--- title: Explained: AdBlue in a Diesel Tank New Downs canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/new-downs-cornwall/ location: New Downs county: Cornwall latitude: 50.124940 longitude: -5.687970 service: AdBlue in a Diesel Tank updated: 2026-10-08 --- # How It Happens and How to Prevent It: AdBlue in a Diesel Tank in New Downs Keep your motor and ignition off and ring 0333 366 0103 now — reading can wait if AdBlue is already in the diesel tank. Around New Downs, catching it before the engine turns usually leaves draining and a full flush where it stands. Not happened yet? Further down, the rest of the page covers the reasons it happens and the how to prevent it for good. ## AdBlue in a diesel vehicle: two tanks, two fillers No single liquid but two: that's how plenty of newer diesels around New Downs and Higher Bosavern carry, with diesel for your engine. Kept in a tank of its own, AdBlue is fed into your exhaust gas and cleans it. Each tank has its own filler. Other vehicles put the AdBlue filler in the boot or under the bonnet; plenty more have the two together behind one flap. Topping up your diesel side at the petrol pump happens constantly. Much less regularly, the AdBlue side gets topped up — normally from a bottle, by someone working out where it goes. It's in that gap that the error lives. ## AdBlue in the diesel tank around New Downs: how it takes place Three things tend to line up, and carelessness is rarely one of them. The warning comes first. As AdBlue runs low the vehicle tells you, and if it runs out completely, your vehicle goes into limp mode. So the top-up is done in a hurry: on a driveway off Cape Close before work, or in the car park outside Commercial Hotel on the way home. The old car's filler is where your hand goes — but a hire car, a new car or a company car keeps the fillers somewhere else. That's the second thing: a strange car. No part halts the tip after it has started, since a bottle with a spout goes into a diesel filler as readily as an AdBlue one. The bottle fits. St Just or the heart of New Downs: it takes the same few seconds either way. ## The AdBlue filler and your diesel filler: telling them apart Before you tip anything, whether on a driveway in Tregeseal or a forecourt around New Downs, check these. They take a few seconds. - Check the cap rather than going by where it sits: AdBlue caps are often blue or marked "AdBlue", and diesel ones usually aren't. - Check the size: the smaller neck is, on many motors, the AdBlue one. - A label inside the fuel flap frequently says which fuel goes where, on plenty of cars. Check for it. - The handbook. If the filler isn't by your diesel cap, it's in your boot or under the bonnet, and the handbook says which. - The previous driver knows. Check when you pick up a rental or company car — from Penzance's car park, perhaps — rather than once the light comes on. ## How to top up without AdBlue in your diesel tank A routine for the day the light comes on, wherever in Cornwall that is. - Stop somewhere level, engine off, with time in hand — not rushing on the side of Carn Gloose Road. - Say "AdBlue" out loud as you unscrew the cap, after finding the AdBlue filler and read it. Daft, perhaps, but it works. - Leave the diesel cap on. If both sit under one flap, check the diesel cap is still closed before you lift 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 your diesel cap was never opened. Only then start your car. Discover at the second or third stage that the bottle went into the wrong filler? That's where you stop. Don't go on to step five. ## Put AdBlue in the diesel tank around New Downs already? Then the order of things is short. Do not start the motor. The fuel pump starts on plenty of diesels as soon as your ignition is switched on — so keep it off. Thinning it with extra diesel won't work, since AdBlue settles to the bottom instead of mixing — and that is where the fuel is sucked from. Ask the attendants to help push the vehicle clear of the petrol pump if you are at a forecourt — the Trewellard Garage, the Gulf or anywhere else. If you are on your own driveway in New Downs, leave the car where it stands. Already started? Stop once it's safe, then turn off. New Downs sits over 50 miles from the M5; on it, take the next junction. Tell us roughly how far it went: a run towards Truro, under 50 miles away, is a bigger job than a short hop across New Downs. ## New Downs: what happens when we turn up Our engineers come to the car wherever it has stopped, whether that is outside St Just Primary School, close to St Just Methodist Church or on your own driveway. What fluid got in, the amount, and if it ran: we ask because those replies set both work and quote. That quote is given on the call, ahead of any van leaving. The fuel system is then purged thoroughly, once your tank is cleared. 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 doesn't wash out on its own. A test is at the end: before that, fresh diesel is added, and the filter is cleaned or changed as needed. We don't leave until it has been started and is running smoothly. With pumps fine on a busy forecourt and quiet enough to use outside a house at night, most jobs in which the engine has not run need about half an hour after our technicians arrive. Paying happens on the day, not upfront, and you receive the documents an insurer wants: an engineer report and a VAT invoice. Wrong-fuel cover is part of many insurance policies — so make use of the wait to check yours. ## About New Downs, briefly New Downs is a coastal locality in Cornwall, situated near the towns of St Just and Bosorne, with Boscean also nearby. New Downs sits at an elevation of 111 metres, overlooking the surrounding coastline. New Downs is characterized by its predominance of terraced housing, typical of many Cornish settlements. New Downs is located approximately 29.8 miles from Truro, the nearest city. ## AdBlue drains across Cornwall, New Downs included Being a coastal area, New Downs shares its vans nearby places — Bosorne, Boscean — all the way through TR postcodes and the surrounding area beyond. A postcode starting TR19 7 gets our van to you fastest. The vehicle does not need to shift. A drive, a lay-by on the way to St Just Cricket Club, a side street close to Methodist Free Church: our technicians drain it where it sits. Ring and ask rather than guessing if you're close to a border, or somewhere hard to describe, like the back of Lafrowda Park. ## For New Downs drivers, the short version Tip nothing till you've read the cap. Still AdBlue in your diesel tank? Petrol in Diesel will empty it where it is, anywhere around Cornwall: switch it off and phone 0333 366 0103.