--- title: Week St Mary: AdBlue in a Diesel Tank, Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/week-st-mary-cornwall/ location: Week St Mary county: Cornwall latitude: 50.749900 longitude: -4.500680 service: AdBlue in a Diesel Tank updated: 2026-10-25 --- # Why It Happens and How to Avoid It: AdBlue in a Diesel Tank in Week St Mary 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 and a full flush, done just where the car sits around Week St Mary, is normally what it needs when found before your motor runs. The remainder of this page covers why it takes place and how to make sure it doesn't — useful if you're reading before it has happened. ## Why does AdBlue in a diesel car need its own filler? Plenty of modern diesels around Treskinnick Cross, like those in Week St Mary, run on two fluids; the motor gets just the diesel. Kept in a tank of its own, AdBlue is fed into your exhaust stream to clean it. Each tank has one filler of its own. Other motors keep the AdBlue filler in the boot or under the bonnet; plenty of others have the two together under one flap. At the petrol pump, the diesel side gets filled constantly. Seldom filled, AdBlue usually goes in from a bottle, poured by someone who has to stop and think which cap it needs. Mistakes happen in that gap between the two. ## How AdBlue in the diesel tank happens in Week St Mary Carelessness rarely explains it. What does is three things coming up at once. First, the warning. Low AdBlue brings a message from the vehicle, and letting it run dry leads to limp mode — so a rushed top-up, perhaps before work off Ashbury Grove, or at the pub in the village on the way home after work. Then, your hand reaches for the cap it would have used on the old motor — because a hire car, a new vehicle or a company car places the fillers where your last one didn't. A spout-topped bottle meets no obstacle at a diesel filler any more than at an AdBlue one. And so the pour, once started, carries on. Week Green or the heart of Week St Mary: it takes the same few seconds either way. ## Telling the AdBlue filler from your diesel filler A few seconds is all these take — so run through them before you pour anything, on a driveway in Poundstock or a forecourt in Week St Mary. - Where it sits misleads; the cap does not. AdBlue caps tend to be blue or carry the word "AdBlue" — diesel caps normally do not. - On plenty of cars, the size gives it away: AdBlue has the smaller filler neck. - The flap. Look inside your fuel flap for a label. Plenty of cars say there which fuel goes where. - In your boot or under the bonnet: that's where the filler sits if it's not by the diesel cap, and the handbook says which. - Collecting a hire or company car, perhaps at the car park outside the nearest station? Ask whoever drove it last before leaving, rather than when the light comes on. ## Topping up AdBlue without it reaching your diesel tank Anywhere across Cornwall the light comes on, this is a routine for that day. - Pull in somewhere level, engine off, with time to spare — not hurried on the side of West Week Close. - Locate the AdBlue filler, read the cap, and speak the name "AdBlue" out loud while unscrewing it. It seems silly. It does the trick. - If both sit under one flap, check the diesel cap is still closed before you lift the bottle — and leave it on. - Using the bottle's own spout, tip slowly — and stop when it is full or the bottle is empty. - Only then, start the car: close the cap, check once more, and make sure the diesel cap was never opened. If at stage two or three you find you have already poured into your diesel side, stop there. Never go on to stage five. ## Put AdBlue in your diesel tank around Week St Mary already? Then the order of things is short. Don't start your engine. Keep your ignition off as well, since on many diesels switching it on alone runs the pump. Filling up with diesel won't weaken it: rather than mixing, AdBlue drops to the bottom of that tank, just where the fuel is taken from. Ask the staff to help push the vehicle clear of the petrol pump if you are at a forecourt — the Gulf, the another forecourt nearby or somewhere else. Your own drive around Week St Mary is where it stays. Stop as soon as it is safe then switch off, if your motor has already run. On the M5, under 50 miles from Week St Mary, that means the next exit. Tell us about how far it went: a run towards Plymouth, under 50 miles away, is a bigger job than a short hop across Week St Mary. ## Our arrival around Week St Mary, and what occurs next The van reaches your car anywhere it stopped — your own drive, near St Mary the Virgin, or by Whitstone Primary School. Which liquid went in, the quantity, and whether it ran: our engineers ask since the replies decide the work and price. The price comes on the call, ahead of any van leaving. Then the tank is emptied and the fuel system purged thoroughly. AdBlue crystallises and is corrosive to some of the metals in a fuel system, so it does not wash out on its own — which is why the flush matters more here than with petrol. The filter flushed or, if needed, replaced; clean diesel in; and then a test of the car. Before we leave, we start it and make sure that it is running correctly. With pumps safe on a busy forecourt and quiet enough to use outside a house at night, most jobs in which your motor has not run need roughly half an hour once our engineers arrive. Your insurer will ask for the engineer's report and your VAT invoice, and both are yours once the job is done. Payment is on the day, with no deposit. Plenty of insurance policies include misfuelling cover, and so it is worth checking yours whilst we're on the way. ## About Week St Mary itself Week St Mary is a rural village in inland Cornwall, situated approximately 146 metres above sea level. Week St Mary lies near several small settlements, including Week Green, Whitstone, and Bakesdown, and is about 30 miles from Plymouth. Week St Mary has a population of around 722 people, predominantly living in detached houses. Week St Mary is located in the South West region of England, about 197 miles west of London. ## AdBlue drains around Week St Mary and across Cornwall Being a rural village, Week St Mary has the same vans as nearby areas — Whitstone, Bakesdown — right through EX postcodes and the wider area beyond. A postcode starting EX22 6 gets the van to you fastest. Your car remains where it is. Anywhere it sits — near Ashbury hill fort, on a layby en route to Little Wood, on a drive — that is where it gets cleared. If you are close to a border, or somewhere hard to explain like the back of Penhallam Manor, ring and ask instead of assuming. ## In short, for Week St Mary people Read the cap before you tip. Petrol in Diesel drains it where it stands, anywhere around Cornwall, if AdBlue has gone in the diesel tank anyway — and so leave the car off then call 0333 366 0103.