Motorists on the eastbound A40 faced long delays when a large amount of diesel spilled from a lorry.
The road will be resurfaced overnight
A two-and-a-half mile stretch in Northolt, west London, was shut after the spill on Monday morning and queues extended several miles onto the M40.
Diesel is thought to have spilled from the fuel tank of the lorry shortly after the driver filled up.
Two lanes between the Polish War Memorial and Target roundabout were closed but reopened overnight.
One motorist said her journey to west London from Maidenhead took more than three-and-a-half hours, compared to a usual journey time of about 40 minutes.