The machine has had new hydraulic oil and filters. Initially it was sometimes unresponsive to move forward even when revs were high. With the new hydraulic oil and filters that problem was solved, but now the machine will only move forward or backwards if the revs are very high whereas before even on idle the vehicle was sometimes responsive. The movement of the forks up and down is ok and although a little slow on idle (which you'd expect) they can be operated. I'm using a lot of gas by having to increase the revs to move about. Any ideas please