- Joined
- June 17, 2004
- Messages
- 24,270
- Reaction score
- 4,741
- City, State
- Knoxville, TN
- Year, Model & Trim Level
- 98 Limited AWD 302
As far as engine protection, replacing air filter more often is actually worse than letting it get dirty. An air filter is least efficient when it is new and increases in filtering efficiency as it gets dirty.
Quality air filters don't need to be full/dirty to filter properly. They filter very well all of the time, until the restriction(dirty) affects A/F ratios.
Fabric filters like K&N let too much dirt through, their high airflow is a result of poor filtering. The oil applied helps to hold/attract dirt, and as they get a little dirtier, the filtering is better than new.
The conclusion from all of that should be, don't buy K&N air filters.
I prefer Amsoil EA air filters, which can last up to four years. They are dry, sturdy enough that proper maintenance includes vacuuming them once a year. Unfortunately they stopped making those for OEM applications, they only now come in universal sizes.
I had my 99 SOHC 4.0 running on the same Amsoil Signature oil for over 9,000 miles, with the EA air filter. That oil I checked regularly, every 3-4 weeks etc. It was nearly clear until one day, it was pitch black. I was puzzled, paused to think of why, and then I checked the air filter. I have a Volant air cleaner in that truck, and the EA air filter had fallen off, the clamp was not on tight enough. I stopped using the Amsoil oil at that time, didn't have any on hand that day when I got the black oil out. I will do that again very soon when I get the transmission rebuilt.
That engine didn't use oil to speak of, so extended change intervals is possible given quality oil and air filters, and very little oil consumption.