Filter Guides & Resources

Nearly every filter carries a number, and that number is the fastest route to the correct replacement. On a spin-on filter it is usually printed around the canister body. On a cartridge or panel element it is printed on the end cap or stamped into the frame.

That number belongs to whoever made the filter, which is not always whoever made the machine. A genset built by one company may leave the factory with a filter branded by another. Both numbers are useful. Send whichever you can read.

When the number has worn off

Old elements spend their life in oil, heat and dust, and printing does not always survive that. If there is nothing legible left, the following will usually get you to the right part:

• The machine. Make, model and engine. On a generator, the engine make matters more than the alternator.
• A clear photograph of the old element from the side and from both ends.
• Dimensions. For a spin-on: outer diameter, overall height, and the thread size in the centre. For a cartridge: outer diameter, inner diameter and height.
• The gasket. Whether there is one rubber seal or several, and roughly how thick.

Send any of this on WhatsApp and we will come back with the equivalent from our range, the price and whether it is on the shelf.

Send us a part number

Four jobs, four different failure modes. The table below is the short version; the sections that follow go deeper on the ones that cause the most expensive damage when they are neglected.

A word about micron ratings

A micron rating on its own tells you less than it appears to, because a nominal and an absolute rating at the same number describe very different filters. What matters in practice is that the element meets the specification the equipment maker set and holds enough dirt to last the interval.

Understanding micron ratings covers this properly: nominal against absolute, how beta ratios convert to efficiency, a particle size chart, and why 5 micron is not automatically better than 10.

For the full side-by-side treatment of the three filter types, see air filter vs oil filter vs fuel filter.

Counterfeit filters are a real problem in every market where genuine parts carry a premium, and a fake filter is worse than no filter in one specific way: it gives you the confidence of having serviced the machine while delivering little of the protection. Most can be identified before fitting.

Seven checks before it goes on the engine

1. Printing and packaging. Genuine cartons use sharp, properly registered printing. Blurred text, uneven colour, bad spacing and misspelled words are the most reliable single giveaway.
2. Weight in the hand. A genuine filter contains more media, a heavier base plate and a proper spring. Copies feel noticeably light.
3. The pleats. Look into the element. Genuine media is evenly spaced with a consistent pleat count. Copies have fewer pleats, uneven gaps and sometimes visible glue runs.
4. The anti-drainback valve. On a spin-on oil filter, this should be nitrile rubber, flexible and resilient. A stiff, thin plastic flap is a strong sign of a copy, and it is the part that fails first on a cold start.
5. The gasket. It should be seated squarely in its groove, even in thickness, and springy rather than hard.
6. Thread and base plate. Threads should be clean and cut square. Rough, burred or visibly off-centre threads mean poor tooling.
7. The price. A price far below the market is not a bargain anyone is passing to you out of goodwill. It is the clearest warning of the seven.

Straightforward work, with two mistakes common enough to be worth naming before the steps: stacking two gaskets, and over-tightening with a wrench.

See also: choosing the correct air filter, air filter troubleshooting and the filter media guide.

Air filtration is where Pakistani operating conditions are hardest on equipment. Construction sites, quarries, unpaved routes and open plant yards load an element far faster than the interval in a manual written for milder conditions.

Do not clean a paper element with an air line

This is worth stating plainly because it is done so often. Blowing a paper element out with compressed air tears the fibres, and the holes it opens are too small to see and large enough to pass the grit that destroys cylinder bores. Tapping the element on the ground distorts the pleats and cracks the seal. Both methods leave the engine less protected than it was before, while looking like maintenance.

Washable and oiled-gauze filters are a different product with their own cleaning kits, and those instructions should be followed exactly. A standard paper element is a consumable: when it is loaded, it is finished.

Judge by restriction, not by the calendar

Many heavy-duty air cleaners have a restriction indicator fitted, and where one is present it is a better guide than hours run. The element is doing its job right up until the restriction reaches the limit; changing early wastes money, and changing late starves the engine of air, costs fuel and eventually lets dust through.

Do not forget the safety element

Many heavy-duty air cleaners hold a second, inner element. Its job is to protect the engine during the moment the main element is removed, and if dust gets past the primary. It is changed less often than the primary element, but it is not permanent. Check what your manual says and do not leave it in place indefinitely.

Diesel injection equipment works at very high pressure with extremely fine clearances, and it is lubricated by the fuel passing through it. That single fact explains why water in diesel is so damaging: water displaces the lubricating film, which causes rapid wear, and it corrodes the surfaces it sits against.

Where the water comes from

Rarely from one dramatic source. Usually it is condensation in a part-full tank as temperatures swing between day and night, water carried in during storage and transfer, or moisture absorbed by the fuel itself. Tanks left part-full over a long standby period are the most common case on generator installations.

Primary and secondary filtration

Most diesel systems use two stages. A primary filter, often combined with a water separator and a clear drain bowl, takes out the coarse contamination and free water. A secondary, finer filter then protects the injection equipment itself. Both matter, and fitting only one of them because it was the one in stock is a false economy.

Drain the bowl, and look at what comes out

A water separator only helps if it is drained. Make it part of the daily or weekly check, and pay attention to what comes out — it is one of the few direct indications of your fuel supply quality that costs nothing to read. Consistent water or sediment is telling you about the fuel, the storage tank, or both.

In a rotary screw compressor, oil is injected into the air end to seal, cool and lubricate. That oil must then be taken back out of the compressed air before it reaches the air line, which is the separator element's job. It is one of the few filtration elements whose condition you can read directly from a gauge, through the pressure difference across it.

Two things are worth knowing before anything else. Separator life depends far more on oil condition and intake air quality than on the element itself, so replacing one without changing the oil and air filters wastes it. And when oil appears downstream, the element is usually not the first thing to check — oil level, the scavenge line and the minimum pressure valve come first.

Both topics have their own guides:

• Why compressor separators fail — oil carryover, clogging, moisture and excessive differential pressure, with what to check in which order.
• Separator buying guide — OEM against aftermarket, how carryover efficiency is quoted, pressure loss and what decides lifespan.
• Compressor maintenance schedule — 250, 500, 1000 and 2000 hour checkpoints.

To read your own gauge, the separator life check turns a differential pressure reading into a percentage of life used, and the energy cost calculator puts a rupee figure on what a loaded element is costing you.

Start with the interval in your equipment manual. That figure assumes reasonable operating conditions, and it is the manufacturer's own recommendation for their machine. Then adjust it for the conditions you actually run in.

Conditions that shorten filter life

• Dust. Construction, quarrying, unpaved routes and open yards load air filters far faster than highway or indoor running.
• Heat and sustained load. Both degrade oil faster, which in turn loads the oil filter faster.
• Stop-start and idling. Long idling produces more soot per hour of useful work than steady running under load.
• Fuel quality and storage. Fuel drawn from site tanks or drums carries more water and sediment than fuel from a well-maintained supply.
• Standby duty. A generator that runs rarely is not necessarily under light duty. Condensation in a part-full tank and oil sitting unused both have their own effects, and many standby sets are serviced on a calendar rather than on hours.

Let the machine tell you

Where the equipment has them, use the indicators it gives you: an air restriction gauge, a separator differential pressure reading, oil analysis if you run a large or critical fleet. These are measurements of the actual condition rather than estimates, and across a fleet they usually pay for themselves.