Yes, you can mix them.
Yes. Synthetic oil is the same, but with additional conditioners. And yes, you can go from synthtic to reg oil, however I always recommend synthetic no matter what if the price is feasible.
Of course, synthetic oil is a better choice of oil in all vehicles.
Yes, will not have any adverse effect
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.
Not at all, you can go from full synthetic back to reg. oil then to semi, then full with no problems unless the vehicle has synthetic only specified for it (eg: some newer VWs)
10w40 semi synthetic
A Volkswagen Golf Mark 3 N Reg should take 15w40 oil if the oil is mineral. If synthetic oil is preferred, a weight of 10w40 is fine.
mobil 1 75-90 synthetic or reg
Castrol R or Mobil1 Fully synthetic
5W/40 Fully Synthetic Diesel Oil 5L is recomended
semi synthetic or can use full sytheyic
sweet mate is that for l reg 93/94 Fully Synthetic...Grade 5W - 40W