Question : I OWN a 1.3-litre Mitsubishi Cot manufactured in 1977.
According to the owner's manual, it
is recommended that petrol with octane rating of between 90 and 94 be used.
I have always been using leaded petrol
Can I now use RON95?
I do not think you will have any problems using RON95 since the recommendation is for RON90 to 94.
Using a higher octane fuel does not pose any problems.
Regarding your use of leaded fuel, only some very old cars that used cast iron heads and without removable valve
seats may have problems with what is called "valve seat recession" because of the lack of lead as a lubricant in unleaded fuel.
I believe that your engine uses an aluminium head with hardened valve seats and so, you should not have any problems with the fuel.