Author: Gerhard Bartsch
Intro by Todd Marcucci
Many, MANY thanks go out to all the people that submitted filters to us and provided us with positive feedback and suggestions for the study. A special thanks from ALL of NTPOG and I know much of the Honda community goes to Gerhard for taking the time to carry on this study which we in the club simply did not have the time/resources to do.
What this review is: The purpose of this review is to examine the different filters available for Hondas today, including Honda filters themselves. Most people probably don't realize it, but there are at least 3 different Honda filters (with different part numbers, made in 3 different countries! All happen to be very different, as well.
What this review is NOT: This review contains no SAE or ASTM test data regarding filtration ability or flow information. This data changes often (as do the filter designs) and in some cases is not even available (publicly) from a manufacturer. If you are interested in actual filtration information, your best option is to review the data yourself (contact the manufacturers) and do your own oil test/analysis (see below). The information presented here is intended solely to help you determine which filter is right for you from the stanpoint of construction. We also hope to have done the "difficult" work for you as you probably don't want to spend the hundreds of dollars and hundreds of hours that we have dissassembling filters.
NTPOG makes no claim as to the reliability or performance of any filter presented here, nor does NTPOG accept any responsibility for any damage caused by any filter.
Other "Suggested" Reading
If you are interested in seeing the "original" NTPOG filter review (by Todd Marcucci), you may view it here. Please note, though, that the filter information is VERY outdated. Please refer to Gerhard's data presented in the following review for more up-to-date information.
Finally, we would like to encourage our readers to search the internet for other
sites and articles on oil filters and oil filtration as you will find a lot of
good information. Some other sites to try:
We're going to go over the same things as in the original reviews, but this time we're going to add some more information about oil types, particle sizes, and lab tests.
The majority of this report is going to go over the physical construction of the filter assemblies. One of the first questions to consider is 'Was the filter physically constructed well?' In order to answer that question we are going to take a look at the basic assemblies found in an oil filter, present a number of measurements, and give you a idea of my opinion of the filter's construction.
The above being stated, it's important for you to understand that I am not a chemical engineer or a expert in the construction of oil filters. I do believe that oil filter construction analysis is not rocket science. There are going to be extremely obvious differences that are going help us determine if a filter is well constructed or something that should never be used in your car.
No claim as to the reliability or performance of any filter reviewed here is made. The information contained in this review is used at your own risk.
What Are the Parts of an Oil Filter?
The first picture is the external view of the base. The base is (of course) the point that the filter mounts to your engine. At it's center is a threaded outlet hole. Surrounding the outlet hole on the interior is a flexible gasket (second picture) that overlays a series of holes where the oil enters the filter assembly. The gasket acts as a type of one way valve that only opens to let oil in through the holes to fill the assembly. When oil pressure drops (engine is turned off, etc.) the gasket returns to cover the holes preventing the oil in the whole assembly from leaking into the engine and down to the oil pan. The gasket is generally called an anti-drain back valve.
The filter assembly is generally a pleated piece of material wrapped around a frame that maintains its structural integrity (as oil flows from the outside to the inside and out the outlet hole). Usually the frame is made of metal, but can also be made of cardboard. The seam of the filter material is generally sealed with a strip of metal that clamps to two pieces together under high pressure. However, it the seam can also be glued together. Lastly, most filter assemblies have a by-pass valve installed in their top, and a large hole at their base that fits into the gasket.
The By-Pass Valve
There are a variety of designs for the by-pass valve. Generally, the valve uses a spring loaded design where oil pressure pushes the valve open as pressure builds up from a clogged filter. When a by-pass valve opens it circulates "dirty" oil directly back into the engine to ensure proper lubrication at all times. Usually, the valve is coated in some form of gasket material to prevent leakage.
The Can & The Spring
The spring is usually either of a leaf or traditional design, and usually sits at the top of the can. Being placed at the top of the can causes the spring to push the filter snugly into the gasket at the base. (I suspect this standard design allows manufactures not to keep tight tolerances in manufacturing of the filter assembly. As such, if the filter varies 1mm to 5mm in height then the spring would simply adjust and keep the filter in place.)
How Do You Take Apart an Oil Filter?
The tool is fairly simple. You simply place the filter on the round stud, finger tighten the knob, and turn the can with your hand until it pops off (while tightening the knob as the can turns easier).
The above list is the list of the filters that were physically inspected for the purposes of this review. Additionally, we also inspected the OEM Acura NSX filter, the WEB W-3429 filter, and the Motorcraft FL-2005. These later filters do not fit on the Honda Prelude, but do give it some insights into some other manufacturer's filters.
What are the considerations when looking for an oversized filter? First, it's got to fit the physical space restrictions on the Prelude. This means that it's got to fit behind the engine, have enough clearance between the firewall and the engine, fit the oil filter mounting base plate, and have the same inlet threading (20mm x 1.5mm). Second, the by-pass valve needs to have the relatively same stiffness as the OEM by-pass specification. The reason for this is fairly simple: Too weak a spring will cause the filter to by-pass all the time, and to strong a spring may cause the filter to restrict oil flow and lower oil pressure. The OEM specification is 9-11PSI.
Oil Change Intervals
Honda recommends that you change the oil in your Prelude every 7500 miles. Many dealers attempt to get you change the oil in your car every 3000 miles. Changing your oil every 3000 miles is basically a complete waste of your money, and bad for the environment. (That used oil needs to go somewhere...)
Even the worst of oil filters will last for 3000 miles without any problems at all, and almost any motor oil will last for 7500 miles.
If you use Redline, Mobil 1, AMSOIL, Royal Purple, or Valvoline synthetic motor oils you can easily run your oil in your engine without any problems for the OEM recommended change interval of 7500 miles.
The only time you have to consider changing your motor oil at shorter intervals is if your car is not a daily driver, and will not warm up to full operating temperature for at least 30 minutes a day. The reason for this is that small amounts of moisture (water) in the air tend to soak slowly into your motor oil. (The oil system is not truly closed, even though you have an oil cap.) The water mixes with the oil and other matter in the oil system and forms acids that can eat your engine parts over time. Warming up the engine causes the moisture to leave the motor oil. If you are changing your oil every 3000 miles (because you drive the car once a week) or at a specific time intervals (every 4-6 months because you aren't putting 3000 miles on the oil), then it's not as import to use synthetic motor oil.
Some people will disagree with the above, but the fact is that just about every brand name non-synthetic oil (or "dino") will last 3000 miles and have almost no significant wear to the oil or engine. It is not cost effective to use synthetic oil if you car sits for long intervals with low mileage.
The chief advantages to using synthetic motor oils are typically considered to be better at extended drain intervals, have better thermal stability, better cold flow characteristics, superior additive packages, and a lower coefficient of friction (resulting in lower engine wear and better gas mileage).
Engine Oil Change Testing
I use Black Stone Labs, many other folks use Oil Analyzers. Both companies will send you reports like this:
Notice on the report that I used 10w40 AMSOIL synthetic oil and that the oil was perfectly fine at 6350 miles. The lab indicated that I could be using the oil for a longer interval. I went on to use the same oil for this report with an AMSOIL SDF-44 oil filter for 13500 miles. It turns out that this oil should be changed every 10000 to 11000 miles. I'm still using it, but just changing the oil every 7500 miles with either a Mobil 1, AMSOIL, or Fram x2 filter. (It's simpler to change the oil and the filter at once.)
In addition to giving you an idea as to how well your oil is being filtered, the lab tests show you just what elements are present in the oil. By carefully looking at the list of elements you can determine problems with your engine. The following picture shows a list of elements and their common meaning when present in motor oil:
The biggest advantage to having your oil tested periodically is that you can determine engine component failure prior to the engine actually breaking down. For example: If anti-freeze is found on your oil then you likely have gasket failure of some sort (head gasket). It's probably cheaper to fix the gasket then drive the car until the anti-freeze starts leaking seriously and causes the bearings to fail, etc.
Oil Filter Inspection Information
Honda Prelude Oil Filter Recommendations
What Not To Use: Bosch, STP, and Wal-Mart Supertech
Check back, there are more filters on the way. For comments, questions, or to submit a different filter for analysis, please e-mail the author.
This page last updated 9/1/01.