--- title: AdBlue in a Diesel Tank Blaenllechau: Explained canonical: https://www.petrolinadieselcar.co.uk/adblue-in-diesel/blaenllechau-rhondda-cynon-taf/ location: Blaenllechau county: Rhondda Cynon Taf latitude: 51.666720 longitude: -3.446250 service: AdBlue in a Diesel Tank updated: 2026-10-17 --- # Avoiding AdBlue in a Diesel Tank in Blaenllechau: Why It Occurs Pause reading a minute when your diesel tank already has AdBlue in it: ignition off, engine off, and ring 0333 366 0103. Normally, when your motor has not run, it is drained and thoroughly flushed where the car is around Blaenllechau. The remainder of this page explains why it occurs and how to ensure it does not — useful if you're reading ahead of time. ## AdBlue in a diesel motor: two tanks, two fillers Plenty of current diesels on the roads around Blaenllechau and Penrhys carry two liquids, not one. Diesel goes to your motor. Kept in a tank of its own, AdBlue is sprayed into the exhaust stream to clean it. Each tank has its own filler. Some motors keep the AdBlue filler in your boot or under the bonnet; a lot of others have the two side by side behind one flap. The diesel side is fuelled at the petrol pump all the time. Someone who has to stop and think where it goes normally tops up the AdBlue side, from a bottle, and much less often. The mistake grows in the gap between them. ## How does AdBlue in your diesel tank take place in Blaenllechau? Rarely is it carelessness: normally three things coincide. First, the warning. Low AdBlue brings a message from your car, and letting it run out leads to limp mode — so a rushed top-up, perhaps before work off Commercial Street, perhaps at the pub in the village on the way home after work. The old car's cap is where the hand goes — but a hire car, a new motor or a company car puts the fillers somewhere else. That's the second factor: an unfamiliar motor. And the bottle fits. A bottle with a spout goes into a diesel filler as easily as an AdBlue one, so nothing stops the pour once it has started. It's seconds, whether in Ferndale or right in the centre of Blaenllechau. ## How to tell the AdBlue filler from the diesel one Whether a Blaenllechau forecourt or a drive over in Ystrad, spend a couple of seconds over these before anything goes in. - Position can mislead; the cap does not. AdBlue caps are often blue or carry the word "AdBlue" — diesel ones usually do not. - On plenty of motors, size gives it away: AdBlue gets the smaller filler neck. - Check inside your fuel flap: plenty of cars carry a label there showing which fuel goes where. - The handbook. If the filler is not by the diesel cap, it's in your boot or under the bonnet, and the handbook says which. - The person who drove the car last. On a hire or company car picked up from somewhere like the car park outside Ystrad Rhondda, ask before you leave, not when the light comes on. ## Topping up AdBlue without it reaching the diesel tank Anywhere across Rhondda Cynon Taf the light comes on, here is a routine for the day. - Not in a rush on the side of Albert Street, not on a slope, not with the engine running: park then switch off properly. - Locate the AdBlue filler, check the cap, and say the word "AdBlue" out loud as unscrewing it. It seems daft. It works. - Leave your 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, tip slowly — and stop when it is full or the bottle is empty. - Close the cap and check once more. Make sure the diesel cap was never opened. Only then start your car. Stop there if you find, at step two or three, that you have already poured into your diesel side. Never go on to step five. ## AdBlue in the diesel tank already, in Blaenllechau? Short list, then. First: the motor remains off. Do not switch your ignition on; on plenty of diesels that alone runs the fuel pump. Filling up with diesel won't weaken it: instead, AdBlue sinks to the bottom of the tank, just where the fuel is drawn from. If you are at a forecourt, whether it's the Murco or the Texaco, ask the staff to help push your car away from the pump. Your own driveway around Blaenllechau is where it should stay. If your motor has already run, stop as soon as it is safe then switch off. Blaenllechau lies under 15 miles from the M4; there, use the first exit. Roughly how far did it go? Hopping across Blaenllechau is less work than a trip of under 25 miles towards Cardiff, so tell us. ## When we get there around Blaenllechau, what occurs? Our van comes to the car anywhere it stopped — your own drive, near Ferndale Library, or outside the local primary school. Those answers decide the work and our quote, so our engineers ask what got in, about how much, and if it's run. The quote is given over the phone, ahead of any van leaving. Emptying that tank comes next, followed by a full flush of the system. With AdBlue that counts more than with petrol: it crystallises and is corrosive to some of the metals in a fuel system, so it does not wash out on its own. The filter cleaned or, if needed, replaced; clean diesel in; and then a check of your car. We don't go until it has been started and is running smoothly. Using pumps fine on a busy forecourt and quiet enough for use outside a house at night, most jobs where the engine hasn't run take about half an hour once we are there. Your insurer usually wants the engineer's report and the VAT invoice, and you get both once this job is done. Payment comes on the day, with no deposit. While we travel, have a look at your policy; many include cover for misfuelling. ## About Blaenllechau Blaenllechau is a suburban area situated lakeside in Rhondda Cynon Taf, with a mix of terraced housing and scenic views. Blaenllechau sits at an elevation of 251 metres, overlooking the surrounding landscape. Blaenllechau is located near Ferndale, Tylorstown, and Cwmaman, and is approximately 17 miles from Cardiff. Blaenllechau has a population of around 2288 residents. ## AdBlue drains in Blaenllechau and across Rhondda Cynon Taf Tylorstown and Cwmaman are among the towns around Blaenllechau, a residential suburb, that the same teams cover, over CF postcodes. The van reaches you fastest with a postcode starting CF43 4. Your car does not need to move. Our technicians drain it where it is — a side street near St Joseph's, a lay-by on the way to Blaenllechau Park, a drive. Guessing won't help behind Cwmaman Theatre, close to a border, or somewhere awkward to describe; phone and ask. ## The short version for Blaenllechau motorists Read the cap before you tip. Still AdBlue in your diesel tank? Petrol in Diesel can drain it wherever it is, anywhere across Rhondda Cynon Taf: switch it off and call 0333 366 0103.