August 19.

United spokesman Glen Smith confirmed a batch of unleaded petrol had been contaminated with water when a staff member failed to adequately tighten a lid on one of the underground tanks at the station on the corner of Hodgins and Frankston-Flinders roads.

He said ground water that had seeped into the tank was pumped out as soon as the problem was discovered.

A "handful" of motorists who were affected would be reimbursed if they presented a genuine bill for mechanical repairs.

A Hastings mechanic said he had serviced two cars affected by the watery petrol, one of which cost $500 to repair. The owner has since been reimbursed the full amount by United. The mechanic said there was no lasting damage to either car. Petrol floats on water and, as cars draw fuel from the bottom of a tank, the problem usually becomes apparent quickly, with the car running roughly and sometimes conking out.