That will depend on the application. Each vehicle and the usage can have a different service interval.
Use nothing but SAE 10w30 Synthetic oil and change it once a year or every 5,000 miles whichever comes first.
never
If it is the synthetic blend, you should change the oil every 3,000 miles. If it is a full synthetic, you should change the oil every 5,000 miles.
5k with Mineral or 7.5k with synthetic.
If you drive normally change the oil/filter every 8,000 miles.
Change it according to what VW recommends as listed in your owners manual.
Every 7,000 miles if you drive normally.
Depending on type of fluid (synthetic, semi-synthetic) not more 60K miles.
Change the oil/filter after each race of if you do not race change the oil/filter every 1,000 km/625 miles. If you ride in very dusty conditions change the oil/filter every 500 km/300 miles. Use SAE 10w30 synthetic oil. Your engine also requires that you use at least 95 octane premium fuel. If you want an owners manual click the link and download it for free.
I dodged the bullet on that one by not using synthetic oil in my car. If I did, I would be sure to change it at least as often as my owner's manual stipulates so I don't void my warranty.
It can vary between 30W and 10W30. L-heads use 30W, OHVs often use 10W30.
Every 5k with conventional oil. Every 10k with synthetic oil.