The stock oil filter on the SHO V-6 is the Motorcraft FL-400A. The Fram equivalent is the PH3600. Some SHO owners use the more expensive and difficult-to-find (especially if the rumors of Fram's discontinuation of the HP-1 are true) Fram HP-1, which appears to be just a larger filter. Here's what one SHO owner found when he compared the two filters with help from the Fram technical department:

**Oil Filter Comparison: Fram PH3600 and HP-1**
Characteristic	PH3600	HP-1
Diameter	3"	3 5/8"
Length		Longer
Anti-drainback and relief valves	Yes	Yes
Size of particles trapped	15 microns	20 microns
Max pressure	250-300 psi	500 psi
Flow rate		Higher

From this data, it is logical to conclude that there is no advantage to using a HP1 on a SHO unless your engine is modified with a high capacity oil pump and has much higher than stock oil pressure. The PH3600 appears to filters better in a stock engine and costs alot less. Appearances aren't always what they seem, though. As one of the users of the HP-1, this data piqued Gary Morrell's interest, and he called an engineer at Fram's Design Engineering Group. This group frequently works with Ford Motorsports on racing programs. Here's the rest of the story in Gary's words:

Oil filters are tested to SAE J-608, which is a battery of standardized tests that looks at, among other things, a filter's pressure drop -vs- flow, relief valve cracking pressure, relief valve flow characteristics, and the Single Pass Filtering Efficiency (SPFE).

The PH3600 is rated at >90% SPFE for beads of 10 to 20 microns ( a micron is 3.937 X 10^-5 inches, or 0.00003937" ). In other words, it will trap >90% of 10 to 20 micron particles with only one pass thru the filter. The HP-1 and the PH3600 use the same filtering media, the HP-1 just has considerably more media area. The HP-1 is slightly less efficient at trapping small particles because it's SPFE was tested at a higher flow rate than the PH3600. As the flow rate increases, the fluid face velocity at the filter media increases, making it more difficult to trap fine particles.

One could see how a filter manufacturer could play games with the SPFE numbers, and according to Fram, they do. Obviously, any good oil filter is capable of catching 5 micron particles, but the SPFE might be <20% for particles this size. Without the SPFE percentage, claiming that your filter will catch sub-atomic particles is advertising hype. BTW, small particle SPFE improves as the filter gets dirty because the larger passages get plugged, forcing the fluid thru the remaining smaller passages, so a dirty filter coud test more efficient then a new one. SAE J-608 specifies that a new filter is used.

The PH3600 is rated 15 microns SPFE at 3 GPM, the relief valve opens at 6 to 12 psi. At 9 to 12 psi, the relief valve will flow 0.1 GPM, at 15 to 17 psi, the relief valve will flow 3 GPM maximum, due to its orifice size. Fram has not tested the pressure drop-vs-flow beyond 3 GPM, but the pressure drop is <2psi at 3 GPM.

The HP-1 is rated 20 microns SPFE at 10 GPM, the relief valve opens at 9 to 12 psi. The relief valve characteristics are similar to the PH3600. HP-1 pressure drop-vs-flow data:

All this gets a bit more interesting when you plug the SHO's stock oil pump flow rates and pressures into the equation, read on...

The Yamaha is a high clearance engine, bearing-wise. It relies on a high volume of oil at moderate pressure to lubricate and cool the bearings. The oil pump is rated to deliver 12.1 GPM @ 43 psi at 6400 RPM crank, which, BTW, is the entire 5 quart oil sump every 10 seconds. The maximum oil pressure that the pump can develop is 57 psi +/-5 psi.

Frankly, I'm a little nervous stuffing 12 GPM thru a filter that's only been tested to 3 GPM.

Ford's spec for the oil filter is 10 GPM with a relief valve rating of 21.5 to 28.5 psi. This means that the filter could conceivably drop some 28 psi before the relief valve opened. That represents a 50% loss of the nominal oil pressure that the pump can deliver. When I mentioned this to the Fram engineer, he was, to put it mildly, amazed. A 50% pressure drop at the filter means that 50% less oil is getting to the bearings. This also makes me nervous.

I studied the benefits and detriments in switching from the PH3600 to the HP-1 and decided that sacrificing a small bit of filtering efficiency was well worth getting more oil to the bearings. I also asked the Fram engineer if I had made a good choice in switching, and in light of the flow rates we had discussed, he was in complete agreement. His feeling is that the PH3600 is in full bypass at 12 GPM, assuming it can flow that rate at all without becoming a complete cork, but, the PH3600 has never been tested to that degree, so we really don't know.

In summary, the biggest hassle I have with many aftermarket oil filters is that they haven't been tested beyond 3 GPM. The HP-1 has, and that's why I use it, and recommend it.

The only other way around the pressure drop situation is a bypass oil filter. These work by diverting a portion of the oil pump's output thru a very fine filter, typically <5 microns, while the majority of the oil goes directly to the engine. If you tried to ram all the oil flow thru a <5 micron filter, the pressure drop would be excessive, unless the filter had enormous surface area. Amsoil has a very nice bypass system, so does System 1.

Fram has just released an expanded line of racing oil filters that have all been tested to at least 10 GPM. The HP-10, which replaces the stock PH3600 filter, looks just like the PH3600, so it will fit on an automatic SHO (the HP-1 does not). However, because it's a high flow filter, the ATX SHO fanatics won't have to worry about oil starvation at the higher (where all SHOs like to be) RPM ranges. The new line of filters was released April 1, so they might not be in stores yet.

Other aftermarket oil filter options (with SHOtimes subscriber comments included) include :

Now, on to oil filtration. Even having taken care of all other issues relating to oil contamination, there is still a certain amount of dirt and debris in your oil which must be taken care of. Hence, there is a necessity to maintain adequate oil filtration in order for a lubricant to remain viable. Even though the extra dispersancy additives keep dirt and debris surrounded and impede contact with engine components, those contaminants must still be removed. This is where your oil filter comes into play.

First of all, the statistics previously mentioned regarding engine wear haven't changed. 60% of all engine wear is caused by particles between 5 and 20 microns. Unfortunately, most oil filters on the market today are lucky to remove even a small percentage of particles under 30 to 40 microns. This, again, leaves most of the harmful debris in your oil.

The actual filtration efficiency of a particular filter really depends upon the filter manufacturer, and it is sometimes very difficult to get any specific numbers from them regarding their filters' actual filtration efficiency.

To make a long story short, the researchers had this to say:

"Abrasive engine wear can be substantially reduced with an increase in filter single pass efficiency. Compared to a 40 micron filter, engine wear was reduced by 50 percent with 30 micron filtration. Likewise, wear was reduced by 70 percent with 15 micron filtration."

So, as you can see, any increase in filtration efficiency that you can avail yourself of will be of great benefit to your vehicle's protection and performance.

If you do any research on your own, you'll find that most manufacturers no longer use micron levels to rate their filters. This is a result of some manufacturers' shady representation of their filters using micron ratings. You see, some filter manufacturers would indicate that their filters would remove x micron particles and leave it at that ("x" being whatever arbitrary number they chose to print). Of course, consumers would take this to mean that all particles larger than this micron level would be removed, which is not necessarily the case.

The truth is that chicken wire will remove 5 micron particles. It will even remove 1 micron particles. BUT, it will not do so with very good efficiency. The key is, how efficient is the filter at removing x micron particles. If you don't know how efficient it is at a certain level, the micron rating means nothing.

So, most companies have gotten away from micron ratings (to avoid the confusion) and have gone to an overall efficiency rating. In other words, an industry standard test is used in which oil is contaminated with a certain number of particles of varying micron sizes. At the end of the test, there is a measurement taken to determine the total percentage of ALL of these particles that were removed by the filter. That percentage is then stated as the overall filtration efficiency of the filter.

Some companies use a single pass test, others use a multiple pass test. Both are perfectly valid and will give you an excellent way of determining how well a filter will do its job, but you should not try to compare results from a single pass test to results of a multiple pass test. You'd be comparing apples and oranges. In either case, high efficiency filters will rank in the low to mid 90's for filtration efficiency. Off-the- shelf filters will rank in the mid 70's to mid 80's for filtration efficiency.

Nevertheless, you may still want to compare filters using micron ratings. If this is the case, the following is a good rule of thumb. A filter is considered nominally efficient at a certain micron level if it can remove 50 percent of particles that size. In other words, a filter that will consistently remove 50% of particles 20 microns or larger is nominally efficient at 20 microns.

A filter is considered to achieve absolute filtration efficiency at a certain micron level if it can remove 98.7% of particles that size. So, if a filter can remove 98.7% of particles 20 microns or larger, it achieves absolute efficiency at that micron level.

Most off-the-shelf filters are based upon a cellulose fiber filtration media. Most of these filters are, at best, nominally efficient at 15 to 20 microns. They won't generally achieve absolute efficiency until particle sizes reach 30 microns or higher.

High efficiency oil filters have filtration media made of a combination of at least two of the following: glass, synthetic fibers and cellulose fibers. Those that use all three are generally the best in terms of filtration. Those that use only two will fall somewhere in between. The best of these high efficiency filters will achieve absolute efficiency down to about 10 microns and will be nominally efficient down to 5 microns or so.

The fact is, you would probably be amazed at how much engine wear could be eliminated simply by using more advanced oil filtration. In paper 881825 the Society of Automotive Engineers indicates that a joint study was performed between AC Spark Plug and Detroit Diesel Corp. The study found that finer oil filtration significantly reduced the rate of engine wear.

According to the paper, the tests regarding engine wear within a diesel engine were performed using four levels of oil filtration. They chose filters whose efficiency rating was very high for particles of 40 micron, 15 micron, 8.5 micron and 7 micron sizes.

The same was done for gasoline engines, except that the relative sizes were 40 microns, 30 microns, 25 microns and 15 microns.

"Abrasive engine wear can be substantially reduced with an increase in filter single pass efficiency. Compared to a 40 micron filter, engine wear was reduced by 50 percent with 30 micron filtration. Likewise, wear was reduced by 70 percent with 15 micron filtration."

By combining this type of oil filtration with the superior protection and cleanliness of a premium synthetic oil, you will virtually eliminate engine wear.

Of course, filter capacity and quality of construction are also important considerations. If a filter has low capacity and high efficiency, it will clog up quickly. As a result, your oil will begin to bypass the filter completely and will become contaminated very quickly. Filters with high efficiency and low capacity should definitely be changed at 3,000 to 5,000 miles or 3 months - without question.

Filters which have high capacity but low efficiency will last longer without becoming saturated, but will not protect your engine as well. Of course, filters with low capacity AND low efficiency are at the bottom of the barrel and should be avoided. Generally, you can call a filter manufacturer and ask them specifically what their filtration efficiency and capacity ratings are for your filter. They should have that information.

If they give you a micron rating, ask them how efficient their filters are at removing particles of that micron size. You might also ask them at what micron level their filters are nominally efficient (50% removal) and at what level they achieve absolute efficiency (about 99% removal). If they can't or won't provide you with a straight answer, I wouldn't purchase their filters.

If they give you an overall percentage efficiency rating, ask them if that is for a single pass test or a multiple pass test. That will be important if you are to compare those ratings with other manufacturers so that you'll be comparing apples to apples.

For those of you who just want to know what's best, here's a breakdown of the top 3, in my opinion. Mobil 1, Pure 1 and AMSOIL provide the greatest filtration efficiency in the tests I've seen. Mobil 1 and Pure 1 both achieved 93% overall filtration efficiency on the SAE HS806 test. AMSOIL scored a 94%.

In regards to filtration capacity, the AMSOIL outscored them by a wide margin. In a comparison of filters recommended for the same application, the AMSOIL could hold 21 grams of particulate matter. Comparable filters from Mobil 1 and Pure 1 held 18 grams and 15 grams respectively. So, the AMSOIL filter held 17% more than the Mobil 1 and 40% more than the Pure 1.

The AMSOIL also appears to have a little heavier construction, but everyone seems to have different criteria they use to judge this. You'd have to cut the filters apart for yourself to make your own judgements in this matter.

The AMSOIL company recommends changing their filters at 12,500 mile or 6 month increments. Based on their numbers, this seems reasonable. They have better capacity and stronger construction which should allow them to achieve longer change intervals. Since AMSOIL filters have been recommended for these intervals for about 20 years, it seems reasonable that they know what they're talking about.

Mobil 1 and Pure 1 recommend changing their filters at your vehicle manufacturer's recommendations. That generally means change the filter at each oil change which amounts to changing the filter every 3,000 to 7500 miles depending upon driving conditions. Because of the lower capacity of the Pure 1 filters, I'd recommend changing them closer to 3 to 5,000 miles. The Mobil 1 would probably last 5,000 to 7500 miles with good results.

As a side note, you can determine if your oil is bypassing your oil filter by touching your filter after at least 45 minutes to an hour's worth of driving. If the filter is hot, you're probably in good shape. If it's not, the oil is likely bypassing the filter, and it is time for a change.

Let's assume you drive 25,000 miles per year. The Pure 1 is about half the price of the AMSOIL or Mobil 1 in most cases, and runs about $5.00 for a filter for a 96 Ford Taurus 3.0L. However, I recommend that it be changed more often due to a lower filtration capacity. With changes at 5,000 miles you're looking at 5 filters x $5 = $25. If you decide to play it a little safer and change at 3,000 miles (which I'd recommend), you're looking at about 8 filters x $5 = $40 for the year.

The Mobil 1 and AMSOIL filters will run you roughly $10 for a filter for that same application. If you take the Mobil 1 to the high end at 7500 miles, that amounts to about 3 filter changes or $30. Playing it a little safer at 5,000 miles puts you at 5 filter changes or $50 for the year.

If you use AMSOIL's recommended filter changes (12,500 miles), that amounts to 2 $10 filters or $20 for the whole year. Seems to me this is the better buy. You get slightly better filtration efficiency and fewer filter changes for less money. Can't see how it gets any better than that.

Of course, the first question that comes to mind when most people hear of high efficiency filtration is oil starvation. How can an oil filter remove particles that much smaller and still provide adequate oil flow to critical engine components?

Well, again I refer back to the high efficiency foam air filter. You'll remember that it is designed to have a much thicker filtration media that will trap particles throughout the entire media instead of only on the surface as with a paper air filter.

This is also how high efficiency oil filters work. Instead of trapping all of the oil contaminants on the surface of a paper (cellulose) type filtration media, high efficiency oil filters have a depth type media which will trap contaminants throughout the entire filtration media. This, combined with the different type of materials used for the filtration media allows high efficiency oil filters to remove more and smaller particles without restricting oil flow - just as high efficiency foam air filters remove more and smaller particles without restricting air flow.

There is also the option of using magnetics to help with filtration. Some filters are magnetically charged so that they hold all engine wear particles within the filter, no matter what the size. These are not necessarily a bad idea, but they do not remove other oil contaminants which are not metallic in nature. Therefore, if possible, you might want to consider some combination of magnetic filtration AND high efficiency filtration media.

The vast majority of oil filters used in automobiles today are full flow filters. With this type of system, all of the oil is filtered before it passes into the engine. Full flow filters must provide low restriction to oil flow while having a high degree of single pass efficiency. This means that a filter must remove as much engine-damaging dirt and grit as possible from the oil on the first time around.

Pleated Media. The majority of automotive oil filters today use pleated filter media, which increases surface area for high filtration efficiency within a relatively small space. However, the number of pleats in the media does not have as much bearing on filtration efficiency as the quality of the media itself. With thicker, high-quality media, the filter design may, in fact, call for fewer pleats to improve fluid flow and filter performance.

Over-pressurized Filters. From time to time, a used oil filter will appear bulged or deformed. A bulged oil filter is one that has been subjected to too much pressure -- a condition that occurs when the oil pressure regulating valve is malfunctioning. When a bulged oil filter is discovered, the pressure regulating valve should be serviced immediately.

What causes over-pressurization? Excessive engine oil pressure is the result of a faulty oil pressure regulating valve. To properly separate the engine parts and prevent excessive wear, the oil must be under pressure. The pump supplies oil at volumes and pressures greater than what the system requires to lubricate the bearings and other moving parts. The regulating valve opens to allow excess volume and pressure to be diverted.

There are two ways that the valve fails to operate correctly: either it sticks in the closed position, or it is slow to move to the open position after the engine has started. Unfortunately, a stuck valve can free itself after filter failure, leaving no evidence of any malfunction.

Note: Excessive oil pressure will cause filter deformation. If the regulating valve still remains stuck, the gasket between the filter and the base can blow out or the filter seam will open. The system will then lose all of its oil. To minimize the risk of an over-pressurized system, motorists should be advised to: Change the oil and filter often.

Oil Pressure Regulating Valve. The oil pump pressure regulating valve, usually built into the oil pump, helps control the operating pressure of the lubrication system. The regulating valve is set by the manufacturer to maintain the correct pressure. The valve utilized a ball (or plunger) and spring mechanism. When the operating pressure is below the preset PSI level, the spring holds the ball in the closed position so that oil flows to the bearings under pressure. When the desired amount of pressure is reached, the valve opens enough to maintain this pressure. Once the valve is open, the pressure remains fairly constant, with only small changes as the engine speed varies. If the oil pressure regulating valve becomes stuck in the closed position or slow to move to the open position after the engine has started, the pressure in the system will exceed the regulating valve setting. This may cause an over-pressurized oil filter. If a deformed oil filter is observed, the oil pressure regulating valve must be serviced immediately.

Relief (By-Pass) Valve. In a full flow system, all the oil passes through the filter to reach the engine. If the filter clogs, an alternative route to the engine must be provided for the oil, or the bearings and other internal parts may fail, due to oil starvation. A relief, or by-pass, valve is used to allow unfiltered oil to lubricate the engine. Unfiltered oil is far better than no oil at all. This relief (by-pass) valve is built into the engine block in some cars. Otherwise, the relief (by-pass) valve is a component of the oil filter itself. Under normal conditions, the valve remains closed. When there is sufficient contaminant in the oil filter to reach a preset level of pressure differential to oil flow (around 10-12 PSI in most passenger cars), pressure differential on the relief (by-pass) valve caused it to open. This condition can occur when the oil filter has become clogged or when the weather is cold and the oil is thick and flows slowly.

Anti-Drainback Valve. Some oil filter mountings may allow oil to drain out of the filter through the oil pump when the engine is stopped. When the engine is next started, oil must refill the filter before full oil pressure reaches the engine. The anti-drainback valve, included in the filter when required, prevents oil from draining out of the filter. This anti-drainback valve is actually a rubber flap that covers the inside of the inlet holes of the filter. When the oil pump starts pumping oil, the pressure will unseat the flap. The purpose of this valve is to keep the oil filter filed at all times, so when the engine is started there will be an almost instantaneous supply of oil to the engine.

Anti-Siphon Valve. When a turbocharged engine is turned off, it is possible for the turbocharger’s lubrication circuit to siphon oil from the oil filter. To prevent this from happening, the turbocharged engine’s oil filter is equipped with a specially designed, one-way, shut-off called the anti-siphon valve. Oil pressure keeps this spring-loaded valve open while the engine is turned on. When the engine is turned off and oil pressure drops to zero, the anti-siphon valve automatically closes to prevent the back-flow of oil. This valve insures that there will be a continuous supply of oil available to the turbocharger and the engine’s lubrication system upon start-up.

Not On Dry Starts: If a vehicle has not been operated for several days or after oil and filter change, some oil may have drained from the filter in spite of the special valves. This is why it is always a good idea to start the engine slowly, letting it run on idle for 30-60 seconds so the lubrication system will be fully charged with oil before a heavy load is placed on the engine.

Magnetic force is a powerful precision device that magnetizes the oil filter and effectively removes and traps virtually all micro-abrasive alloy particles from the oil inside the filter. When an engine is newly assembled, the piston rings do not fit precisely into the cylinders despite highly accurate machining techniques. The piston rings wear to precisely fit in the cylinder during the break-in period. Unfortunately, the wearing of the piston rings and cylinder walls continues, due to micro abrasive particles depositing even more contaminants into the oil. Some of the particles are large enough to be caught in the oil filter. Those that are not, continue to circulate with the oil, passing between the piston rings and cylinders well as through all the bearings. The micro abrasives cause scratches, generating more particles, thereby worsening the problem.

Conventional oil filters, combined with Super MAGNAFORCE, remove virtually all of the micro abrasive particles from the oil. Expansion rings without abrasive metal particles will slowly polish and restore cylinder walls to their "like new" condition; significantly reducing wear. Engine life is dramatically prolonged, delaying or preventing the wear that leads to pollution.

Even high quality oil filters and oil treatments cannot remove fine abrasive alloy particles which cause major engine wear and decrease engine performance.

In order for oil filters to trap particles under 25 microns, the oil filter would need to severely restrict the flow of engine oil. This restricted flow would reduce oil pressure to a critical level (oil starvation) and low oil pressure will, of course, result in engine failure.