All of these vehicles must use lead-free gasoline. It is recommended that these vehicles avoid the use of premium grade gasoline. This is due to the engine control system being calibrated towards the use of regular grade gasoline. The use of premium grades may actually cause driveability problems. Also, Mazda advises against the use of gasoline with an octane rating lower than 87 which can cause persistant and heavy knocking, and may cause internal engine damage.