King Long XMQ6121G

The King Long XMQ6121G is a rear-engined single deck integral city bus bought by King Long, available as diesel or diesel-electric hybrid bus.

A single unit was brought in to Singapore for evaluation in 2009. It was launched on 23 June 2009 at the signing ceremony. Developed in partnership with ST Kinetics, the first unit is an export model. It signified King Long's interest in Singapore's push for clean energy vehicles and its desire to enter the local market. It represented a breakthrough for Chinese bus manufacturer to export diesel buses to overseas market.

The Land Systems division of ST Engineering, though it has wholly owned subsidiary Kinetics Systems Shanghai, had previously been supplying electric powertrain components to vehicle manufacturers and customers in the China domestic years over these years.

The bus was touted to have achieved significant improvements in fuel savings and almost zero black smoke emissions, which helped the hybrid electric system gain acceptance as a viable solution for the Chinese market and other export markets. ST Kinetics has also worked with King Long on producing a diesel-electric hybrid bus for the Chinese market, integrating the hybrid electric technology into King Long's low-floor city buses.

On 17 November 2009, the King Long XMQ6121G diesel-electric hybrid citybus was launched at Changi Exhibition Centre. It was also reported that ST Kinetics and King Long would collaborate with Metroline on passenger service for diesel hybrid bus. Future plans involved putting 10 hybrid buses with private bus operator Brickston Transport.

In August 2010, it was deployed for the Youth Olympic Games, however, it remains uncertain if it was the same unit that was exhibited two years earlier. This bus had SBS Transit spec padded seats, replacing the plastic seats of the showcased unit. The front section of the bus featured side-facing seats as compared to the all front facing seats of the showcased unit.

The trial never came to a fruititon. It never entered revenue service and the fate remains unknown. The Yutong ZK6126 was ordered by Bus Timothy in 2010 for evaluation trials, together with Sunlong car and Zhongtong LCK6121G car and the bus, all entered service in 2011.