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Discussion Starter #1
I finally got tired of having to special-order air filters for the Insight, so I ordered a K&N filter instead. Got it Friday, and yesterday filled the tank and headed off on a ~100 mile round trip to visit friends. I do this trip every month or so, and generally have trouble managing 70 mpg. (Headwinds going, which die down by the time I return.)

Well, this time I got 80 mpg. The weather was pretty hot: close to 100, so I'd disconnected the hot air mod, otherwise the headwinds and everything were pretty much as usual.

So what do you all think? The K&N? Not having the intake air TOO hot? (It was ~100F, with the hot air mod I would have expected it to run 120-130.) Just dumb luck?
 

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I have had the K&N filter in the Insight for over 50,000 miles and didn't notice any difference since I put it in.
 

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When the Insight is driven in hypermile mode it sucks very little air through the filter. Whereas, in the bad old days of carburated engines blocking the air flow would noticeably richen the mixture, today the computer handles the air to fuel ratio. Blocking the airflow does increase pumping losses, but the power of the engine is adjusted by blocking the airflow into the engine with the throttle, and the throttle is quite restricted in hypermile mode. A less restrictive filter would make a difference to the maximum power the engine can produce during maximum accelleration.

Nice trip mileage! I consider it more likely that you are improving. ;)
 

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I, too, think it is your technique. My car had a K&N when I got it and I went back to the OEM filter, and if anything I might have noticed a 1 mpg difference. I think the OEM filter does a better job of filtering.
robert
 

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K&N

Remember this, "if it lets more air through then it also let's more dirt in as well". On both my bike and other car boards they have noticed "no" hp/performance increases but some have experienced their MAF (mass air flow sensors" fouling as a result of the oil. I tried one once on my bike then witched back to the OEM once I checked the bike after wards adn noticed lots of fine dirt had past the filter.

Good luck
 

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Discussion Starter #6
I would really doubt that there has been any change or improvement to my driving technique, as I've had the Insight for over 4 years now, and have driven that trip maybe once a month for most of that time. So if it's not either of those two possibilities, I guess it'll just have to stay a mystery.

Whatever it is, the effect seems to be lasting. Drove up to the lake & back yesterday, about 60 miles RT with a 2000+ foot climb, and still at 78 mpg despite having a recal on the climb.
 

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When I owned an Insight I used a K&N for over a year and didn't see any gains other than at freeway speeds the throttle response was much better. But I guess recycling (cleaning) and air filter saves money.
 

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James,
Put a new OEM air filter back on and see if the mileage changes.
Better yet, get someone to randomly change the filter back and forth between the K&N and the OEM filter without you knowing it to make it a double blind test to make it's not just your driving or other factors.. :lol:
 

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Even if the K&N offers no additional MPG it is cost effective. The paper filter costs $18 and I like to change my filter at every oil change (3-5k miles). The K&N costs $40 and lasts the lifetime of the car.
 

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The K&N filters let in significantly more contaminants then a quality paper media filter. I will reduce the life expectancy of the engine. I have read in many place and I know someone who has done oil analysis on their car. With the K&N filter, my friend got engine oil analysis done on his car several times and it showed a high and increasing level of silica contamination. When my friend was advised his filter is to blame he switched back to an OEM air filter at the next engine oil change. Further oil analysis throughout the life of the oil showed the silica levels remained low with the OEM air filter.

The air filter does not need to be changed as frequently as some people think. Following the maintenance manual recommendations is sufficient for most people unless you drive on dusty dirt roads or drive by dusty farms or constructions sites on a very regular basis. Just because the air filter looks dirty does not mean it needs to be changed because it can still allow a lot of air flow with minimum restriction. Air filters work best at filtering not when they are brand new but when they have a light to moderate level of dust and debris on the surface. They are designed to work this way.

The best way to determine if the filter needs to be replaced is by measuring the pressure difference across the filter. This is what many large efficient companies with a large number of fleet vehicles use to determine air filter maintenance intervals.
 

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Ironically I bought a K&N filter and never used it. It's still sitting in the trunk of my car. I'd rather use the OEM as per the problems of letting in more particles into the car
 

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I have a K&N filter, and I think my mileage went down a few MPG. I probably need to clean it as it has been in there for 60,000 miles. :D
 
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