How to pass MOT emissions test


You may be worried about passing your annual emissions inspection but in this article, you will learn how to prepare your car to pass the yearly inspection.

It’s a safety test that should be carried out every year, which means that you’re checking your car to make sure it’s legally safe to drive on UK roads. You will also need to check your tires are in good condition, brakes, and headlights to make sure they work properly. There are preventive measures that you can make so that your vehicle passes the emissions inspection. In MOTs for older cars, they use a dynamo-metre test to measure how much gas comes out of the tailpipe so you’ll need to make that the tailpipe gases are low and less pollutant. Here are parts of the car that you need to check:

Engine Oil

If you want to make sure that your car is in good condition, you should change the oil and filter before you have your car inspected. If it gets dirty during the inspection, then changing and filtering will ensure that no harmful vapours are sucked into and burned by the PCV system. And you’ll want to have clean oil, so right before an inspection is when it’s the best time to get it done!

Sparks Plugs

Make sure you have the right spark plugs installed in your car because they are responsible for creating electricity. If a spark plug is worn down or has too big of a gap then your emissions will be high and you may fail the emission test if it’s not replaced.

Cooling System

You would want to check the cooling system for your car. If it’s low, the engine will get hot and pollute more as time goes on. You should realize that the engine gauge doesn’t have to be overheating for the engine to still be running very hot. Check to make sure the coolant is full and clean; also turn up your AC unit so it can suck in more air. The test takes place when cars are stationary so make sure fans are spinning at their max capacity. If the cooling fans are not sucking sufficient air, the engine will run much hotter and your vehicle will fail the test.

Air Filter

The next best thing to do is make sure you have a clean air filter. If your car’s air filter isn’t in good shape, it could block the flow of fresh air, causing the engine to run lean and cause too much pollution. This also causes the engine to run hotter and the gases of the exhaust to get hotter which emits more NOx, which is a measured pollutant that can fail your test.

Engine Light

Modern cars don’t have to be tested on a dynamometer for safety and performance. They just plug into the computer, which can tell if there are any problems that need fixing. Cars from 1996 onwards are all inspected this way and so when your car has a check engine light on, you should fix it before you take it in for inspection. If the check engine lights on, it means there is a trouble code located in the computer and it will fail the test when inspected during your MOT. The number of codes in just one car can be overwhelming – there are over 2 000 different trouble codes!

Fuel Injection Cleaner

Using a quality fuel injector cleaner can improve the performance of your vehicle, and it will also have an effect on engine efficiency. It’s advised to pour the formula into the tank of your fuel injector cleaner before you fill up with fuel. This way, it mixes with the fuel more efficiently and in a far better capacity than if it was poured on top afterwards. However, if the car isn’t running well, it has a serious issue that needs to be sorted out. If you do this when your car is running okay, this might allow it to pass – because the solvent burns very clean so you’re cleaning out all systems as the clean gas comes out of the exhaust.


If you want to pass the emission test, it is important that your car has been checked out. Try reading something online and searching for YouTube videos on how to diagnose problems with your car before going to a mechanic – this will give you an idea of what might be wrong with the vehicle before taking it in. You can try your best to sort out any issues with the car before the mechanics inspect it.