Speedometer reads 30mph to fast
Depends on what system you have, it could be a speed sensor, wrong speedo gear on the end of the drive, speedometer drive motor, worn out speedometer head. This is a general cause I do not know what type of speedometer you have.
Search Buick Skylark Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Buick Skylark Experts