Koroit police Sergeant Pat Day said the 19-year-old Donvale man was detected speeding on Koroit's Spencer Road on Wednesday night.

That stretch of road is a signed 100km/h zone.

Sergeant Day said the motorist was travelling through to South Australia.

"He was driving on unfamiliar roads not known to him in the rain and speeding late at night," he said.

"It is very much a recipe for disaster, I doubt if he had ever driven on the country roads before and he told the Koroit police member that he was speeding to get to South Australia."

The man was fined $454 and his licence was suspended for three months.

In an unrelated incident, a 32-year-old unlicensed driver has had his friend's mother's car impounded.

Sergeant Day said the man was intercepted in Dennington on Friday morning.

He said Koroit police members knew the motorist didn't have a licence because he was caught riding a motorbike with false plates back in May.

The vehicle he was driving was impounded at a cost of $1338 and the motorist was summonsed to appear in Warrnambool Magistrates Court at a later date.

Have you signed up to The Standard's daily newsletter and breaking news emails? You can register below and make sure you are up to date with everything that's happening in the south-west.