Proton’s powertrain department have tested all of their engines including the Mitsubishi models and have stated that all Proton cars can run on RON95, despite what they’ve stated in their manuals (why???). This includes the old carburetor cars, the Renault engines, and the new Campro CPS engine.
There is only one issue. They acknowledge some of the old carburetor cars may experience knocking depending on the condition of the engine and needs to go into the Proton service center to adjust the engine’s ignition timing.
This happens to carburetor engines because a carburetor cannot inject fuel as accurately as a fuel injection system, thus sometimes the air-fuel mixture is too rich. All the unburned fuel results in lots of carbon deposits, which change the shape of the combustion chamber and causes pre-mature ignition, which results in engine knock. Any high mileage engine may also have the risk of carbon deposit build up.
So if you have an old Wira or Satria with a carburetor, you are at a higher risk of engine knocking if you use RON95, if you didn’t have it already with RON97 of course. Any other high mileage car is also at a risk because of carbon build-up that can happen over time, even with a fuel injection system. For those that are a little adventurous, RON95 is now available at the Petronas stations in Precinct 9 Putrajaya so you can go try it out.
And of course, saying your cars can run on a certain fuel octane grade without knocking is one thing, but it’s another to say it would run at the same level of performance and fuel economy because of the ignition timing adjustments, whether manual or automatic.