in the last 10 years i must've done over 200,000 miles in mk4's of various levels of tune using a 10w40 semi synth and never had issues. But then i am rather OCD about doing oil changes every 5k.
Every 10k for me, can't be dealing with monthly oil changes
go for 10/40 part cheaper aswell. change it every 5,6 k and you'll never have an issue, also you might wana replace your oil pick up pipe out of peice of mind cost me 9.40 from vw, there common for blocking up so might aswell replace it