This nifty little button you've probably never noticed can save drivers up to £100 and lead to healthier car journeys. Auto sage and popular YouTube mechanic Scotty Kilmer said he's lost count of how many times customers have brought their car in saying the air conditioning doesn't work when the only thing wrong was a clogged filter.

The prolific poster said clogged filters meant less airflow and a harder time getting your vehicle to cool down. In a popular video, Scott shows drivers how to short-circut this very common problem by accessing the cabin are filter.

Scotty explains: "Today I'm going to tell you about the hidden air filter fitted in your car that nobody knows about. It's called the cabin air filter. You squeeze the glove box and it comes out.

"If you look inside there’s a cover that snaps off and out comes the cabin air filter. This filters the air that goes into your air conditioning and heating system."

Also known as the pollen filter, cabin filters are built into modern cars and help regulate the air in your car's air conditioner and heating system.

Replacing them can prove especially handy for drivers or passengers with allergies and working filters are said to help stop coughing and sneezing. Without them, drivers risk experiencing much less power and more musty odours. They can also experience a whistling noise from their airvents.

Scotty also said they can be cleaned by removing the filter and whacking it against a wall or the ground to get the dirt out. If it's real dirty, you'll need a replacement. 

The mechanic, who has been fixing cars for 57 years, said: "My advice is buy it online cheaper because the auto parts store charges too much. And if you're really sensitive to smells like my wife, you can buy a black carbon-activated one like this that works better."

Carbon activated filters tend to be more expensive than standard purifiers but they are said to be more affective at blocking pollutants like soot, dust and diesel fumes. Carbon activated filters are especially useful for motorists spend a lot of their time in bumper to bumper traffic as they tend to block out more fumes.

These filters need replacing more frequently with manufacturers recommending drivers swap them out evey 15,000 miles. According to Google, the cost of replacing a car's pollen filter can range from £40 and £100. An air fitler typically costs around £8 and £26 whole a mechanic's labor can cost anywhere between £30 and £70, according to Fixter.