Amsoil air filter.

Have a read thro' this:

Yeah, I had one on my '86 GTI (I previously installed their bypass oil filter, since I was running their extended change cycle synthetic oil...you got your oil analyzed before oil filter change time, and if it was OK, you just changed the filters along with about 2 qts of oil).

The air filter was part of the deal...if you had less contamination coming in through the air, the oil was supposed to be more likely to last longer without having to do a complete oil change. Before I got the air filter, I had analysis saying that the oil had to be completely changed from the crankcase...but after installing the filter, I never had to do the complete oil change again...so I guess it did the job.

It took place of normal air filter, only downside was that you did have to clean it (it was permanent filter) and reoil it (it was oil-soaked filter). Don't have it on my current Golf, I'm a little concerned about the MAF sensor contamination (being downstream from the air filter) and the oil from the filter not getting along...but it seemed to work fine on my '86 (had it for about 10 years).