My previous car was a Pajero V6 petrol. I did a test over about 9 months comparing E10, 95 and 98. I found that the extra cost of the higher octane fuels was more than offset by better fuel economy plus better performance as a bonus. I would not personally go below the recommended octane rating though. FWIW, our mechanic (very well respected around this area) said never to use E10 due to water issues. He had seen a number of petrol tank rusted and the only common factor was E10 fuel. Bottom line is you may save more by going for a higher rating. I ended up using 98 octane afterwards. My experience may not be the same as yours, and I know it's not the same car, but it's worth keeping a record to see whether you get the same result and act accordingly.
Martin

