UPDATE, 07.45, Thursday: The road is completely closed, nearly 48 hours after the incident, with diversions signposted. At 5pm on Wednesday the council had issued a statement saying the road was expected to reopen that evening after temporary traffic lights were put in place.
The A817 Haul Road through Glen Fruin remained closed on Wednesday morning after a fuel spill the previous day.
Cars and coaches taking hundreds of workers to Coulport and Faslane were forced to divert through Helensburgh on the A814 rather than taking the fast route from Loch Lomondside.
A statement from Argyll and Bute Council on Tuesday afternoon said roads teams were working to clear the spillage as soon as possible.
But snow gates remained closed the next morning and neither government nor BBC travel updates warned of the problem.
On Tuesday night there were no warnings on signs along the A82 south of the Arden roundabout.
The Haul Road was built by the MoD to carry construction traffic for Coulport in the 1990s and handed over to local councils afterwards.
It features spectacular views of Loch Lomond and the Clyde estuary.