When is an air filter 'Dirty'

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GlenQ

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Joined
Jun 16, 2011
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202
Location
Derbyshire UK
Car
2004 W220 S320 CDI
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:confused:
 
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.

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The colour isn't a good indicator of blockage, really you need a manometer.
 
Not always practical on a domestic vehicle though ?!
 
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.
 
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.
 
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.

As do some Mercedes cars.
 

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