Snick, The 84 mpg target isn't my personal main priority. I actually think it's a very optimistic goal and the Elio will be hard pushed to achieve it. I certainly wouldn't expect to achieve it in practice. I'd rather have decent handling and decent tyre life with replacements at reasonable cost than squeeze the ultimate mpg.
What size tyres would you expect to be fitted as standard and where will they be sourced? Any narrower than 5 inch tread and you are looking at round profile motorcycle tyres, which I wouldn't want, they were originally recommended and supplied by the designer of my trials car but they made the car unstable and they wore out very rapidly because a car only uses the middle of the tread.
Certainly the Elio prototypes seen so far don't have exceptionally narrow tyres and they certainly aren't motorcycle tyres.
We have a Fiat Panda 1.3 diesel in the family which is quite capable of giving well over 70 mpg (imperial gallons) and it uses 155/80/13 tyres. These are very readily available in UK, probably the cheapest size available, costing about one fifth of the 5.25 x 16s I already mentioned. I wouldn't want to have to buy a hugely expensive, special set of tyres like those every time on a commuter car, because it's all part of the running expenses equation. If the Elio needs highly expensive special tyres to achieve the mpg target, it would be a big mistake as far as I'm concerned.