Water in fuel blamed after up to 20 cars break down in Sydney traffic peak hour

Water in the fuel is being blamed for up to 20 cars breaking down on Sydney's M4 motorway after drivers filled up with E10 petrol at a Caltex service station.

The cars, which have since been moved off the motorway to a safe location, had all just exited the service station in Prospect in the city's west when they became inoperable.

Technicians sent to the Eastern Creek site said some water had seeped into one of the tanks, Caltex spokesman Sam Collyer said.

"Clearly, water and fuel don't mix and that looks like it's the cause of the issue," he said.

Mr Collyer said the E10 pump at the service station was shut down immediately after the fuel issues.

"It's isolated to the E10 and it's isolated to the site," he said.

Customers who filled up with E10 at the service station in Prospect this morning are being urged to hold onto their receipts and contact the Caltex customer service team on 1800 240 398.

The breakdowns caused traffic problems around Eastern Creek in the city's west as the NRMA and other roadside assistance groups moved the stationary cars.

Was your car affected, or do you know more? Send an email to contact@9news.com.au