yes, no noticeable change. prius is tuned for stock systems. it's difficult to improve mpg's or power with any known aftermarket products.
I've used K&N filters on all my cars. None of them have shown any improvement in fuel economy or performance. I continue to use K&N for the simple fact that it saves me money in cleaning versus replacing the paper filter.
I've got over 60,000 kms on our original engine air filter. Checked it lately, it's "starting" to show a little soot, ie: you can tell where the air flow's coming in. But really nothing serious. With an item that needs changing this infrequently, I see no point to using anything but OEM. And even if it was a more dusty environment, needing more frequent changes, it's still fairly trivial. I've used K&N oiled air filters; seems to me you're gambling, with your ability to oil it "just right". Oil to much, you're reducing air flow. Oil too little or incompletely: you're letting particles through. Too much hassle.
Be careful with K$N filters! Do you know what a Mass Air Flow Sensor is? Have you ever cleaned out a Throttle Body? (Note: Paying a dealership to laugh at you behind your back and MAYBE spritz some cleaner into your intake doesn't count!!!) K$N filters have a proven history of oil contamination with these components for those people who bother to regularly clean and re-oil their filters. They're junk. Period. Here's the thing with engines and fuel efficiency. If you think of engines like air pumps, then putting a K$N filter into the motor is like running around the block REALLY fast and breathing in through your mouth and breathing out through a straw. In other words.....IF THERE WAS a significant difference in air flow into your motor (spoiler alert: There isn't!) ....then unless you uncork the exhaust, there's still going to be about the same air going in and out. If you have a large displacement motor, and you also modify your exhaust and diddle with your ECU then you can achieve some BHP increases with K$N filters but these gains will come at a price.....actually two prices: More dirt (or oil) in your intake......or.......more fuel burned more quickly. Remember, paper/fiber filters are pretty good at trapping dirt while still providing acceptable air flow. Have you bought a vacuum cleaner lately? Same deal. K$N air filters act like a large oil impregnated cotton-gauze filter....mostly....because that's what they are. They allow more of everything to flow into the intake because instead of being pretty good at trapping dirt while providing acceptable air flow, they're pretty good at providing air flow while trapping dirt at an acceptable level. So...... There may be a statistical cost benefit for K$N filters IF you assiduously clean and re-oil them.....AND if you're capable also of maintaining your intake system yourself.....AND perhaps if you reduce your oil change interval. After all.......more air=less filtration=more dirt in the combustion chamber. All that dirt has to go somewhere... Finally..... There are bunny-huggers out there who make a point that K$N filters will reduce land-fill use. I'll stipulate that this can be a valid point....but some people may be reducing one form of pollution (refuse in land-fills) but increasing others (air particulates, oil run-off, reduced OCIs, etc....) Your call. There are a lot of opinions out there. Due diligence is required. Best of luck!
Firstly, I'd check with TOYOTA to see if it affects your warranty. They'll probably come back and say, yes, warranty will be voided if a warranty claim is attributable to that item. Additionally, if you did change it, you should submit your vehicle to have the emissions checked to ensure it still complies. Personally, I could see the benefit of changes to intake, aerodynamics, exhaust etc in cars of the '50s - '90s (and earlier of course), but these days, with manufacturers spending a lot of effort to improve efficiency and to comply with emissions and CAFE fuel economy requirements, with fairly complex computer controls, I'd be very surprised if you could better the manufacturer's equipment. With Prius, designed for maximum efficiency, I'd suspect you'd go backwards.
Isn't it the case that once computers started monitoring and controlling the air/fuel mixture, unless your filter is near-totally clogged, nothing much happens?
Toyota spends hundreds on LED lighting to save perhaps 1/4 MPG, if they could save any MPG by spending $45 they would. Either it does not save any MPG, or it causes them to fail a safety/emissions test. What is your theory why Toyota does not use K&N filters if they improve MPG?
One potential downside to K&N filters if you are not checking/cleaning it yourself is that they are often ignored by mechanics doing routine maintenance. Since they are darker it's not as obvious when they become dirty.
Prius engine small displacement design to run at low rpm and turns off, so a high flow air filter won't do much unless you plan to race and run the engine at 5000 + rpm most the time! Also using a oil base air filter may coat flow sensor causing inaccurate reading to the ecu either excess rich or lean mixture prolong use may cause damages to engine voiding mechanical and emission warranty! save a few bucks end up spending thousand!
K&N is intended only for modified engines. Carb or FI, you have to retune the system to get any real advantage. They have better airflow than stock filters, but unless your fuel map and exhaust is reconfigured to maximize HP, you won't see any real improvement. Being able to clean the air filter seems nice...especially for applications where replacement filters are expensive (e.g., motorcycles), but overall, it's not much of a savings for cars.
Thanks for all the replies, majority rules. I'll stay away from the K and N filter, don't want to cause any problems later down the line.
If i had to guess, no manufacturer can make a K&N filter comply with US pollution laws. (Why do vendor use exotic element spark plugs that last 100,000 miles? Because the EPA favors disposable parts or permanent parts over maintainable parts. By out lasting the EPA warranty, they make the Feds happy. I suspect an air filter that needs maintenance, is a bad idea to the EPA)
