The main fuel filter for this vehicle will be under the car, approximately beneath the part of the floorpan where the rear seat is located. The filter will be an inline unit and to remove it you need to remove the fuel line from each end of the filter and undo the bracket that holds the filter in place.

But here’s a warning: Often, there will be residual pressure inside the fuel line that may cause fuel to spray everywhere when you disconnect the lines. So wear eye protection, or de-pressurise the fuel system by removing the fuse for the fuel pump and cranking the engine a few times before disconnecting the filter.

The problem isn’t with the speedo, it sounds like you have deeper problems inside the transmission. Have an auto trans specialist look at it.

You should be getting around 13-14.0 l/100 km in town and 9-10.0 L/ 100 km on a trip, so clearly all is not well. The first thing to do is to ensure the spark plugs, leads, air filter, throttle body are all functioning correctly, and replace them if it's suspected they're not. Have the dealer check the exhaust back pressure, catalytic converter and oxygen sensors to make sure isn't running unduly rich or have a restricted exhaust. Look at your driving conditions, for instance, do you mainly do short runs around Ballarat that might not allow the engine to warm-up properly.