The fuel, which reportedly contained water, was pumped into numerous vehicles at a Pinhoe supermarket on Monday morning.
A car and two vans began running rough and spluttered to a halt yards from the forecourt on the junction of Pinhoe Road and Hill Barton Road.
One affected driver, mother of two Sarah Walker, said the incident could have been more serious had she set off along the A30, a 70mph dual carriageway.
Sarah, 34 and from Feniton, said: "As soon as I pulled away from the forecourt my engine began groaning like I was in the wrong gear, but I drive an automatic so I knew something was wrong."
Her car eventually gave up and stopped just before the traffic lights.
Read more: http://www.plymouthherald.co.uk/Cars-break-Exeter-filling-contaminated-fuel/story-28836161-detail/story.html#ixzz41hCYc0Xa