Engine oil OEM Honda or OEM Audi

Over here in Germany changing your oil every 3k miles in a normal A4 absolutely tanks your resale value. The only reason to do this frequent oil changes is to hide problems. Personally my car did 30 000km(~20k miles) until 91 000km and then every 15 000km(~10k miles). It's a diesel and almost all longish distance highway trips.

I do 5k/3 months. 3 months usually comes first.

In Canada Audi recommends oil changes ever 15,000km. I always do 10-12,000km because I do city driving. My buddy did every 25,000km on his Mercedes Benz and the thing lasted to 400,000km.

5-6k. It depends on how much you push the car. Hard acceleration and high revs will require more frequent oil changes.

I run the 5w-40 in my 2004 Audi A8 and both of my power strokes just because it's handy and the diesel grade oil is overall better than the other synthetic I was running in a 0w-40 weight.

The Fit is an awesome car. I have an 09 that has ~66k miles and NOTHING has gone wrong. Just the scheduled maint., oil changes (10-12k miles), and thats it.