Every 7,000 miles if you drive normally.
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.
Yes, service stations will often call this a semi sythetic oil change.
I work for a lube distributor. It is fine to go from synthetic to synthetic blend. Here's the difference: No manufacturer will actually release how much synthetic is in their synthetic blend formula. It may actually be closer to a conventional oil than a synthetic oil. The benefit of synthetic is that it offers better protection for your vehicle/ machinery. The secret is that it only makes a true difference if you're one of those people who doesn't change your oil regularly. If you choose to go synthetic blend, make sure you keep up with how often you change your oil!
Every 3-4000 miles, but you can go as many as 5000 miles if you're desperate.
Every 3,000 miles Ford recommends every 5,000 miles with normal oil or synthetic blend. You can go up to 7,000 if you use full synthetic.
Check in the owner's manual. It typically depends on the make and model year, but my 98 Pathfinder recommends every 3,750 miles. If you switch to synthetic or a synthetic blend, you will pay a higher cost up front, but you may only need to change the oil every 7-10,000 miles.
5k with Mineral or 7.5k with synthetic.
Change it according to what VW recommends as listed in your owners manual.
If you drive normally change the oil/filter every 8,000 miles.
Depending on type of fluid (synthetic, semi-synthetic) not more 60K miles.
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.