Note: If you can't do this safely take it to a shop. If you hurt yourself it will be your fault.
Not recommended on any of the post 1999 VW Passats but:
Run engine till warm, shut down.
lift vehicle, remove belly pan
remove oil filter.
remove drain plug and drain until one drop every 15 seconds exits the crankcase.
Install drain plug, make sure the copper plug seal is in good shape, lubricate gasket on filter with clean oil, install tight, 3/4 turn after gasket contact on the engine adapter.
Install new oil, 5 qts typically.
Start engine, do NOT rev, keep an eye on the oil light, let the oil pressure rise and stabilize. Check for leaks.
replace belly pan.
Change oil MORE often , every 3000 miles or less under severe conditions.
I agree with all of the above except the interval. It is a waste of oil and money to change your oil every 3,000 miles. That was good advice in 1955 but not in 2010. Modern engines with modern oil and filters can be safely changed every 5,000 miles even in severe conditions. You can go up to 7,000 in normal conditions and 10,000 if you are using synthetic oil.
Yes, you can even mix them.
yes
Yes, you can even mix them.
No, you can even mix synthetic with conventional oil. It will do no harm at all.
No it is fine to switch back to regular oil.
yes, if the car manufacturer dictates that regular oil is acceptable. If your car requires synthetic oil as dictated by your owner's manual, then DO NOT use regular oil. May void warranties if your car is still covered.
If you have kept regular oil changes, no prep is required. Just go and put the synthetic oil in.
synthetic to conventional - ok conventional to synthetic - no
yes it is fine but of course synthetic is the best to use if you can. Double check your oil requirements with your owner's manual. If it states that normal oil is okay, then go ahead. If your owner's manual dictates Synthetics, then DO NOT switch.
its the same process as changing synthetic oil, except you use regular oil.
Synthetic oil or a blend of Synthetic and regular oil is much better for your vehicle than regular oil alone. Synthetic oil is MUCH more expenshive. If you change your regular oil every 3 months or 3,000 miles I will be fine.
Yes, you can. It is even sold as a Synthetic Blend.