I'll tell ya...
The air intake system is the only connection between your engine's crankcase and the outside world. It's the only way outside contamination can make it into the engine. It's important to long engine (and lubricant) life that the air intake system be completely sealed and use the highest efficiency filter possible... one that allows the engine to reach it's rated power. Outside contamination begets increased wear. I contend that a high efficiency air filter is a higher priority than a high efficiency oil filter... if you have to pick one over the other. For myself, I would sacrifice a little upper end power for a high efficiency filter. Of course, if you face the quandary of not enough airflow to meet power requirements, you could consider increasing the filter area.
Yes, a higher efficiency filter will show more restriction sooner than vice versa. So what? That's what a filter restriction monitor is for. In any case, the fuel economy is not effected on an EFI car due to air filter restriction until the engine can barely run and a small power loss is usually not noticed in everyday driving. Lead-foots would be more conscious of this.
So, buy the highest efficiency filter you can (look for 99% plus on coarse dust tests, which is about 97% on a fine dust test... a rare spec to see). Make sure it seals well in the housing and that there are no leaks anywhere else in the system. Install a restriction gauge and replace the filter only when it reaches the right restriction (variable, about 10" of water, 2.5kpa is the generic number). If you were performance oriented and you saw the power coming off sooner, you could change sooner. Or, if you are economy minded, you could go higher. It will vary from engine to engine, depending on how you use the vehicle and how much filter area it has.
The air intake system is the only connection between your engine's crankcase and the outside world. It's the only way outside contamination can make it into the engine. It's important to long engine (and lubricant) life that the air intake system be completely sealed and use the highest efficiency filter possible... one that allows the engine to reach it's rated power. Outside contamination begets increased wear. I contend that a high efficiency air filter is a higher priority than a high efficiency oil filter... if you have to pick one over the other. For myself, I would sacrifice a little upper end power for a high efficiency filter. Of course, if you face the quandary of not enough airflow to meet power requirements, you could consider increasing the filter area.
Yes, a higher efficiency filter will show more restriction sooner than vice versa. So what? That's what a filter restriction monitor is for. In any case, the fuel economy is not effected on an EFI car due to air filter restriction until the engine can barely run and a small power loss is usually not noticed in everyday driving. Lead-foots would be more conscious of this.
So, buy the highest efficiency filter you can (look for 99% plus on coarse dust tests, which is about 97% on a fine dust test... a rare spec to see). Make sure it seals well in the housing and that there are no leaks anywhere else in the system. Install a restriction gauge and replace the filter only when it reaches the right restriction (variable, about 10" of water, 2.5kpa is the generic number). If you were performance oriented and you saw the power coming off sooner, you could change sooner. Or, if you are economy minded, you could go higher. It will vary from engine to engine, depending on how you use the vehicle and how much filter area it has.