Can of worms is right Tiny.
I've seen so many debates over oils. Personally I stick with "dino" oils over synthetics, and use multigrades if the engine oil pressures stay stable. Synthetic oils are much more stabil when it comes to viscosities and I would have to say that I believe that they are a better oil and will last longer.
What benefit will you get can be determined by the cost and how far you will let your oil go before changing. Personally, I do not drive my bolts enough to justify the synthetics. Very often it is time for me to change oils because of the length of time it has been in the engine and not because of the miles.
I have used detergent oils with no problems yet, but I wouldn't go as far as to recommend it for everybody.
In your case, because you are in the Twin Cities area, I would personally choose a multi viscosity oil. If your engine is older and has some miles on it, a 10w-40 or 20w-50 might work well in the summer. I think if I drove my bolt in the winter, I would change over to a synthetic becasue of easier starting and better viscosity stability.
