What Octane Petrol for 4L V8

In victoria there appears to be a few different varients of E10, most the leading chains list it as a low octane fuel, me thinks to keep people buying higher octane fuel. United fuel E10 is rated at 95 RON and is sold at a discount to even their normal unleaded. Reasoning is that the fed gov offers rebates for E10 fuel and United only being a bit player is working for market share. OK so the fun part is pricing;
United E10 140.9
United ULP 143.5
Caltex/Shell/BP 95 ron 153.9

so i run my D2A V8 on the E10. Every now and then i run half a tank of 98 RON through it but as for economy the E10 returns around 15L/100 same as the 95 RON, 98 marginally better. Just to add to it all United also have 100 RON available at some outlets. If we are talking dollars im sticking with the United stuff. By the way im up in Rochester near Echuca and we are screwed on price, it never, i mean never changes. Also have covered over 30,000kms in last 9 months

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Originally Posted by Andrew D

I'll give this a go and see what happens. I need a 7% improvement on fuel economy just to break even if the fuel price is $0.10 per litre different (560km/90 litres:o). I think I will be doing well to achieve this but time will tell.

Regards
Andrew

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Funnily enough, when petrol prices rise, it actually makes higher octane fuels more economical compared to the low octane fuels. for 7%, $1.40 is about the cut off if the gap is 10c.

I am one of those people who document fuel use v distance travelled (yes! one of the people with no life:D), and have done for the past year using both 91 and 95 rated octane fuel at different times.
The main column that I track is cost per kilometre.
I can tell you that there seems to be little difference in cost per kilometre no matter what fuel is used.
As the vehicle runs noticeably better using the higher octane fuel, I can see no reason for running the cheaper stuff.
Note that my vehicle use is pretty consistent, mainly to get me to work and back (40km round trip) five days a week.