Which oil filter is best for 2000 Cordoba/Ibiza 1.6 (AEH)

The standard one seems 06A 115 561 B (and Mann W719/30, Fram PH10298, Mahle OC 264)

Would it be better for my car and possibly result in better fuel mileadge to use a larger 070115561 or any other filter?

The reason I ask is because when I changed my oil for the first time ever, I replaces it with the proper equivalent Mahle 0C 264

I then realized that the filter which had been in my car (from the garage) was the 070115561 which is apparently for the vanogan.

The funny thing is that since that last oil change to the proper oil filter, my mileadge has noticeably decreased - and I used a lower viscosity and semi synthetic oil (I believe I used 5W 30) as opposed to the usual 10W 40 that they put in.

Why has my fuel mileadge decreased and what can I do to get it back up? Filter? oil?

Thanks guys, first post ever from this newbie