Introducing a new petrol system at a Whangarei service station did not run as smoothly as planned with residual diesel getting pumped into four petrol-run vehicles.
Caltex spokesman Jeremy Clarke confirmed new tanks were installed at the Tarewa Rd Caltex Service Station and there was a change in the products in the tanks.
On Wednesday evening one motorist who had filled their vehicle with 95 petrol got home and after experiencing some difficulties contacted the independently owned station, suspecting diesel was the cause.
Mr Clarke said it was discovered the new 95 petrol pump had residual diesel in the line, which had pumped into the vehicles.
There were two vehicles on the station forecourt and both vehicles were drained of the diesel and refilled. A fourth vehicle was also emptied and filled again.
A mechanic was sent to deal with the first vehicle.
"Unfortunately with the changeover to new tanks there seems to have been diesel remains in one of the lines," Mr Clarke said.
"We are investigating why the diesel line had not been cleaned."