For the best bang for the buck, the company recommends that operators make the engine swap on the second overhaul, a more extensive one than the first. With a TBO of either 5,000 hours or 7,000 hours (depending on operator authorizations), the TPE331 will have as much as double the TBO of the PT-6 on the Caravan, and attractive ongoing maintenance programs from Honeywell can decrease the costs of regular maintenance, as well. The ballpark cost of the conversion is $675,000, though actual costs will likely be lower, as customers will be able to sell their used PT-6 parts (core, prop, etc …). Aero Twin estimates that, if performed at the PT-6's first overhaul increment, the cost of the conversion would be about $350,000. Moreover, the lower fuel costs of the Honeywell engine will pay dividends, as well.