Oil Filter Analysis

New filters added 15/10/04

I've often wondered if the higher price charged by the dealer for a common item like an oil filter is actually money well spent. Or does it make sense just to get any make of filter from the local factors, because they're probably all made by the same company, and save yourself a few bob as well?

As I do regular oil and filter changes on my Honda 2.3l engine, I recently decided to get an aftermarket filter from my local factor at the same time as I got my oil. The first thing I noticed was the size, much smaller than the OE filter, so I decided to open up a genuine filter and compare it to the innards of the aftermarket filter. I then also purchased two more filters and compared those as well.

Now it's fair to say I'm not a filtration expert, but I am an Engineer. So I've cast an Engineers' eye over things like the quality of the components, filtration area etc. As far as the actual filtration medium itself, unfortunately I don't have the equipment to measure things like particle size and pressure drop, so I've assumed that the more material there is, the better. And the thicker the material, the better. Don't forget, these are only my personal views and observations.

What's in a filter?

The really important parts are the filter material itself, the anti-drainback valve and the bypass valve. The quality of the anti-drain valve is important, as it is this that retains the oil in the filter canister and saves it having to be filled every time the engine is started, reducing engine wear. The bypass valve is used to allow oil to bypass the filter element should it become blocked, or the flow rate becomes too great due to high oil viscosity (from cold starts) and/or high flow rates at high engine speeds. It is therefore important that it only allows oil to bypass when required and not during normal operation. The best material for the valves is silicone rubber as it has better thermal stability. Nitrile should be ok, but at low temperatures it gets quite stiff, and at higher temperatures can become very pliable. Metal on metal is not good for seals, as it simply doesn't seal very well. Here's an exploded view of a typical filter:-

CHAMPION

The Champion filter is reasonably priced (£6.99 from Halfords) and has the second highest filter area. The canister is reasonably thick and had a good quality crimp joining it to the end plate. The filter material appeared a little thin. A big negative though is that the anti-drain seal that sits against the  end plate didn't seal very well, as the sealing surface isn't flat due to spot welds on the end plate. Basically, the spot welds have created depressions on the rear of the end plate, and it is against these that the seal rests. Another problem is the main filter seal is only a slight interference fit in it's groove, with the possibility that it could be displaced when positioning the filter, prior to screwing it on, especially if it's a tight location. Seals were all moulded nitrile.

HALFORDS

The Halfords filter is reasonably priced (£6.29) but has the second lowest filter area. The filter material itself is also pretty thin, as is the canister metal, and the main crimp looked a little lightweight. The anti-drain valve is a different arrangement to the other three, in that it's a floppy nitrile disc held in place by a spring disc. It appears to offer a good sealing arrangement against the end plate. The bypass seal is nitrile rubber and is mounted in a spring steel plate (top left). The downside as I saw it, is the plate with bypass valve, and the end plate with the anti-drain valve, are sealed only against the ends of the filter element, which are cardboard. The glue joining the filter element to the cardboard endplates didn't inspire much confidence, as it came apart easily. The main seal is only a very slight interference fit in it's groove, and could easily fall out or get misplaced when fitting.

BLUEPRINT

The Blueprint filter is a  low price (£5.61) and are available from many motor factors. Canister and end plate construction was good, and the main seal is crimped to the endplate so couldn't be displaced when fitting the filter. The anti-drain valve is moulded nitrile, and after a spell in the fridge was pretty stiff. The low points however, were the lowest filter area of the group (so far), and the bypass valve that was metal against metal. As I could see light through the bypass valve when closed, I can only assume that it would let some dirty oil bypass the filter at all times, as well as allowing the dirty oil that should be retained in the canister when shutting down the engine to bleed through, thereby negating the effect of the anti-drain valve. Filter material looked and felt pretty thick though.

HONDA GENUINE

The genuine Honda filter is the most expensive at £11.39, and also nearly the largest. One big difference is the filter element itself, as it had both horizontal and diagonal pleats. This has allowed more filter area in the canister, and the filter material felt good and thick. The anti-drain valve is moulded silicone rubber that retained it's characteristics at extremes of temperature. The bypass valve is also of good design, as it is a metal valve with a nitrile seal. The canister is pretty thick, the crimp to the end plate is substantial, and the main seal is crimped in place so can't get displaced on installation.

Fram

The Fram is low priced at £4.75 from my local factor. The filter element material felt about average, but sadly there isn't very much of it, only 84cm2. The canister and crimp are also average, and the main seal is only a light interference fit in it's groove. This filter does, however, have a good quality silicone anti-drain valve. The bypass valve is nitrile, and looks exactly the same as the one from the Halfords filter. I wasn't terribly impressed by the surface rust in the canister, even though it is in the dirty oil side of the filter.

Nipparts

The Nipparts filter is low priced at £4.88 from a local factor. Construction of the canister, end plate and crimp is good, with the end plate having the main seal crimped in place. This seems to be a common trait with the Japanese filters. Filter material felt average, but once again, there isn't much of it. It was also a very orangey colour! In fact, it is currently the worst of the group tested (so far). The anti-drain valve is formed nitrile, but the bypass valve is metal on metal.

To give you some idea of the difference in filter area, here is the highest and lowest one side by side. Genuine Honda is on the left, Blueprint on the right.

Comparisons

Conclusions

The Champion is reasonably priced, has a good filter area (2nd highest), good overall construction, but a poor anti-drain valve let it down. In fact, it wasn't just poor, it simply didn't work.

The Halfords filter is also well priced and readily available. It has the a lowish filter area, the material is thin, and the overall construction and design (valves sealing against cardboard filter ends etc) seemed lightweight. Having said that though, it appeared that it would basically do the job as it didn't have any one particular weakness.

The Blueprint filter is pretty cheap, and it shows. The low filter area and a poor bypass valve that would allow oil to bypass all the time.

The Genuine Honda filter is the most expensive, and this also shows. The largest filter area (nearly twice that of the Blueprint filter), valves that worked (and looked like they'd work properly at all temperatures/conditions), solid overall construction, and a main seal that won't get displaced when trying to install the filter with oily hands, flat on your back.

The Fram is low priced and readily available. It had a good quality anti-drain valve and reasonable bypass arrangement. Sadly, it had a pretty poor filter area.

The Nipparts filter is low priced and again it shows. It has a good main seal, average anti-drain valve but poor bypass valve and poor filter area.

It has to said though, that I've only looked at these particular filters, and it may well be the case that other suppliers are used by the above brands for different filters in their range. But with the selection I looked at, I came to the conclusion that cheap means cheerful. The savings on the aftermarket filters aren't exactly huge, so I'll be sticking to genuine filters from now on. I have been surprised no two filters are the same. It does make you wonder about all those other parts like cam belts, brake pads, water pumps, ball joints, dampers etc. that we assume are all made by the same company really, but in different boxes! I'm hoping to buy some filters from some other big brand names Cooper and Crossland when I can find them, so I'll update this page when I do.

Manufacturers Claims

The Halfords box says "Quality assured. Engineered for ease of fitment and performance"
The Fram box says "The brand name that guarantees QUALITY"