87 is about our 91, 91 is about our 95. roughly add 4 to the US octane rating to compare with Oz
Why is it so? I know the US gallon is six (imperial) pints versus the UK gallon of eight pints, so I 'spose that do as they wish.
Let's keep the hijack alive!
I've only ever used 91 in 193,000 kays on ST13s and 42,000 on my ST1100. I haven't noticed any pinging and haven't destroyed any engines. I'm saving 10¢/litre. What's not to like? Oh, and I get around 4.82 l/100km on a trip and have seen the double ton once upon a time.
Fuel consumption on the Mighty ST1300 is generally 5.5 litres / 100km, as high as 6.5 when riding really hard, as high as 7.5 towing the Elite camper, below 5 has been achieved when riding at pussy speeds (80 - 90 km/h) on a freeway.
This is generally on our 91 rated fuel. I don't notice any improvement at times when high rating is used.
BTW, did I mention that on a recent two month tour of the USA and Canada we drove a Hyundai Sonata, what a nice little car it is. I mention it here because it was surprisingly fuel efficient, averaging around 45mpg on 87, and 52mpg on 91. Considering highway and freeway speed limits were often 65, 70, 75 and 80
km/h mph <edit 10:33am 24 May 2017> and travel speeds were 5mph above the limits. I reckon this was pretty good, certainly better that what is achieved in Mrs W's comparable Mazda 6.
One leg of the trip, Dillon to Glenwood Springs in Colorado, we achieved 58mpg over approximately 90 mile. This was with the cruise control set on 75mph. I suppose the 5,000ft drop in altitude may have had something to do with it.
And then there was this:
Grand Canyon Village to Cameron, AZ - approximately 60 mile and a 3,500ft altitude drop.
No "free wheeling" in either situation.