Filter Elements
Most oil filters have filter elements made of paper and are effective down to about 40 microns. To the right is a paper element expanded 50 times. In this picture, a 30 micron particle is about this big:
o The advanced filters have composite elements made of paper, cellulose, and fiberglass, and are effective down to 15 microns or less. Typically these advanced filters also have more surface area on their elements, and therefore more capacity. To put this into perspective, 25 microns is about 1 thousandth of an inch. In your motor, most parts like pistons, bearings, and bushings are set up with a clearance of 1 thousandth of an inch, so to the moving lubricated parts a 25 micron particle is as big as the oil film, and will scratch both surfaces. We don't want anything in our engines that is 25 microns or bigger. Some companies claim that even particles as small as 1 to 5 microns cause premature engine wear, but I don't find the evidence on this topic to be compelling, either for or against. Anyway, you can see now that standard paper filters are marginal. The paper filters let through about 10 to 20 times as much 25 micron stuff as the synthetic filters do, and about 5 to 10 times as much 15 micron stuff.
To the right is a synthetic element expanded 50 times. It's not enough to ask a company to what size particle their filter is effective. Imagine a screen door with some oil on it. Obviously something the size of a golf ball or fly is simply not getting through. However, even particles which are a tenth the size of the holes sometimes don't get through - spray your screen door with a garden hose and see what comes off. Oil filters are similar, except the holes are random in size, not perfectly regular like a screen door. So, company A says "Our filters are effective down to 7 microns." What does this mean? If "effective" means "we catch 15%," well, I'm not impressed. You need an efficiency number along with the size number before you can really think you know something. No filter is 100% effective - this would require either very regular holes, which are currently impossible to mass produce, or very small holes on average, which would block too much oil flow.
Purolator makes filters in three qualities, standard, premium, and Pure One. Purolator states that their premium filters capture 97.8% @ 30 microns and 85.2% @ 20 microns. These numbers are typical of a normal paper element oil filter. The Purolator Pure One filters capture 99.8% @ 30 microns and 99.2% @ 20 microns. This means the Premium filter is letting through eleven times as many 30 micron particles as the Pure One, and eighteen times as many 20 micron particles. Clearly, the Pure One filter is doing a considerably better job of cleaning the oil than the premium filter.
The way the Pure One achieves this filtering efficiency is by combining three different types of materials in their filter: paper like everyone else to catch the big stuff, and cellulose and fiberglass fibers to fill in the "large" holes in the paper with their much finer fibers. Filters like this are now made by Purolator, Hastings (marketed as AMS), and Champion (marketed as Mobil 1 and Bosch). Accordingly, the best oil filters are the Purolator Pure One, Mobil-1, AMSOil, and Bosch. If you use one of these filters with one of the commercial synthetic oils listed above, you have the best protection money can buy.
Champion says the Bosch is a 15 micron filter, and the Mobil-1 is a 10 micron filter but gives no efficiency numbers. AMS claims their filter is effective to "7 to 10 microns," but again without any efficiency number. Fram makes a new filter, the X2, which they claim is in this category, but I'm skeptical of all things Fram. In particular, in the letter below you will see that a Fram employee seems to indicate that all Fram filters have a rating of 10 microns, which calls into serious question how they measure their paper filters, and also why one would pay three times as much for their advanced filters given that they have the same rating as their basic filters. SAE tests would tend to indicate that the Purolator has a slight advantage in filtering over the other filters named here. The important thing is, all of these filters have performance at 30 microns which is far superior to a paper only filter, and all of these filters have performance at 20 microns which is also far superior to a paper filter. So, bottom line, these filters will clean your oil far better than a paper-only filter.
Of these five filters, only the AMS is specifically recommended for motorcycles, the rest are car filters. If you call the tech support people (I have) and ask what the difference is, you will likely not get a meaningful answer. I certainly didn't. I don't imagine that Honda makes special low-quality oil pumps just for their water-cooled 100 hp/liter four cylinder motorcycle engines, as opposed to their water-cooled 100 hp/liter four cylinder car engines. Maybe 30 years ago Triumph and Harley made suspect oil pumps with strange characteristics and we're still living down some old mythology. Maybe the filter companies don't want legal exposure in the US to a very small group of customers who often use their engines like they're in the Daytona 500. Maybe Honda wants you to buy their mass-marketed paper filter for $12 instead of buying a mass-marketed paper filter from Wal- Mart for $2. If you think Honda car engines are completely different from Honda motorcycle engines, go drive an S2000. Lemme tell you, it's a 4-wheeled motorcycle. Tons of fun, too.
All filters have to undergo SAE (Society of Automotive Engineers) tests to prove that they meet the engine manufacturer's requirements. The SAE J806 test uses a single-pass test, checking for contaminant holding capacity, size of contaminant particles trapped, and ability to maintain clean oil. As an amendment of the J806 test, the multi-pass test also looks for filter life in hours, contaminant capacity in grams, and efficiency based on weight. The efficiency of the filter is determined only by weight through gravimetric measurement of the filtered test liquid. Typical numbers for paper filter elements are 85% (single pass) and 80% (multi-pass). A new test, the SAE J1858, provides both particle counting and gravimetric measurement to measure filter capacity and efficiency. Actual counts of contaminant particles by size are obtained every 10 minutes, both upstream (before the filter) and downstream (after the filter), for evaluation. From this data filtration ratio and efficiency for each contaminant particle size can be determined as well as dust capacity and pressure loss as a function of time. Typical numbers for paper element filters are 40% at 10 microns, 60% at 20 microns, 93% at 30 microns, and 97% at 40 microns. This means a paper filter passes about 25 times as many 30 micron particles as a Pure One. I would love to see these numbers for the various available filters, but no one seems to be talking.
There's a new type of filter being marketed, the "laser cut stainless steel filter," which we're told is "good for the life of your vehicle."
These filters typically have 35-40 micron holes, which is really not acceptable. They typically have 30-40 square inches of filter material, which is really not acceptable. A paper based element is a 3 dimensional filter - when a particle gets stuck deep in the filter element, oil can still flow around it. The stainless steel elements are 2 dimensional - when a particle gets caught, one of the holes is clogged up.
I don't see how you can assure that all the holes get cleared out when you clean these. Certainly simply soaking the filter in kerosene is not going to release particles that have been jammed into a hole at 60psi. Blowing the filter out with air sounds good, but a motorcycle filter is too small to let an air hose inside.
These stainless steel filters cost about $120, about 25 times what I pay for a Pure One. Since I use my filters for about 8,000 miles, that means I have to go 200,000 miles to break even. I've never put more than 60,000 miles on a vehicle.
I don't think this technology is ready to use yet. When the holes get down to 20 microns, and the surface area up to about 100-150 square inches, then I think I'll consider using one. Meanwhile, "good for the life of your vehicle" is not an impressive claim if the device shortens the life of your vehicle.
Another interesting filter is the CM Racing filter. I don't actually know anything about it. It does look interesting.