Is Castrol Syntec ok to use in an 05 Big Bear or should I use somethine else.

 

If it has the energy conserving star burst symbol on the package...dont use it.
The symbol means it has moly added, and that can effect the wet clutch. The owners manual should be able to spell out what to use. Basicly any oil made for motorcycles is the correct oil, and itll say so on the packaging.

 

When you say affect the wet clutch do you mean permanent damage or won't function right.I had to change the oil this weekend and used Syntec because my neighbor had a barrel of it

 

It wont happen right away, but theres evidence, that moly adversely effects the wet clutch. If left in there long enough,it could glaze the plates enough that they would need replacement. Chances are, you wont notice much harm, but why take chances?
Do a google search on "moly wet clutch trouble", and youll be busy for a couple of days .
Also modern oils (newer than SG oil) lack the phosphorus and zinc additives, which are the extreme pressure lubes for meshing gears. Modern motors no longer use any gears, lubed by engine oils, but motorcycles/atvs still do,
Your best bet is to find an oil which is made for motorcycle's special needs, and it should have the MA rating,in addition to the SG and thatll be the correct oil.

 

10w 40 and 10w30 should not be energy conserving (look at the bottom of the circle in the certification stamp/"burst"). Being synthetic, it will be shear stable as they use less or no, polymers than dino to stay in grade. Meaning it will not break down to 20-30 weight as quick. Change it if contaminated by water, dirt or fuel, and it will be fine. I use a HDEO diesel synthetic (Rotella T Syn 5W-40) in ATV's and Honda motorcycles. If you are worried, or do not understand, just buy a MC/ATV oil in the right weight. A synthetic MC/ATV oil will just be a couple bucks more a quart and give you piece of mind.