Aberdeen has a few sites. The X40 used to run between Bridge of Don and Kingswells as a dedicated services with specific P&R fares but these have long been done away with as has the X40 service. All sites are free parking and pay on the bus.
Bridge of Don - served by First, service 1b on Monday to Saturday, no Sunday service. The site is also in easy walking distance of several other services.
Kingswells - served by Stagecoach, primary service is X17 but others do call. No longer served by First. Site is well used by locals, more as a bus terminus but still reasonably used as a P&R.
Craibstone - served by Stagecoach. New(ish) site which was served by First for a short time. Despite its presence on the busy A96, it sees little patronage, not uncommon to see just two to three cars parked in the hundreds of spaces.
Not strictly in Aberdeen itself but the Ellon park and ride, is arguably the most successful. Served by Stagecoach with a variety of services and destinations.
There is also the Charleston of Elsick site to the south. I’ve not been there so not clear on how well it’s used.
There are also two former sites at Westburn Road and Wellington Circle which were seasonal sites but these have both been closed for some time.