I have previously had 2.6bar(38PSI) in the rear and 2.4bar(35PSI) in the front. Treadwear seemed very even but MPG was much lower. Grip was excellent though.
Last month I changed closer to the recommended at 3bar(43.5PSI) rear and 2.5bar(36PSI) in the front. MPG went from 27 as a weekly average to 30. Grip is still good, probably marginally lower but hard to tell. I'll keep an eye on treadwear.
Road noise is a little lower and ride seems to be better which seems counter intuitive. Front axle seems happier with the higher pressure so will probably stay at these pressures unless I notice uneven wear.