At a recent car show I was asked about my air filter, more specifically how it looks clean and where did I get it from. Originally I had a single use white paper filters that were 1 1/2″ tall compared to the S&B (a K&N clone) which is 2 1/2″ tall which I now have. So I thought I would give a walkthrough step by step guide on how I clean and look after my air filter.

My old style disposable filter on the left (white) and my S&B on the right (red).

I purchased my S&B filter from Mustang Maniac here. The taller height allows a higher air flow for better performance and smoother engine response. Due to the unusual size not many manufacturers make them, secondly being a large size it can be expensive, depending on the make and of course the quality the filter.

Just a quick note about the engine’s air filter as it’s probably the most easily overlooked and simplest part of the car’s service, yet it’s a critical component for a number of reasons:

1. Prevents Engine Damage: The primary role is to trap dust, dirt, and other debris from the air before it enters the engine. Even small particles can cause significant wear and tear on engine components, potentially leading to costly repairs.
2. Enhances Fuel Efficiency: A clean air filter allows for optimal airflow to the engine, which is essential for efficient combustion. When the air filter is clogged, it restricts airflow, causing the engine to work harder and consume more fuel. Regular replacement can improve fuel efficiency by up to 10-14%. With modern engines the electronics can cope with rich mixtures better – to a point. Not such the case for a set fuel flow of a carburettor. The dirtier the filter the richer the mixtures becomes causing running issues.
3. Improves Engine Performance: A clean air filter contributes to better throttle response and overall engine performance. It ensures that the engine receives the right air-fuel mixture. more miles to the gallon of fuel.
4. Reduces Emissions: A properly functioning air filter helps maintain the correct air-fuel mixture, which is essential for the vehicle’s emission control systems. A clogged filter can lead to increased emissions and may trigger warning lights on the dashboard, not the case on our old classics. We just ‘feel’ the car and know it’s not right.
5. Cost-Effective Maintenance: Replacing an engine air filter is a relatively inexpensive maintenance task that can prevent more significant issues down the line.

Whichever style of air filter you use there are pros and cons for each type of filter:

Reusable Air Filters

• Long‑term savings – You buy once and reuse for years, reducing replacement costs.
• Lower waste output – Cleaning instead of discarding cuts down on landfill impact.
• Regular maintenance required – Must be washed and dried properly to maintain airflow and performance.
• Slightly lower filtration efficiency – Some reusable filters don’t trap ultra‑fine particles as effectively as paper options.

Paper (disposable or single use) Air Filters

• High filtration efficiency – Excellent at capturing fine dust and debris straight out of the box.
• Zero maintenance – Simply replace when dirty; no cleaning or drying needed.
• Higher long‑term cost – Frequent replacements add up over months and years.
• More waste generated – Single‑use design increases environmental footprint.

Then there is the look you want to go for (if you can see it), the crimson red or white or yellow. K&N have a good reputation and proven performance gains, even if it’s a slight horsepower gain. Some even use their K&N filters as bragging rights for their engines.

The original cost of my air filter was a little over £100 at the time. But, it has now gone up over the last few years due to the stupid costs of import charges and raw costs of materials. The equivalent replaceable filter which isn’t as tall in size as mine (2 1/4″ vs 1 3/4″) , is now £55. I would only need to replace the paper style a couple of times and it would be cheaper in the long run for the reusable style.

The downside to the reusable style is the regular cleaning yearly or 25,000 miles depending on climate (dusty) conditions and miles driven. To clean this style of filter there is a simple and easy to use kit which provides a cleaning solution and the replacement oil for the filter element pleats. The cost is a reasonable at around £15 for the aerosol kit.

This is what the kit looks like that i use. This is the Aerosol version instead of the squeeze oil version, which is slightly cheaper:

Inside is a instruction leaflet which can be downloaded here and two bottles, one an aerosol ‘Air Filter Oil’, the other a pump spray cleaner ‘Power Kleen’.

The principle is the same for what ever shape your air filter is, mine is oval and fairly long. Remove the air filter and tap out any loose debris from the elements, away from the engine.

Shake the cleaning bottle and pump the spray’s contents liberally onto the inner and outer elements of the filter to give it a good soak. I use a rubber (Wellington) boot storage tray which is perfect for the job. The tray has ridges that keeps the filter slightly raised.

The pump spray was good and directional, however the top of the screw cap leaked and ran down the bottle and over my hand. Not a huge amount, but annoying all the same. Perhaps I got unlucky with the bottle.

Leave the cleaner to work for ten minutes.

To remove all traces of the cleaner from the filter take the filter to low pressure water outlet and run the water both outside and inside to wash the debris out of the filter. I used a garden hose with a gentle directional jet by a drain.

The red oil was washed away pretty quickly, leaving the naked white cotton pleats underneath.

Flushing from the inside out was the majority of my cleaning which loosened the debris which can be seen running out from the pleats.

Keep running the water until all traces of the cleaner are gone. Below right you can see the cleaner being washed away to the side.

The filter is now clean and needs to be left to air dry naturally for an hour, or however long it takes to dry.

Once dry I was back to the tray to apply the aerosol oil to the pleats. Shake the spray can and apply the spray until an even coverage is achieved.

The fully sprayed filter should be left for at least twenty minutes where the oil will soak down the filter’s pleats and can be seen from the inside of the filter.

The aerosol was even and easy to apply, but a little messy on the nozzle.

Once the filter has been left to dry for twenty minutes and the oil has penetrated all the way down the pleated fabric it can be placed back in the car.

Optional: One final step before fitting that I tend to do is to spray a small amount of Gibbs Brand Lubricant onto a clean cloth to make it damp, then very lightly wipe the cloth onto the inside mesh of the filter to give it some extra protection. You don’t want anything else on the pleats other than the K&N oil. The wipe over was a seriously light brush to add a thin film and that’s all. You don’t need to do this step, but I like to do it.

Once refitted the filter looks really good and was left overnight. The next day the car fired up nicely and seemed to idle a little smoother, psychological improvement? No, it did run smoother and the process is well worth it.

How long, well not long but most of the process was waiting. The total minutes actually doing the cleaning was around thirty minutes. Total time for the whole procedure was about two and half hours including the waiting.

That’s it, a pretty simple process, but it does make a difference on these older mechanical engines which rely on a good balance of fuel and air. If your car starts to run a bit erratic, check the air filter for a quick fix.