Just checked my air filters. The filter box was full of dead flies. The filters themselves did not seem too bad just a little discoloured. How do you really know when it's time to change them
Good questions. I think they are just replaced in due course rather than being 'dirty'. I bet in other countries they have more reason to need to be changed - ie dusty climate. Chris
Moons ago I had a Renault Laguna II, which had been my company car from new. I had left the firm, but returned shortly afterwards. In between the car had been crashed. When it returned to me it also needed a service. After this fuel consumption was down by 5 mpg... Noticeable. Took the dealer 3 trips to spot an air filter full of 'cellulose'. Not sure why it had not been changed at the service in any case. A dirty fuel filter is going to use more fuel, or I imagine potentially 'strangle' an engine.
I've just replaced the air and cabin filter in my car. I think there's little argument mine needed doing.
A unit like this is used to monitor air filter efficiency on commercial vehicles; ebay item 200622486388 Mercedes trucks used to have an indicator on the dashboard where a sensitive differentiual pressure gauge would reveal a red flag as the filter blocked. It probably wouldn't be too difficult to obtain one and use it - you could argue it would be a better use of dashboard space than the gimmicks usually found there.
Some Land Rover Defender diesels had a visual gauge in the engine bay (on the air filter canister) in the 1990's Tdi 200 models.
