Our Audi's get way extra MPG on premium. Up to 20% on my turbocharged.
Also (probably not an issue for you, but) they increase engine life by up to 50%.

If people bothered to read their literature they would find most manufacturers recommend filling with premium one in three times even on low end models to get the benefits of the added cleansing agents.
The plate on the inside of the fuel cap cover tells you the minimum RON, not the maximum.