What is The Best Oil Filter for a Harley-Davidson Milwaukee 8?

By Gabe Carrera, Esq.
Feb. 5, 2023

Is the money you spend on your oil filters worth it? Have you ever opened up one to see what your money is actually being spent on? I was performing some research for my own HD M8 Road Glide Ultra that I am currently rebuilding from a 114 up to a 117. From my last Hoka hey Motorcycle Challenge in 2022 I seized up the bearings on my flywheels. I had to split the cases to get to the flywheels, thus my chance to upgrade without losing much on gas mileage. Leaving South Dakota to Connecticut to visit my mom who passed away one hour before getting to her I noticed problems with my moto. My engine was getting extremely hot and my performance nose dived greatly.

**Motor oil blowing to the side of the HD M8 motor!**

I decided to do some research on cooling and conducting preventive maintenance since I would have my engine wide-open having extensive open heart surgery! I started by upgrading my cam plate and oil pump to an S&S product. Replaced the plastic Harley cam guides to an S&S cam guide part. I made other changes knowing that S&S engines suck in my opinion, but they do make certain parts for Harleys that are superior in nature, again in my most humble opinion.

Many people ask me what qualifications as an Attorney do i have in giving motorcycle mechanical advice? I agree as an Attorney I should not. Now, as one that completed the certified training at American Motorcycle Institute in 1987 in Daytona Beach I think i have what it takes. NO! I am not going to change your oil if you hire me for legal work!

This first video below caught my attention since it deals with Harley M8 oil filters. This video compares Amsoil KN, Wix, and two Harley OEM filters.

Brad The Wizard Opens Oil Filters Showing Us The Truth!

IN THIS VIDEO WE CUT OPEN THE NEWLY RELEASED HARLEY DAVIDSON MILWAUKEE 8 HI CAPACITY FILTER (part # 62700296 / 62700297 ) AND COMPARE IT TO THE CURRENT M8 / TWIN CAM FILTER (part # 63798-99A / 63731-99A ) AND AGAINST K&N, AMSOIL AND WIX FILTERS
Brad the Wizard!

Brad the Wizard in his video looks at the different paper or cloth filters. He looks at the bypass valve and parts that come with the filters. Brad, if I heard correctly, states that the Wix filters are the best. Them comes one of his viewers in the comments writing one long ass comment that actually gives us all a teachable moment that adds value to the discussion. J Eber commented on the YouTube video with this awesome argument why the K&N filter is the clear choice in the battle of oil filters.

J EBER YouTube Commentator Disputes the Wizard’s Conclusions!

When referring to particle sizes in regards to oil filters, it is important to realize exactly how small the particles being discussed really are. Then, we can discuss the filtration effects of the filters in question in regards to engine life. There is a misconception when it comes to oil filters, that the smaller the micron rating the better the filter. Some companies rate their filter as a “5 micron” filter, which means the filter will catch particles microns in size with at least 50% efficiency. Let’s put a 5 micron particle in perspective. 1 micron is .001mm (or .00003937 inch), so 5 micron is .005mm (.00019685 inch). The tolerances in your engine will be no smaller than 2.5 thousandths of an inch (.0025”). So, 2.5 thousands of an inch, which is equal to a 63.5 micron particle. A 5 micron particle is smaller than a human red blood cell, and too small to see with the naked eye. So how can a particle that size cause damage to your engine?

Next, let’s consider the purpose of an oil filter bypass valve. A bypass valve opens when the inlet side of the filter gets too restrictive. This can happen when the engine is cold and the viscosity of the oil is high (due to the weight of the oil), but this primarily happens when the filter media gets too restrictive or clogged. This is done to keep catastrophic engine failure from occurring; dirty oil is better than no oil. The lower the pressure relief rating, the sooner the valve allows unfiltered oil to enter your system. The last factor that contributes to the bypass opening is the amount (surface area) of the filter media used in the filter. A filter that has a high surface area is going to hold more contaminant and promote good oil flow for a longer period of time, so the bypass will take longer to open.

If the filter you use is 95% efficient at 5 microns it is going to remove more contaminants than a filter that is 3% efficient at 5 microns. The question is, how long will it take for those filters to load up with contaminant and enter bypass? The answer is simple, the more efficient filter will load up sooner, but at what expense? Oil flow is necessary to lubricate rotating parts, prevent engine failure, and help keep the engine cooler, plus again dirty oil flow is better than starving the engine of oil completely (the theory behind the filter bypass). Clean oil is best for long engine life, and a filter that can promote clean oil flow consistently for a longer period of time is a key component of any healthy engine.

When you are talking about filtration, whether it be oil or air, there is a balancing act that has to be performed to ensure your engine gets the protection it needs while giving your engine the most flow possible. Unfortunately, when the focus is an oil filter that is catching extremely small particles at a high percentage, the tradeoff is flow rate. This put the consumer in a “Catch-22” situation. Do you use a filter with the most efficient media at the smallest particle rating, and have the bypass open letting unfiltered oil through the system? Or do you have a filter that does not filter as small a particle size, but filters more of the oil for a longer period of time? K&N filters are designed to give you the balance of oil flow and filtration. Of course, we would like to say we have the most efficient filter at the smallest micron range, but the fact is we are not going to sacrifice oil flow or the quality of filtration by having a high efficiency filter that operates in bypass mode for 80% percent of its life. I know for me personally it’s a simple decision, the small particle filtration does not mean anything to me since we are talking about particles I can’t see, especially if there is a remote possibility of unfiltered oil touching my bearing surfaces causing premature wear and eventual engine failure.

**My 2019 HD RGU building from a 114 to a 117!**

When you are comparing filters, to make the most informed decision possible, look at the following things (with the least amount of emphasis on micron rating): Filtration efficiency, Filter surface area, bypass setting.

The KN-171 filter has a nominal micron rating of 25, meaning it will capture 25 micron particles with at least 50% efficiency. The filtration efficiency of the KN-171 at 5 microns is 3%. The KN-171 also has 165 sq.in. of filter area partially the reason it flows 25% better than the OE, paired with a bypass that opens at 14psi. The Harley Davidson filter 95.8% efficient at 5 micron and 98.6% at 25 micron, it also has 63 sq.in. of media and a bypass that opens at 10psi. This means the Harley filter will run in bypass mode for a significant portion of its installed life, whereas the K&N will allow oil to flow through the filter for a longer period of time. In my personal opinion, this makes the K&N filter the clear choice. Here is a side by side to the amount of media inside of a K&N filter and your typical OEM filter (I don’t think it is Harley’s current one but look cool).

Honda Man Opens Up 7-Oil Filters For Quality Check!

The Motorcycle MD has a channel on YouTube focusing in on Honda bikes. I am placing his video here because he goes in depth on oil filters to the Attorney That RIDES’ satisfaction. below is what he states about his YouTube channel and videos.

About Me– My name is Cody Richards. I’m a MMI graduate and Red Level certified Honda technician who likes to consider himself as a lifetime learner. I’ve been wrenching as long as I can remember and have had the privilege of working under some amazing technicians, some with over 50 years in the Honda motorcycle world. I took these opportunities over the years to soak up as much knowledge as humanly possible so that I could continue to improve upon common techniques, mistakes, and bad habits. I stay active with new training from Honda as well as work Full-Time at a factory Honda repair shop. I want to help people who are passionate about motorcycles feel confident in their own repairs and maintenance which will ultimately save you money, make you more aware of common issues and help you to diagnose your bike’s problems fast and efficiently. I stay active on my website www.Themotorcyclemd.com with good tips and tricks. I hope you find this content useful!
Merch coming soon
The Motorcycle MD

The Best Harley Davidson Oil Filter – Where was it made?

Jay W. Case is a Harley mechanic who also has a shit load of YouTube videos on motorcycle repairs and reviews on products for you to do research to keep your ride healthy! here is the last video i am going to post but know that there are many more videos and articles for your research specific to your motorcycle.

Harley Davidson Doesn’t Want You to see inside the New Oil Filter – vs Fram

You can support this Moto-Blog by referring your family and friends to Attorney Gabe Carrera with his office in Fort Lauderdale, Florida. gabe practices in the area of Injury Law (moto, auto crashes, slip & fall, ect) and Family Law (Divorces, paternity, custody, domestic violence). AttorneyThatRIDES.com – TEL: 954-533-7593 (24/7).