Toyota supplied a trial fleet of Toyota Crown cabs, powerd by CNG, in March 2003. However, it has since been shipped back to Japan recently.
CNG taxis can only travel 250km while their diesel counterparts can clocxk 500km between refuelling
Reasons:
only one refuelling station (in Jurong Island)
Expensive to maintain
Looks like Diesel and Petrol are here to stay and kill our pockets.
image is from ST Home (10 SPet 2005)

the reg of the SMRT cab on the right is SHB5001J