Hi,
Your experiment kinda shows what others have experienced, that the $/mi figure often remains rather constant.
It WOULD be interesting if someone could repeat it with an 87 octane engine, jumping clear up to the 98. Here in the States we usually only go as high as your "normal" 92. Don't know if they do any better for octane across the border on the Canadian side, or if they just stop at "bigger" gallons!
Rick
This is no mystery at all, it is a result of added lubricants in the gas!
Premium fuel formulations are just that- premium, for added luxury and performance. It is not an issue of octane value only. Premium fuel contains added amounts of detergents to help prevent engine/injector deposits from forming, and for a more luxurious experience contains more lubricants that help smooth and quite the engine. Because of added lubricants there is a very slight, imperceptible almost, improvement in fuel efficiency.
I drive an 2000 Impreza and almost always buy Chevron Premium fuel. The car just runs smoother, which I like. This is the softest fuel around and smooths the engine beautifully- thanks to lubricants, of course. Chevron stated somewhere (I forget where, their official site or somewhere else), that their Premium grade contains more additives than other Chevron grades. Other brands probably do the same to their Premium formulations.
M.J.
This may assist.
I think there might be a different measurement system in North America than in NZ for octanes. I know that our octane rating system is based on two previously separate octane ratings, and then an average is taken between the two.
Yousuf Khan
detergents and other cleaning agents that US gas uses. Namely there's a lot of it in US premium gas, and not a lot of it in US regular gas. But in Canada, there should be an equal amount of it in both regular and premium gas.
Yousuf Khan
Interesting. In Australia we use RON, determined in a standard test engine, whereas in the USA, you use an AKI, Anti-Knock-Index.
98RON is about 93 AKI, 92 RON is about 87. Source:Thanks for the pointer.
Yeah exactly, our index is a halfway point between the RON number and the MON number. We don't normally see more than 91 AKI gas around here, which would correspond to 96 RON for you guys.
Yousuf Khan
That's available too. Some places even have all three.
Just to follow up on this thread. I've just tried my second tankful of other-than-regular, this time I filled with 89 octane mid-grade; it took a while to empty the last tank as I haven't been on the highway in a couple of weeks, which is what I use my car mostly for these days. There's something definitely going on here that's helping. I managed to get 9.4 l/100km (30 mpg Canadian) with this tankful. This included some significant amount of city driving too, not all just highway like before. The engine feels a lot smoother too. I've occasionally had hesitations in the past when starting off from a stoplight, a somewhat occasional jerk or bucking. Haven't noticed it at all since doing the switch.
Now in my original message (quoted below) I said that I got 31 mpg on the half tank of 91 octane high-grade I took last time. But I don't think that means that the higher octane I take, the better the mileage I get. It probably just reflects the fact that I measured the last time after doing nearly 100% highway driving. This session I'd say there was a about 15-20% city driving involved, so therefore I got 30 mpg instead. On regular, I used to get 28 mpg on average, driving at the same speed and on the same road.
Yousuf Khan
Yousuf Khan wrote:
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