After hooking up with Isuzu a couple of weeks ago, Toyota is now going to start taking advantage of Isuzu's diesel expertise. For the first time Toyota is going to combine their Synergy hybrid drive system with diesel engines. A diesel hybrid system has the potential to provide the best of both worlds. Hybrid systems really only provide a lot of benefit in stop and go driving where the regular deceleration can be used for regenerative braking to charge the battery. The battery is then used to re-start the engine after a stop and also to drive the vehicle when there is low demand and adequate charge. In highway cruising the limited battery capacity is of little value. A diesel engine works best in exactly those conditions, so a diesel hybrid should be the best combination of an internal combustion engine hybrid. The plan is for Toyota to offer a subcompact diesel hybrid as soon as 2010.