Brian McKandie was found beaten to death with a "heavy weapon" in his home in Rothienorman on 12 March.
Police Scotland has again appealed for anyone with information that could help to get in touch, almost three months after the attack.
Two men were seen speaking to him the day before, and a burgundy or maroon car was also seen at the time.
One of the men is described as possibly 30 to 50 years old and of heavy build. The other was possibly 20 to 30 years old, and of a much thinner build.
The estate-type car may have had a rear passenger side panel of a different shade.
Det Ch Insp Iain Smith said: "We are now almost three months on from when Mr McKandie was murdered and we would like to repeat our appeals to the public for assistance.
"House to house enquiries are almost concluded with over 1,000 people seen who live within a few miles of Mr McKandie's home.
"These two males and the car remain unidentified, as do a number of other persons who may have attended at the address to speak to Mr McKandie.
"It is believed that Mr McKandie may have known his attacker through either friendship, business or through a third party he has been introduced to.
"A large customer base that used Mr McKandie's services as a mechanic has been identified during the inquiry, but we believe others have not come forward to date.
"Whilst they may not necessarily think it is beneficial or relevant to the investigation, please report it and let us make that judgement."
Mr McKandie's brother William earlier said the victim was a "private, gentle man".
Police probing the murder of a 67-year-old man at his Aberdeenshire home believe he may have known his killer.