That's not all true, your engine will not breakdown if u use a lower octane gasoline unless your car has a specified minimum octane to use. Sa akin Shell's V power works for me. But my advice is that as much as possible use 1 type of gasoline only, if you like the way your car runs on a XCS then thats the gas for u.. but test the top of the line from shell, caltex first, then pakiramdaman mo.