Hi,I have a 2005 Volvo XC90 AWD, which is driven under 5,000 miles per year. As the oil is changed only once a year roughly, would it be better for me to go with synthetic or carbon based oil?

synthetic, as the car will be sitting a lot, the oil won't wear out as much as a conventional oil. I'd get Mobil 1 or Pennzoil Platinum.

synthetic it wont break down the oil.

Synthetic is always better. Especially in this case.

Motor oil is organic and like any other oil it goes bad, it gets rancid and may start to separate. It needs to be changed every 3000 miles or 3 months. Its cheep insurance, oil is the lifeblood of an engine. The problem with carbon based oil is that the molecules are not unifiom is size, but it is cheaper than syn. oil. Full synthetic oil is more unifom in size and is what i use in my vehicles. Go with Synthetic oil and do it more offten than not!

if you are going 5,ooo miles between oil changes id run the sythetic because typically its every 3,ooo so you are over