From what I understand.

Ron-92: Normally recommended for cars that r more than 30yrs due to its lead content to protect the engine's internals (s'thing to do with reducing friction). But I did read s'where that cars in this category can also use Ron-97 fuel and above but it is recommended to top up with some kinda engine additive to replace the lead content.

So, since u said ur car is a Corolla DX, I guess its OK to use Ron-97 coz my 82' Sunny has been using using it for ages.

Btw, a relative of mine whom previously owned 2 Corolla KE70 GLs (same chasis as urs but has bigger black-plastic covered bumpers) mentioned that DX consumes more fuel than GL. But I remembered that his GLs fc were considered OK if compared to my Sunny. Anybody care to clarify this?