--- title: Highgate: AdBlue in a Diesel Tank, Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/highgate-east-sussex/ location: Highgate county: East Sussex latitude: 51.090310 longitude: 0.033780 service: AdBlue in a Diesel Tank updated: 2026-10-07 --- # Preventing AdBlue in a Diesel Tank in Highgate: Why It Occurs Stop reading for a moment if your diesel tank already holds AdBlue in it: ignition off, engine off, then call 0333 366 0103. A drain and a thorough flush, done just where your car sits around Highgate, is usually all it takes when caught before the engine runs. If you're reading before it has happened, the rest of this page is about why it occurs and how to make sure it does not. ## AdBlue in a diesel vehicle: two tanks, two fillers Diesel goes to the engine — but plenty of current diesels driven round Highgate and Ashurst Wood hold a second liquid as well. Your exhaust, not your motor, is where AdBlue goes: sprayed into the fumes to clean them, from a separate tank. Each tank has its own filler. Plenty of motors have a single flap for the two, whereas others move the AdBlue filler to your boot or under the bonnet. The diesel side is topped up at the petrol pump all the time. The AdBlue side is topped up far less frequently, usually from a bottle, and usually by somebody who has to stop and think where it goes. The mistake grows in that gap between them. ## How does AdBlue in your diesel tank occur in Highgate? Rarely is it carelessness: normally three things coincide. The warning comes first. As AdBlue runs low the vehicle tells you, and if it runs out completely, the car drops into limp mode. So the top-up is done in a hurry: on a driveway off Inkpen Lane before work, or in the car park at The Chequers on the way home. New-to-you motors come second, too. Rentals, new cars and company motors place their fillers differently, and habit goes for the cap it used on the old one. Nothing halts the pour once it has started, because a bottle with a spout goes into a diesel filler as readily as an AdBlue one. The bottle fits. It takes seconds, whether out in Tompsets Bank or right in the centre of Highgate. ## Telling the AdBlue filler from your diesel filler Look at these first, at a forecourt around Highgate or a driveway out in Wych Cross. A few seconds, that's all. - The cap. The AdBlue cap is regularly blue, or marked "AdBlue". Your diesel cap normally isn't. Read it instead of going by where it sits. - Plenty of motors give AdBlue the smaller filler of the two. - The flap. Look inside the fuel flap for a label. Many vehicles say there which fuel goes where. - The handbook. If your filler isn't by the diesel cap, it is in the boot or under the bonnet, and the handbook says which. - Ask the person who drove it last — before you leave, not when the light comes on — when you pick up a hire or company car from somewhere like the car park outside East Grinstead. ## Topping up AdBlue without it reaching your diesel tank A routine for the day the light comes on, wherever around East Sussex that is. - Turn off after you park — level ground, engine stopped, and never rushed beside Highgate Road at the roadside. - Silly as it sounds, speaking "AdBlue" out loud while you unscrew the cap works — after you've found the filler and read the cap. - The diesel cap stays on. Where the two share a flap, make sure it is closed before lifting the bottle. - Gently does it, through the bottle's own spout, till it's full or the bottle runs out. - Before you start the vehicle, close the cap and look again that the diesel cap was never opened off. Stop there if you find, at stage two or three, that you've already poured into your diesel side. Skip stage five entirely. ## Highgate: already put AdBlue in the diesel tank? Short list, then. Top of that: your engine remains unstarted. Keep the ignition off too, because on plenty of diesels it alone starts your pump. Thinning it with more diesel won't work, since AdBlue settles to the base rather than mixing — and that is where the fuel is sucked from. If you're on a forecourt, whether it's the Tesco or the JET, ask the attendants to help push the car clear of the petrol pump. On your own drive around Highgate? Then the car stays where it is. When the motor has run by now, pull over somewhere safe then turn the vehicle off. The next junction means where to leave if you're on the M23, under 10 miles from Highgate. About how far did it go? Crossing Highgate is smaller work than a run of under 25 miles towards Brighton and Hove, so tell us. ## What takes place when we turn up in Highgate Anywhere the car has stopped, whether outside Forest Row Church of England Primary School and Nursery, beside The Venu or on your own drive, our van travels to it. Both the work and the quote depend on three replies — what fluid, what quantity, and if it has run — so we ask. Nobody sets off before you've had our quote by phone. Emptying your tank comes next, then a thorough flush of the fuel system. AdBlue crystallises and is corrosive to some of the metals in a fuel system, and so it doesn't wash out on its own — which is why that matters more here than with petrol. Once the fuel filter is flushed — or replaced, if needed — fresh diesel goes in, and then the car gets tested. We do not leave until it has been started and is running properly. Unrun cars mostly mean a half-hour visit after arrival. The kit is fine on a busy forecourt, and quiet enough for a residential street late at night. No money upfront; you settle up on the day. Afterwards, the VAT invoice and the report from the engineer are handed to you for your insurer. Plenty of insurance policies include misfuelling cover, so it is worth checking yours while we're on the way. ## About Highgate and where it is Highgate is a suburban area in East Sussex, situated inland at an elevation of 82 metres, and is located near Tompsets Bank and Forest Row. Highgate is characterized by its predominantly detached housing stock, reflecting the area's residential nature. Highgate sits within the wider South East region, approximately 20 miles from Brighton and Hove and 29.7 miles from London. Highgate remains a small, quiet community with a population of around 1999 residents. ## Highgate and East Sussex: AdBlue drains across the area Highgate is a residential suburb, and the teams that cover it also work the towns near it, Forest Row and Quabrook among them, across the RH postcode area. The van gets to you fastest with a postcode starting RH18 5. Moving the vehicle isn't necessary. Our technicians drain it where it is — a side street close to Christian Community Church, a lay-by on the way to Rush Green, a drive. Ring and ask instead of assuming if you're near a boundary, or somewhere hard to explain, like the back of Forest Row Parish Council & Community Centre. ## In short, for Highgate people Always, the cap; after that, the pour. Even so AdBlue in the diesel tank? Petrol in Diesel can empty it where it is, wherever around East Sussex: switch the vehicle off then call 0333 366 0103.