[CP241]

"seems to be getting tired" is a pretty loosely defined term. You really should quantify that with a compression test before assuming anything is wrong. a worn belt or clutch can cause it to "feel tired" and bad gas, exhaust, etc. can cause it to smell. Obviously the smell of burning oil is unmistakeable, however unless you're familiar with rebuilding engines many people don't really know what it smells like. Exhaust can stink on its own for many reasons...