire or company car picked up from somewhere like the car park at Theobalds Grove, ask before you leave, not when the light comes on. ## AdBlue top-ups that never reach your diesel tank A routine for the day the light comes on, wherever across Hertfordshire that is. - Park and switch off. Not on a slope, not with your motor running, and not in a rush on the side of Great Cambridge Road. - Find the AdBlue filler and read the cap. Say "AdBlue" out loud as you unscrew it. It sounds daft and it does the trick. - Leave your diesel cap on. If both sit under one flap, check your diesel cap is still closed before you lift the bottle. - Pour slowly, using the bottle's own spout. Stop when it is full or when the bottle is empty. - Only then, start your car: close the cap, check a second time, and make sure your diesel cap was never opened. Find at stage two or three that it's already gone into your diesel side? So stop right there. Don't go on to stage five. ## Cheshunt: already put AdBlue in your diesel tank? Don't start your motor: that is where the short order of things starts. The fuel pump starts on many diesels the moment your ignition is switched on — and so leave it off. Filling up with diesel will not weaken it: rather than mixing, AdBlue drops to the bottom of your tank, just where the fuel is drawn from. The attendants at BP, Shell or any forecourt will usually lend a hand pushing the car away when asked. If you are on your own drive around Cheshunt, leave the car where it is. Where your motor has been run already, pull over somewhere safe then switch the vehicle off. On the M25, under 3 miles from Cheshunt, that means the next junction. A short hop across Cheshunt is a smaller job than a run towards St Albans, under 15 miles away, and so tell us about how far it went. ## Our arrival around Cheshunt, and what happens next Our engineers come to the vehicle wherever it has stopped, whether that's outside Burleigh Primary School, near Bishops' College or on your own driveway. Which fluid went in, the quantity, and whether it ran: our engineers ask since those answers set both work and quote. That quote comes on the call, before any van leaves. Your system is then rinsed thoroughly, once your tank is drained. Unlike petrol, AdBlue leaves crystals and attacks some fuel-system metals, and none of that clears out by itself. Hence it matters more. The filter is cleaned, or replaced where it needs to be; fresh diesel goes in; and your car is tested. Before we go, our technicians fire it up and check that it's running properly. If your engine hasn't run, most jobs take about half an hour once we are there, using pumps that are safe on a working forecourt and quiet enough to use outside a house at night. Paying is on the day, not upfront, and you receive the documents your insurer asks for: an engineer report and a VAT invoice. While we travel, have a look at your insurance documents; many carry cover for misfuelling. ## About Cheshunt, for a moment Cheshunt is a town in Hertfordshire, situated on the River Lea, with a mix of terraced housing and other residential areas. Cheshunt sits at a relatively low elevation of around 30 metres, close to the borders of Essex and within commuting distance of London. Cheshunt has a number of nearby neighbourhoods, including Churchgate, Bury Green, and Flamstead End. Cheshunt is home to a population of approximately 31,886 people. ## Cheshunt and Hertfordshire: AdBlue drains across the area Cheshunt is a riverside town, and our vans that cover it also work the places around it, Bury Green and Flamstead End among them, across the EN postcode area. Quote a postcode beginning EN8 8, and our van arrives quickest. Your car stays put. A driveway, a lay-by on the way to Whit Hern Park, a side street near Saint Mary the Virgin Church: our technicians drain the car where it stands. Awkward to pin down, like the back of Saint Paul's Church? By a county line? Asking beats assuming, and so ring. ## Cheshunt motorists: the short version Pour nothing until you have read the cap. Still AdBlue in your diesel tank? Petrol in Diesel can empty it where it stands, wherever in Hertfordshire: switch the car off and ring 0333 366 0103.