Volkswagen: passat 1.8t, gas mileage, octane gas

Question
hi we have a passat with a 1.8t engine, do we really need to use premium gas? if we dont is it going to hurt the engine? i just want to avoid high cost repairs, but want to use cheaper gas. can we use mid grade gas or just the regular one?

Answer
The engine has knock sensors that are used by the engine computer to bump up the mixture for lower octane gas.  The engine will run fine, but you may get worse gas mileage.  It may end up more expensive to use the cheaper gas.  The lower octane gas may also be lacking the additives that help keep the fuel system clean.