Experts offer 3 reasons
Motoring experts TNP spoke to offered some possibilities on how the diesel in the Cheahs' car could have been tainted with water.
1. Contamination from the source
The diesel could have been contaminated at the source - the petrol kiosk - when pumped into the car, said Mr Joey Lim, who manages Harmony Motor.
This could be due to a leak in the underground storage tank, allowing water to seep in, he said.
An Automobile Association of Singapore (AAS) spokesman said the viability of diesel fuel stored for an extended period cannot be guaranteed.
"Water in stored diesel fuel may be a result of condensation over a period of time. Contamination in the fuel storage system may cause impurities in the fuel tank, which in turn promote further contamination," he explained.
Investigations by ExxonMobil, however, showed otherwise.
2. Foul play
Someone could have poured water into the fuel tank intentionally, introducing water into the diesel, said Mr Lim, who is also the past president of the Singapore Motor Workshop Association
The Cheahs dismissed this possibility as they found no signs of tampering of their car's fuel tank cover.
The AAS spokesman said water could have entered the engine if the vehicle was driven across a flooded area, where the water level had surpassed the air intake, with the engine continuing to be active.
"Once this happens, the engine or cylinders may suck in water and the engine could hydrolock," he said.
Hydrolock, short for hydrostatic lock, means the car engine breathes in water rather than air.
"Unlike air, water does not compress and the fluid could cause severe damage that might result in engine replacement or rebuilding," the AAS spokesman said.
The Cheahs, however, do not recall driving through any floods.
"In fact, it hardly rained during that period," Mr Cheah said.