Hi, My girlfriend has had a C2 (1.4) for about a year here in the UK (from new). We've always filled up with standard unleaded fuel. We didn't think to try a higher grade fuel partly because it's not a performance car, and partly because a few years ago, I tried my old Porsche 944 on the good stuff, and found that I gained performance but didn't save any money (with 70 and 30 mph speed limits, there seemed little point).
Anyway, we thought we'd try a tank of 98RON fuel instead of the normal
95RON in the C2. It was 2p/litre more (90.9p instead of 88.9p). We are a little stunned by the difference. We do a lot of short trips and stop- start motoring, with the occassional long haul. Our average fuel consumption overall on 95RON was 37.6mpg, with long-hauls returning something like 41-42mpg. We haven't done a long-haul yet on the 98RON fuel (just short runs and stop-start), but the average is coming out at 42.8mpg!If my sums are correct, we're saving over 1p per mile. Once we've done a long trip, I'd expect the figures to get even better.
My new phrase this year seems to be "here's the rub" - don't know why, I hate it... But here's the rub: What octane rating does fuel in France go up to? When we checked the manual to make sure that 98RON wasn't going to blow the engine up, we noticed that the maximum grade is actually higher than 98RON. So, fuel is not only cheaper in France, but there's the possibility that it's better quality than the stuff available in the UK.
Here's another rub: We're a two-car household. Our 1.4 Citroen C2 runs on high octane fuel. Our 2.7 Porsche 944 runs on low octane.