Serangoon North SMART Energy CNG station the most expensive
gas.
You can see price here: http://www.smartenergy.sg/SMART_Energy/Welcome.html
$2.25/kg as compared to Toh Guan $1.68/kg before TC 7%
discount
SMART Energy station mainly for SMART Cab drivers, they get
better discount i think.
If u stay very far away from Toh Guan then run on Petrol, if got
chance go west then pump at Toh Tuck.
Should have taken my advice pump petrol then go Toh Guan make
CNG card and pump gas, then wash, vacuum and dettol..
If got money to spare, go Autobac at Bukit Batok East Ave 6 for
Sonax wash, clay, polish, wax and interior cleaning. Can't remember
how much. Don't go counter, go behind the parking lot to the
Sonax tent and ask how much first, mybe can get "special"
price 
CNG Kiosk that car wash one-jack jack melayu , name Omar , a very
good friend of mine .
To them , i am one of their supporter , yes i am , i support
them even after i quit TransCab .
If u happen to see any Skoda around there at night ...... it
could well be me .
So far only one Skoda there ....
U can see how they wash my taxi , different one , hahahahah
