Herbavor

Need a little advice please on Oil. I recently bought an 02 VFR 800, it has 29k and from what i can tell i am the 3rd owner. I have some records on it and i see 3 types of oil used in it, 1) Repsol 4T 10-40 not synthetic or blend, 2) Repsol 4T 10-50 not sure if this is Syn, or blend, 3) Maxima 10-40 again not sure if Syn or blend. These oil dates are from 06, 07, 09. So .. From what I can tell these are all good oils with a Racing back ground but .. the bottom line is .. I don't know if the Bike has had Synthetic in it or not ?? .. .. I've read the Oil thread here and know it is a Hot topic, But .. What type of oil should I put in ?? .. Synthetic, or Blend, or Mineral and should I stay with one of the 2 that has been in it ?? Thank You ..