Staffordshire Police announced on Friday that the 17-year-old boy had been arrested in connection with the collision on the A5 on January 1 which killed a pensioner.
Joan Hill, aged 73, from Rugeley, died following the collision near the Longford island in Cannock after the red Peugeot she was travelling in was hit by a blue Ford Kuga.
The teenager, from Walsall, was detained on suspicion of causing death by dangerous driving, failing to stop at the scene of a collision, aggravated vehicle taking, attempted theft from a motor vehicle, theft of a motor vehicle, burglary with intent to steal, theft from a person and arson.
Staffordshire Police have confirmed he has since been placed on conditional bail while inquiries continue.
A spokeswoman said: "The fourth juvenile arrested in connection with the fatal collision on the A5 recently has since been placed on conditional police bail while inquiries continue.
"Anyone with information relating to the collision should submit it via our portal at mipp.police.uk/operation/STAFFS23K02-PO1."
The 17-year-old became the fourth teenage boy to be arrested, with three other youths - two aged 15 and one aged 17, all from the Walsall area - all arrested on Wednesday on suspicion of the same offences.
They have also been placed on bail pending further inquiries.