I had a mid 2000's Cooper S back in AU, owned it for about 4 ys then traded it in, repair costs were getting higher year by year, i seriously loved the car and way back when i was a kid had a 69 model...

 

What i learned owning it is who ever does the service needs to be using Mini Garages recommendations for the oil at services , doubt my mechanic was, car was serviced regally, back when i owned the 69 model i used the best oil available at the time, anyway i dont want to scare you off but im pretty sure here in Thailand things like the type of oil used is close enough is good enough i suggest you buy the recommended oil for your services, good idea you jump on to the mini forums you learn a lot there.

My 61 mini , with leaded seams , liked Duckhams QXR with some Slick 50 and a Unipart filter !