Knowledge Hub
13/11/24
If you own a Land Rover or Range Rover, you may have seen a message on your dashboard instructing you to "Top Up DEF" or something similar. If you’re unfamiliar with DEF (Diesel Exhaust Fluid), you might be wondering what it is, why your vehicle needs it, and how to go about refilling it properly. In this guide, we'll cover everything you need to know about DEF and why it's important not to overfill it.
Diesel Exhaust Fluid, also known as ADBLUE, is a non-toxic, colourless liquid made up of 32.5% urea and 67.5% deionized water. DEF is used in vehicles equipped with Selective Catalytic Reduction (SCR) systems to reduce harmful nitrogen oxide (NOx) emissions from diesel engines. When injected into the exhaust stream, DEF helps break down NOx gases into harmless nitrogen and water vapor, making your vehicle more environmentally friendly and compliant with emissions regulations.
Your Land Rover or Range Rover has a dedicated DEF tank, and when the fluid level gets low, your vehicle will alert you to top it up. If you ignore the warning and let the DEF level drop too low, your vehicle may enter a restricted performance mode or even refuse to start until the DEF has been replenished.
Before adding DEF, ensure that the message on your dashboard is asking you to "Top Up DEF." Sometimes, owners confuse this with a different message stating, "DEF Quality is Poor." If you see this message, it means the fluid is either contaminated or of very poor quality and simply topping it up will not resolve the issue. In such cases, you may need to drain the DEF tank and refill it with high-quality DEF that meets ISO 22241 standards. (This work would have to be carried out by professionals, and the system would need to be reset.)
Topping up DEF is a straightforward process. Here’s how to do it:
Many Land Rover and Range Rover owners have heard that they shouldn't completely fill the DEF tank, but why is this the case?
Keeping an eye on your DEF levels is essential to maintaining your Land Rover or Range Rover’s performance and emissions compliance. When you see the "Top Up DEF" warning, make sure to refill with high-quality DEF, follow the correct procedures, and avoid overfilling the tank. Also, double-check that the message is actually a "Top Up DEF" warning and not a "DEF Quality is Poor" alert, which indicates a different issue requiring a workshop visit to investigate the issue. By doing so, you’ll ensure your vehicle runs smoothly and efficiently while helping to protect the environment.
If you’re not sure about any of this and would rather it was checked for you, please call Newbury 4x4 Centre on 01635 32028