I do a mix of commuting from Vancouver to Richmond during the week (15km each way in heavy traffic) and weekends in Squamish or Whistler (ie. mountain highway).I was seeing around 15litres/100km worse case, 13.3 average, and 10 best case (on 90 octane).
The best consumption figures I have got so far have been with 90 octane from the Husky in Whistler (circa 21.5mpg combined) which equates to around 600km per tank according to the computer. That was about 28mpg on the return trip to Whistler, but dropped when I went back to my commute so in city traffic it's definately in the teens. The worst has been with 89 from the Cheepocrappysavagasplace in Richmond. That went down to around 16mpg combined and in the city was around 12 ... pretty awful! I may as well have been using cat pee.
I tried 89 & 91 from other regular (Esso) gas stations and noticed no difference (18mpg combined) other than in what I was paying. I tried 94 for one tank and that seemed to make no noticeable difference either with economy although perhaps a bit more gutsy with acceleration ... still around 18mpg though. I haven't found anywhere that stocks 96 (as recommended in the manual).
So I'll be sticking with 90 when I can get it as gas in Whistler & Squamish is also cheaper than in Vancouver (by about $0.07 per litre). I'll probably alternate between 89 & 90 with the occasional 94 the rest of the time if I fancy giving the engine a treat ;-)
OK it's not really free but it helps to think of it this way when paying close to $1.50/litre;-)
With the G35 I just wasn't sold on the looks, although again it was a hoot to drive. What finally swayed me was that I was told you can't get roof bars for the G35 ... bit useles for a keen skier.
