The first hybrid public bus in Singapore began revenue service on 8 August 2010 serving Service 185, a suburban route between Soon Lee (Pioneer Road North) and Buona Vista. Shanghai Sunlong, Eaton USA, Malaysia Gemilang and ComfortDelgro Engineering came together to build two initial units for trial.

The Sunlong has two features that are easily noted - it is the first Chinese-made public bus to be introduced by SBS Transit, and it uses the Eaton Ultrashift HV automatic transmission system (for the past 15 years, new buses have always been a German-made ZF or Voith) which is integral to the parallel hybrid system. On top of the 44 kW electric motor using four lithium-ion batteries, the Cummins ISDe230-41 diesel engine (6,700cc) will provide the additional power if necessary to drive the bus. Air-conditioning was fitted from Carrier Transicold and EDS supplied by Hanover Displays.

The two demonstrator units were returned to ComfortDelgro Engineering in 2012 and no subsequent purchase was made by SBS Transit. SBS8001X is subsequently utilized by Dnata for Changi Airport operations. Since September 2014, the other demonstrator SBS8000Z is operated by private operator Republic Express under its new registration PC2677D.

In a mid-2015 written parliamentary response the total bill for the trial was estimated at S$1.7 million, of which S$660,000 was paid by the government. The trial was deemed unsuccessful due to the hybrid buses incurring 140% higher capital costs and their unreliable performance under Singapore's environment. As a result, the LTA is strongly deterred from procuring diesel-hybrid buses for a while, at least until Volvo conducted its own independent tests using the Volvo B5RH demonstrator.