--- title: St Cleer: AdBlue in a Diesel Tank, Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/st-cleer-cornwall/ location: St Cleer county: Cornwall latitude: 50.486710 longitude: -4.470610 service: AdBlue in a Diesel Tank updated: 2026-10-03 --- # Why It Occurs and How to Prevent It: AdBlue in a Diesel Tank in St Cleer Keep the engine and ignition off then ring 0333 366 0103 now — the rest can wait when AdBlue is already in your diesel tank. Around St Cleer, catching it before your motor runs usually leaves draining and a thorough flush where it stands. Reading in advance? In that case the rest explains why it happens and what to prevent it ever happening. ## Why does AdBlue in a diesel vehicle need its own filler? Diesel goes to your motor — but plenty of modern diesels driven about St Cleer and Higher Tremarcoombe hold a second fluid too. Stored in a tank of its own, AdBlue is sprayed into your exhaust stream and cleans it. Every tank has one filler of its own. On a lot of vehicles the two sit side by side under the same flap; on others the AdBlue filler is in the boot or under the bonnet. Diesel gets filled at each filling station visit, week in, week out. Someone who has to stop and work out where it goes normally tops up the AdBlue side, from a bottle, and much less commonly. The slip lives in that gap. ## How does AdBlue in the diesel tank take place around St Cleer? Carelessness rarely causes it. What does is three things coming up at once. First, the warning. Low AdBlue triggers a warning from the car, and running out leads to limp mode — hence a hurried top-up, perhaps before work off Well Lane, perhaps at Market Inn on the way home that evening. The old car's cap is where the hand goes — yet a hire car, a new vehicle or a company car keeps the fillers elsewhere. That is a second factor: a new vehicle. A spouted bottle finds no obstacle at a diesel filler no more than at an AdBlue one. So the tip, once begun, carries on. It's seconds, be it out in Tremar Coombe or bang in the heart of St Cleer. ## The AdBlue filler and your diesel filler: telling them apart A couple of seconds is all these take — so check them before you tip anything, on a drive in Lower Treworrick or a forecourt in St Cleer. - The cap. The AdBlue cap is often blue, or marked "AdBlue". The diesel cap normally isn't. Read it rather than going by position. - The size. On many cars the AdBlue filler neck is the smaller of the two. - The flap. Look inside the fuel flap for a label. Many cars say there which fuel goes where. - The handbook. If the filler is not by the diesel cap, it is in your 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 — if you collect a hire or company car from somewhere like the car park outside Liskeard. ## Topping up AdBlue without it reaching the diesel tank Anywhere in Cornwall the light comes on, this is a routine for the day. - Switch off once parked — flat ground, motor off, and never in a rush by Fore Street at the roadside. - Find the AdBlue filler and read the cap. Say "AdBlue" out loud as you unscrew it. It sounds daft and it does the trick. - Both behind one flap? So confirm the cap on the diesel side is still shut ahead of raising the bottle. - Pour slowly, using the bottle's own spout. Stop when it's full or when the bottle is empty. - Only then, start the vehicle: close the cap, check a second time, and make sure your diesel cap was never opened. Find at step two or three that it's already gone into the diesel side? So stop right there. Stage five stays out. ## St Cleer: already put AdBlue in the diesel tank? Do not start the engine: that's how the short order of things begins. Keep your ignition off as well, since on plenty of diesels it by itself runs your pump. AdBlue does not mix with diesel — it sinks to the bottom of the tank, where the fuel is sucked from — so don't top up with diesel to thin it. Ask the attendants to help roll the car away from the pump if you're on a forecourt — the BP, the Morrisons or somewhere else. If you are on your own driveway in St Cleer, leave it where it is. Stop as soon as it is safe then switch off, if your motor has already run. Leave the M5 — under 50 miles out of St Cleer — at the next junction. Roughly how far did it go? Crossing St Cleer is smaller work than a trip of under 25 miles to Plymouth, and so say. ## Our arrival in St Cleer, and what occurs next The van reaches the vehicle wherever it has come to rest — your own drive, near the centre, or outside St Cleer Primary Academy. Both the work and the quote depend on three replies — what liquid, which quantity, and if it's run — so our technicians ask. During the call itself, you hear the price — before dispatch. Then the tank is emptied and the fuel system flushed thoroughly. 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 the flush counts more here than with petrol. After the fuel filter is flushed — or renewed, if needed — fresh diesel goes in, and finally the vehicle gets tested. Next our engineers fire it up and make sure it runs smoothly before we go. Most jobs are done in roughly half an hour after our technicians arrive, provided the engine hasn't run — and the pumps our engineers use are safe on a busy forecourt and quiet after dark beside a house. The insurer will ask for an engineer's report and the VAT invoice, and you get both at the end. Payment is on the day, with no deposit. Many insurance policies include misfuelling cover, so it's worth checking yours while we are on the way. ## About St Cleer St Cleer is a rural village in Cornwall, situated inland at an elevation of 213 metres, with detached housing being the predominant type of accommodation. St Cleer lies near the villages of Tremar Coombe, Tremar, and Lower Tremar, and is approximately 16.6 miles from Plymouth. St Cleer has a population of around 1144 residents, and its location provides a quiet setting away from major urban areas. St Cleer is also relatively distant from London, at a distance of 201.5 miles. ## AdBlue drains around St Cleer and across Cornwall St Cleer is a rural village, and our teams that cover it also work the places near it, Tremar and Lower Tremar among them, across the PL postcode area. Quickest of all: give a PL14 5 postcode for our van. The vehicle remains put. Our engineers drain it where it is — a side street near St. Cleer's Well, a lay-by on the way to St Cleer Memorial Park, a drive. Ring and ask instead of assuming if you are close to a border, or somewhere hard to explain, like the back of St Cleer Village Hall. ## For St Cleer people, the short version Tip nothing till you have read the cap. If AdBlue has gone in your diesel tank regardless, leave the vehicle off and call 0333 366 0103. Petrol in Diesel drains it where it waits, anywhere in Cornwall.