Latest Reader Questions: Reusable Air Filters & Engine Designs

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Here are the latest reader questions, along with my replies!

Rod asks: Long time reader who sports your stickers on my laptops. Would put one on my car but the wife hates stickers and I’d rather just keep the peace. I have a question about aftermarket oiled air filters (like the popular K&N type). I ride both a motorcycle and drive a 2006 MX-5. I have a K&N on my motorcycle, and a stock filter on the Mazda. I have been considering switching to an aftermarket oiled filter for the car. I keep up meticulous maintenance on all my vehicles, and regularly clean and oil my motorcycle filter. I have noticed that some of the commenters on your posts have mentioned that aftermarket filters have been detrimental to their vehicles, causing them to need piston ring replacement and other repairs. Other people rave about them.My motorcycle mechanic tells me that most people over-oil these filters, causing the butterfly valves and intakes on bikes to be coated with gunk, which decreases performance. Also, if you under-oil them, they can cause particulates to pass through. You have always been my first go-to for info on vehicles, and I was wondering what your opinion is on using these types of filters, and whether they are a worthwhile choice. Thank you for your time!

My reply: I “amen” what your bike mechanic told you. It is very important to not over (or under) oil the filter, for exactly the reasons described. With modern cars (modern bikes, too) there’s an additional potential problem from over-oiling: excess oil may leach onto the fuel-injection system’s airflow sensor and so on.

So, if you use a K&N or similar, be absolutely sure you use it correctly. This includes the cleaning and re-oiling process especially. I’d also be certain that using one of these filters will not affect warranty coverage.

That said, I use K&Ns on several of my bikes and also my old muscle car – and haven’t had any problems. The main upside – in my opinion – is that these filters are reusable, which over time can definitely save you money. And there is a benefit in terms of airflow, too – especially vs. some of the cheap/off-the-shelf paper (dry) filters.

The key thing is keeping up with the maintenance of the filters (cleaning/oiling) which I suspect you would, given that you seem to be a pretty maintenance-persnickety guy, just like me!

. . .

James asks: Eric, I am one of those who does not consider myself a car guy and yet the episodes with you on the Tom Woods Show are some of my favorite. I don’t listen to every episode anymore but every now and then find myself going, “When are we going to get another Eric Peters episode?” Anyway, I was just wondering your opinion on the idea that gets thrown around sometimes about the auto industry buying patents for more efficient engine designs and then just sitting on them. Is this true? Is it because there is a relationship with the oil industry such that they want less efficient cars? Thank you.

My reply: It is certainly possible. What I know for certain is that the government has effectively suppressed (using regulatory pretexts) extremely fuel-efficient diesel engine technology. VW was working on a prototype diesel-powered car capable of 80-plus MPG. The “cheating” scandal likely destroyed any chance of that vehicle ever seeing the light of day.

I also know for certain that it would easy for the car companies to build/sell compact cars powered by small four-stroke gas engines (nothing exotic; the same kinds of engines in use today) capable of similar mileage… if the government allowed them to build/sell cars without six air bags and which didn’t have to pass “safety” tests – meaning, government bumper/impact requirements – and which could therefore be built light – curb weight around 1,800 pounds or so, about the same weight as an old (classic) air-cooled VW Beetle. Such a car, with an engine around 1.5 liters in size, could easily average at least 60 MPG.

I have been arguing for years that my “safety” (and yours) is none of the government’s rightful business. If we wish to buy a small/light car because it is small and light and so delivers very high mileage – and are are willing to accept that such a car won’t protect us as well in the event we get into a crash – well, that is our business, isn’t it?

Those who think it’s not our business – and make it their business – are insufferable busybodies. And also thugs. Because they aren’t suggesting – they are insisting, and using force to back it up.

It’s an outrageous thing, when you examine it closely. Who do these people think they are? Our owners? Our parents?

If we are free people then we have the right to freely assume risk for the sake of reward – or for whatever reason seems right to us. The only legitimate reason for forcibly interfering with another human being is when that other person has done something which causes a tangible harm to other people.

Otherwise, leave us be!

 . . .

Got a question about cars – or anything else? Click on the “ask Eric” link and send ’em in!

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