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L3785



Member Since: 08 Oct 2024
Location: Yorkshire
Posts: 59

United Kingdom 
AdBlue
I apologise in advance for this stupid question but thought I’d use the collective expertise of this forum.

I noticed earlier that my Remote App shows “Refill 1.5 gallons” under Diesel Exhaust Fluid. I’m assuming that it means I should top-up with 5 litres.

If that’s the case, should I do this? If so, is it acceptable to mix new fluid with what was in the vehicle when I bought it?

Or, should I just wait and do a full change when I plan to book it for a full oil change at 10,000 miles (current mileage is 6,500)?


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 2025MY Defender 90 D250 X-Dynamic HSE | Santorini Black with Black Pack
Post #1073071 9th Aug 2025 10:07pm
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lightning



Member Since: 23 Apr 2009
Location: High Peak, Derbyshire
Posts: 3330

United Kingdom 
You can top it up if you want, but with 6,000 miles of range remaining it's not necessary.
lt's fine to use any Adblue and mix it with whatever is already in there.

What you don't want to do, is let it run out as the engine won't start once the Adblue is empty.

l believe you get a warning on the dashboard when it's down to 1,000 miles of range. Maybe top it up then.

Some have also reported issues if you overfill the Adblue tank, although l don't know why that would happen.


Last edited by lightning on 10th Aug 2025 10:58am. Edited 1 time in total
Post #1073073 10th Aug 2025 9:40am
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L3785



Member Since: 08 Oct 2024
Location: Yorkshire
Posts: 59

United Kingdom 
That’s really useful advice, thanks so much.

I’ll get it topped up at 10,000 miles with the oil change on that basis, cheers 👍🏼 2025MY Defender 90 D250 X-Dynamic HSE | Santorini Black with Black Pack
Post #1073074 10th Aug 2025 9:43am
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ruben



Member Since: 04 Feb 2021
Location: ASTURIAS
Posts: 362

Spain 
Hi, One more detail is missing! It's also not advisable to leave it or push it to very low levels. It seems to be necessary not to have too much air inside. If the tank is too empty, the oxygen encourages undesirable crystallization of the urea, which leaves residues in the tank, a potential source of problems with the AdBlue sensors and injectors. This is why the car sends such early warnings. What I do is put in 1 liter less than what the car asks for. When it needs a refill, it tells you the number of liters needed. So that's what I do, but subtract one to avoid overfilling. If it asks for 6 liters, I put in 5. bye!! Defender 110 SE I6 D250 23MY
ExDiscovery 3 TDV6 SE
Post #1073076 10th Aug 2025 9:59am
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Clemmo



Member Since: 03 Aug 2012
Location: Mile Oak
Posts: 1271

England 
The issue with overfilling is also due to crystalization of the Adblue.
At the top of the filler neck there is an air hole which is prone to blocking following an overfill.
The key is to not allow the Adblue to backwash..use the filler neck provided and get it pushed right down the tank. Put in less than you think you need.
It lasts very well anyway Thumbs Up
Post #1073077 10th Aug 2025 10:39am
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lightning



Member Since: 23 Apr 2009
Location: High Peak, Derbyshire
Posts: 3330

United Kingdom 
Do you think it's okay to leave it until the warning comes up at 1,000 miles range remaining?
Post #1073080 10th Aug 2025 10:59am
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ruben



Member Since: 04 Feb 2021
Location: ASTURIAS
Posts: 362

Spain 
I would say NO, not is a good idea! I try to fill it up when it asks me for the first time, minus a liter, so it's always between 60 and 90%. or so!! Defender 110 SE I6 D250 23MY
ExDiscovery 3 TDV6 SE
Post #1073081 10th Aug 2025 11:18am
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Clemmo



Member Since: 03 Aug 2012
Location: Mile Oak
Posts: 1271

England 
lightning wrote:
Do you think it's okay to leave it until the warning comes up at 1,000 miles range remaining?


Absolutely..this gives you plenty of time.
You really need to be filling with AdBlue the absolute minimum of times.
~So run to warning..get product..add within 500 miles..dont overfill..( no splash) Thumbs Up

Only use fresh Adblue. Do not store it past 6 months once opened. Store in cool dark space. Be wary where you buy it from...look how it is stored?
Many Forecourts have it stacked up outside in bright sunlight which rapidly degrades the product.
It has to be stored below 21degC.

https://www.fleetalliance.co.uk/blog/dos-donts-using-adblue/
Post #1073084 10th Aug 2025 12:15pm
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Fifth Horseman



Member Since: 08 Mar 2011
Location: Lanarkshire
Posts: 339

United Kingdom 2011 Defender 110 Puma 2.4 XS CSW Santorini Black
The AdBlu tank is 20L (about 4.4 gallons (UK)) so its still well over half-full.

Also there have been instances where overfilling has confused the level sensor leading the system to think the tank is still empty.

As most of the refi containers are 10L I'd wait until it says "Refill 2.5 gallons" and then chuck a whole 10L container in. Defender 110 D300 X-Dynamic HSE MY22
Defender 110 Station Wagon 2011 (gone)
Defender 110 DCPU 2007 (gone)
Post #1073101 10th Aug 2025 6:02pm
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ruben



Member Since: 04 Feb 2021
Location: ASTURIAS
Posts: 362

Spain 
Mine, so far, has only notified me of refills a couple of times, here we don't use gallons, but liters, and both times it always asked me for 6 liters of AdBlue at the first warning, given that around here you usually see 5-liter bottles, so it's perfect to obey the first message with a full bottle, which leaves you a margin of 1 liter that avoids the risk of overfilling, and it doesn't warn me again and that's it, so the same things in different worlds, nothing more! Defender 110 SE I6 D250 23MY
ExDiscovery 3 TDV6 SE
Post #1073103 10th Aug 2025 6:31pm
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