The reason
guzzla has never noticed any difference between brands is because there
isn't any difference between brands. (Well, none that you can pick this side of professional-grade test gear, and probably none worth mentioning then either.)
But there is, of course, a difference betweenb different
types of petrol. Premium fuel Shell Ultra (just as one example, there are equivilents in all the other brands) will take you measurably further on a tank, and makes most modern cars a litle more nippy. The performance difference is very small and hard to measure, but the economy difference is quite significant and very easy to measure. 98RON like Ultra consistently takes you further on each tankful.
Of course, it costs more too, so you have to trade off the cost against the benefit. You can't give a hard and fast rule like "95 RON is the overall best for economy" because the price difference changes all the time. One day the 98 octane will be the best buy (costs a bit more but takes you further), the next weekprices change and you are best to get the cheapest E10 ethanol blend 'cause it's quite a lot cheaper than standard 91 and you get more miles per dollar.
So:
- if you mostly care about performance, buy expensive 98 RON.
- if you mostly care about getting long range from a tank, always buy 98 RON.
- if you mostly care about economy, buy whichever one is giving the best bang per buck at the time - this could be any type at all - E10, 91, 95, or 98, all depending on the prices.
- if you mostly care about doing your little bit to minimise global warming damage, buy E10 because then only 90% of your fuel is fossil-based and the other 10% is renewable and does no harm cause it grows again next year and re-absorbs all the carbon in it. (Technically, it's a bit less than 10% because there is usually some small amount of fossil fuel used in the manufacture and transport of the ethanol. Call it 8% or 9% at a guess. Still a lot better than 0% any way you slice it.)
In a perfect world, you would have careful measurements and a smartphone app to tell you that E10 at $1.29 is cheaper per mile than 95RON at $1.36 but 98 RON at $1.39 is betterthnan either (just example numbers, don't quote me on those). But in the real orld, you just look at the prices and make your best educated guess.
Rules of thumb:
- 5c extra per litre for a step upgrade (91 to 95 or 95 to 98) is worth paying.
- 10c extra per litre for a step upgrade is not worth paying.
- but these rules ^ should really be expressed in percentage terms, so when petrol is very dear ($1.94 a litre in an outback town, for example) the 10c is worth paying. Besides, out there you probably need the extra range. And if petrol is very cheap, adjust the other way.
Territory
- E10 is usually either equal best value or outright best value, but watch those price differences! Sometimes E10 is only 1c or so less than 91 RON, which makes it cost more per kilometre overall. So you can't just buy E10 every time and be sure you are getting best value.
- 95 RON tends to be the most expensive per kilometre - you are only getting a one-step economy upgrade but the price difference can be large. Of course, sometimes it is the best value. Stay alert!
- 98 RON can be very dear but it's often not much more than 95 RON and worth the 2c or 3c difference. As always, check each time.
Me, I like to use E10 wherever I can for envionmental reasons, but I'm damned if I'll pay overs for it, and you can't get it everywhere, so I wind up using E10 a lot, but also 98 or 91, and sometimes even 95 if the price is right.
