I haven't read through the whole manual yet but it doesn't say anything on the fuel gage or fuel cap about premium fuel only. But I use premium anyway, got used to having to due it with my 04' GTO.
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2007 GXP Stealth Grey Metallic
Best Beltronics Accelerometer Times so Far: 0-60: 5.40 1/4: 14.22 @ 98.6