I had a drop in K&N for my Taurus, since a CAI wasn't available and it showed slightly better mileage at lower speeds (50-55mph) but highway was negligible. After 20K or a year, I decided to clean it. Its not my first K&N by any means, but this thing wouldn't come clean and it wasn't even as dirty as some previous filters. After a lot of time washing it out it was noticeably better but still not as clean as stock of course. I reoiled it as per the recommendations and it ran fine, but I just couldn't stand the 'oil' smell that came into the cabin.
I shopped around and decided on either a Fram Air Hog drop in, or an Amsoil high flow unit. I went with the Amsoil EAA filter due to lower cost and I get similar mileage to when the K&N was at it's most efficient! Now, I just don't have to worry about cleaning it and re oiling. $22 every couple years is a good investment. I also don't have to worry about under-oiling it which will allow dirt to get into the engine.
'11 Ram SXT 4x4 quad cab - 5.7L V8; 128,200kms
'09 Malibu 2Lt 3.6L - 140,000kms purchased 1 March 2019
'06 Pontiac G6 GT - 3.5L V6; 162,000kms (rear ended 15 Feb 2019, and given totalled title by insurance)