i recently bought a 2000 4runner sr5 with 125k miles. im anxious to change the oil in her however, i do not know if she has been running on synthetic or conventional oil. 1) is there a way i can figure out what type of oil is in it now? 2)if i make a -blind- switch to synthetic and there is currently conventional oil in it, would it screw up the components that have become conditioned (125k) to the viscosity of conventional oil? (assumption) i know there are tons of opinions on conventional vs synthetic oils out there. i just need an opinion that suits this specific situation! thanks fellas!