What are y’all’s thoughts on the reusable K&N air filters?
By reusable, I assume you mean the oiled ones that you wash, reoil and reuse. IMO, they're not worth the hassle. The filter itself flows very well because it's almost like letting your engine breathe through a cheesecloth, making it barely a filter at all. It'll catch the larger objects, but the finer dust and debris get sucked right into your engine. To help with its insufficiency, it's soaked in oil so the finer particles will stick to it. This is better, but still a bit of a crapshoot. Then, there's the common problem of them being over-oiled. The tiny oil particles ride the air stream and get stuck on the MAF sensor wires, skewing its readings. Even if you oil it perfectly to the manufacturer's specs- how do you know none of that oil, even in the "proper" amount, being sucked on for thousands of miles still doesn't gum up the MAF? You won't find out for a long time. You're introducing another maintenance item that now makes your MAF a regular maintenance item as well as subjecting it and your engine to more dirt/damage.
I currently have a Purolator One filter as a read great things about how well they filter. But I also know with good filtration comes less air flow.
Is the K&N filtration good enough? I understand they’re meh at filtration but have excellent air flow.
Generally speaking, yes- reduced flow. Flow is volume. This is why the air filter panel is so large compared to the size of the throttle body inlet. Even though the filter media reduces the flow, it's multiple times larger than that little 3" hole the engine is sucking through. Even then, the engine is only sucking through a fraction of that 3", unless you constantly drive around with the pedal to the metal. So, the stock filter design can flow more than sufficient volume while adequately cleaning the air- as a filter should do. Say you did slap a higher-flowing, but lesser-effective filter in there. What would you get- maybe 2-5 horsepower at wide open throttle at 5,000 RPM or higher? Great. For the 99.9% of your other driving, you're not getting any benefit of any extra airflow over the stock setup. But, what you
are getting at idle, at WOT and anywhere in between is dirtier air.
Is reduced oil and engine life worth the power that isn't there until you're revving to near redline, and, even then, aren't likely to feel?
Would you rather have 300 horsepower for 300K miles or 305 horsepower for 200K miles?
If you absolutely wanna use a reusable filter, I can strongly recommend the AEM DryFlow. K&N owns AEM (or vice versa) so the dry/oilless K&N might be the exact same filter. I've been running one for over 50K miles. I've had my intake tube off four times since installing that filter and, every time, that tube is spotless on the inside. It passes the white glove (actually a white paper towel) test with flying colors.
