Filters replacement interval

**B92 8NW** · 21st September 2006, 08:28 PM

I noticed at the last service my mechanic did not replace the air or fuel filter. He said that the fuel filter and air filter are good for 20k... I beg to differ.

So is the correct interval 10k or 20k

? For what they're worth, I'd say 10k[?]

**DEFENDERZOOK** · 21st September 2006, 08:39 PM

with the fuel filter...you can never tell by looking at it......
on a normal road car.....as a rule....you change the fuel filter every time the air filter is changed.......

the air filter can easily be seen......just remove it and check it to see how clogged up it is........
if its too clogged with gunk......replace it.....

on a 4wd however.....the air filter will clog up more often due to dusty conditions........
a bit of a tap against something hard (brick wall) or a blow out with an air hose will usually
clean it enough to keep going......but if the dust starts coming through it you should replace it.....

since this will happen more often if you are off roading alot....there is no need to change your fuel filter each time.....
so the 20,000km interval for the fuel filter is ok....there is no harm in changing at 10,000 or 15,000kms.....
just depends on what you can afford......

**ladas** · 21st September 2006, 08:44 PM

Originally Posted by joel_nicholson

I noticed at the last service my mechanic did not replace the air or fuel filter. He said that the fuel filter and air filter are good for 20k... I beg to differ.

So is the correct interval 10k or 20k

? For what they're worth, I'd say 10k[?]

I can only answer for Disco 1 and 11,

According to the owners manuals the air filter should be replaced after 40,000 k or 24 months.

Fuel filter 80,000 k

I'll do a double check on rave and let you know

**B92 8NW** · 21st September 2006, 08:47 PM

Originally Posted by ladas

I can only answer for Disco 1 and 11,

According to the owners manuals the air filter should be replaced after 40,000 k or 24 months.

Fuel filter 80,000 k

I'll do a double check on rave and let you know

Hmm funny you mention it because my owners manual and workshop manual conflict... owners says air and fuel 40k and workshop says 20k. 80,000k seems an eternity to use a fuel filter...

**DEFENDERZOOK** · 21st September 2006, 08:58 PM

normally......not going by any workshop manuals or handbooks......
fuel filters should be changed every 2 years or 40,000kms.......

air filters when they are dirty.........they are easy to check and the dirt can be seen.....
you cant check your fuel filters that easy........

but if you really want to work out when to change them.....
remove the fuel cap to release any pressure in the tank.....then remove the fuel filter
without losing too much fuel out of it.....
no give the fuel filter a bit of a shake and then tip out the fuel thats still in it into a clean glass jar......
but you must drain the fuel out from the INLET side of the fuel filter.....
now check to see how dirty the stuff you have in the jar is......

if you want to check what the filter is actually doing.....tip some fuel out of the OUTLET side into
another clean glass jar and compare the difference......this jar should have clean fuel.....

this a simple test you can do at home....if the fuel out both ends is clean....
there is no need to change it yet.....but dont leave it forever.....

even if its clean sfter 2 years or 40,000kms.....change it anyway.....
you dont want the filter element to break down and allow everything through
to the injectors......

**ladas** · 21st September 2006, 09:05 PM

I think Zook has it spot on

If the air filter is servicable and not letting any cr*p through then a good clean will suffice up to however many K's

Fuel filter - maximum 40k in my mind

**rick130** · 22nd September 2006, 05:59 AM

fella's, this has been discussed before. Remember that there is a downside to changing an air filter too frequently, it lets increased contaminents into the engine. A filters efficiency increases with dust loading, all the way up to the point that the increased pressure drop through the media starts to degrade performance. This is the reason large off road equipment uses a simple pressure drop indicator, usually a red button on the air cleaner that indicates when to change the filter.
There have been some excellent posts by Isuzurover on this subject. He is a filtration engineer.

Maybe I can shed some light on the filter changing issue.

Contrary to popular belief, most filters do not work like sieves, air filters not at all, and oil/fuel filters only slightly. Conventional filters capture particles by inertial impaction, interception, and diffusion (brownian motion) - although the latter plays almost no role in oil/fuel filters.

As a filter traps particles, those collected particles assist in filtering further particles from the air stream, so filters will become MORE EFFICIENT (at capturing particles) the more particles they collect. There is a corresponding increase in pressure drop, however this is always linear, whereas efficiency increases are initially more logarithmic (increase very rapid at first).

So for air filters, the best thing you can do for engine longevity is to leave the filter changes as long as possible, and only change the filter when pressure drop becomes too high. 110 countys with 3.9L ISUZU engines have a large twin element donaldson filter, with a big sticker "do not service (change) element to frequently" and "change element only when pressure drop reaches set level". So not only are you wasting money, you are actually harming your engine by changing the AIR filter too frequently.

from here http://www.aulro.com/afvb/showthread...hlight=filters

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