Tinsley's body was discovered about 300 feet down an embankment along Highway 18.
Tinsley was last seen on New Year's Eve outside his Arcadia home on the 600 block of West Fairview Avenue. When family members lost contact with him, they reported him missing to the Arcadia Police Department and gave detectives his vehicle description.
It was four days later at about 1 a.m. Monday when a Calif. Highway Patrol officer spotted Tinsley's silver 2007 Toyota Matrix in the San Bernardino Mountains, stopped along Highway 18, a stretch of road known as the "Arctic Circle."
The San Bernardino County Coroner's office will determine the cause of death.
"We initiated a search-and-rescue to check around the vehicle for that missing person," said San Bernardino County Sheriff's Spokesperson Jodi Miller. "At approximately 6:15 this morning our search-and-rescue members found a male victim."
Authorities don't suspect foul play and Tinsley didn't have any serious health problems. Police said it appears Mr. Tinsley drove to the location under his own power.
His family said the 81-year-old man loved to come up to the mountains.
"Unknown as to how it happened but apparently his family did mention that he did love to be outdoors and he very well could have gone up just admiring the view and it's unknown how the unfortunate accident occurred," said Miller.
Anyone with information about the case was urged to call the Arcadia Police Department at (626) 574-5151.