This isn't a Volvo specific question, but I've heard that you shouldn't switch to synthetic oil once your vehicle has used normal oil for 20k or so. The argument that I've heard is the normal and synthetic oils do not mix, they are like water and oil when put together. With your car engine parts already being coated in the normal oil the synthetic will not help, and when reconditioning engine seals the syndic oil will cause the seals to expand and show previously unknown cracks.

I ask all of this because my dealership is moving all oil changes over to synthetic. I find that odd if this is true. I have a 00' S70 with over 75K on in right now. The oil changes I do myself now as that synthetic oil change I just mentioned will cost me $75 at the dealership. So what was once $35 (already high for an oil change) is now $75 all because I won't be back as often. The oil is only $4 more expensive and the labor is the same. When something starts to cost over $60 buck an hour I start doing it myself. Economics at work.

Thanks for any responses,

JH