The car was found in Ajana, more than 500km north of Perth and east of Kalbarri, on Friday.
He has not made contact with any friends or family.
Authorities continue to search rough terrain for Mr Allison on Sunday.
Police and SES volunteers on foot and in four-wheel drives are focusing their efforts around the area where his car was found.
A fixed wing aircraft is flying over and police divers will search nearby waterways in the afternoon.
Police say Mr Allison was fond of the Kalbarri area and are asking people in the area to keep an eye out.