Driving, using (even as a passenger), or interfering with a motor vehicle knowing that such use is without the owner's consent is an offence [Criminal Law Consolidation Act 1935 s 86A].
Maximum penalty:
For a first offence: imprisonment for 2 years
For a second offence: imprisonment for 4 years (a minimum of three months)
Additional penalty:
A person convicted of illegal use of a motor vehicle will also be disqualified from driving for at least twelve months. This applies to both first and subsequent offences [s 86A(2)]. The person may also be ordered to pay compensation to the owner of the motor vehicle [s 86A(5)].