The self-regulating code of practice is designed to promote and safeguard consumers' interests by helping them identify better businesses, while encouraging garages to raise their standards of customer service.
Shoddy servicing is estimated to cost drivers £4 billion a year.
'Our customers now have the added confidence of this further commitment to continued good service,' said Andrew Hutton, group service manager for Arnold Clark.
To date more than 5000 garages have signed up to the code. It offers motorists:
You can find out more at www.motorindustrycodes.co.uk