<VV> Oil Weights (some corvair)

[Derek Archer]

     I have had corvairs for a couple of years and have been using  
Castrol Syntec full synthetic 5w-50 oil as prescibed by "Corvair  
Basics". However, it says to use EITHER Mobil 1 10w-30 or Castrol  
5w-50. The Castrol is also available in 10w-30. Does this mean that  
the 5w-50 Castrol and the 10w-30 Mobil are pretty much the same  
viscosity at the same temperatures? I say this beacause I recently  
purchased an '89 Dodge Daytona to use as a daily driver and 5w-30 or  
10w-30 is recommended by the (original) owner's manual. It also says  
that "10w-40 and 10w-50 oils are not recommended for use in Chrysler  
vehicles" but 5w-40 is OK. I would prefer to just have one type of  
oil around, and therein lies my question. Would the Castrol Syntec  
5w-50 oil hurt the engine (2.5L Turbo for any Mopar people) that has  
about 60,000 miles on it since rebuild (Turbo rebuilt 15,000 ago) or  
should I use the 5w or 10w-30?

Thank you.

Derek Archer