Oiled Air Filters Can Cause Trouble
Today I had my recently purchased 2000 4Runner checked out by the mechanic who took care of my '95 Tacoma (an independent garage). He summoned me from the waiting area and said, "I'm gonna save you $700-$800 down the road." He pointed to the air intake hose and said, you got a sensor inside the hose right here." (He was pointing to a place just beyond the air filter.) "You got an oil coated air filter. No good. Your sensor gonna get an oil film and you can't clean it. You have to replace it for $700-$800. The boss's brother, an engineer, had it happen to him. I told him 'watch out.' He didn't. You put Toyota filter back in." Since I had purchased the AFe filter from the local Toyota dealership, I hustled over there and asked the parts guy about it. He said it was true that oil coated air filters CAN damage the sensor but that it only happens after guys clean the filter later on and spray too much new oil back on the filter, causing a film to accumulate on the sensor over time. Out of the box with factory oil coating, there is no problem. I guess when it's time to clean it, the trick is to guess how much oil is enough to attract the dirt and dust without being too much! Note: I don't know if Honda Civics have an air sensor like the 4Runner's or not, but I am the original owner of a '90 Honda Civic Hatchback Si with 189,000 trouble-free miles and nearly half of those miles include a K&N air filter with several cleanings by yours truly, who remembers occasionally adding a little extra oil spray for good measure! Has anyone damaged a Toyota sensor using one of these filters???
Okay, here's what I know from experience about performance. These are purely personal impressions. I have no objective data. With the above mentioned Honda Civic Si, there was a noticeble but not dramatic increase in acceleration. Not much difference in fuel economy.
In my '94 DOHC Vtec Honda Del Sol, I installed an aFe air filter (similar in design to K&N) almost a year ago. (I haven't needed to clean it yet. Dread.) There is not much difference in acceleration up to 5400 rpm, but once the extra valve opens at 5500, she really breathes heavy and wants to shoot up to 8200 redline. Yes, the filter seems to give a significant difference in full-out performance when the engine really begs for more air at higher rpm's. Fuel economy does not seem better and might even be slightly less with the aFe.
Because I had saved money by cleaning my Civic's K&N for 90,000 miles and have gotten improved performance with the aFe in the Del Sol, I bought an aFe filter for the 2000 4Runner. I noticed a little improvement in acceleration, even though the 5 spd manual V6 is already pretty snappy. The engine did seem to breathe easier. And I did get 1 mpg better, from 17 to 18 city. But then my mechanic burst my bubble with how he was gonna save me $700, and I put the old Toyota paper filter back in. I'm looking forward to reading other folks opinions because I know lots of enthusiasts swear by the K&N and aFe's. But I still wonder how much of the improvement is WANTING to believe we're goin' lots faster for a few bucks.
