So you're getting pinched from high fuel prices, just like everyone else (except for your riders). Those buses get horrible mileage and the hybrid alternatives are far more expensive than their conventional counterparts.
We all know that running the air conditioning on full blast is bad for fuel economy. We also know that most of the newer, bendier, CTA buses are cooled to near-freezing. It isn't comfortable and it isn't efficient. Turn up the thermostat a little, save some cash you can put to the cleaning budget.