Almost any vehicle with adjustable ignition timing can run regular gas, by retarding the ignition timing, or in the case of a turbocharged engine, lowering the boost. Of course both of these options usually result in a loss of power. Spark lead directly affects detonation, which is the key factor that would tell you if the fuel octane is inadequate. If you have a loud exhaust, this might be difficult to determine. Audible detonation (knocking or pinging) should be avoided, since it can be very destructive to internal engine parts.
The bottom line, if you want to run lower octane fuel, lower the boost or retard ignition timing, if you hear knocking or pinging.:yup: