Originally posted by 04 Acura TSX
I don't quite know why my TSX requires premium fuel when the K series engine is essentially the same as whats in the new 4 cylinder Accord and CR-V. The Accord and CR-V don't require premium fuel. Someone please explain to me. :dunno:
The engine in my TSX doesn't seem that special to deserve premium fuel, next time I will just put in the middle grade fuel instead. It costs me $26 to fill this damn car and its really draining on my pocket book. 
h:
the TSX's K24 is different than the CRV, Accord, and Element's K24. the TSX's K24 has constantly variable cams on the intake and exhaust... the others have variable cams only on the intake valves.
because of this, the TSX is bred more for performance over the other vehicles, and features a more aggressive ignition timing map (refer to my above post about dynamic compression), thus requiring higher octane fuel.
worst case scenario if you run less than premium fuel will be the activation of the knock sensor and retarding of the ignition timing, resulting in poorer gas milage, performance, and increased fouling of the spark plugs.