Darren thanks for that, but Toby's test there is with three 3.0 v6 which are not even slightly similar to the SS 6.0 that the OP was asking about.
OP it's definitely worth it
when your car is tuned closer to stoich and timing advanced - can get 6-11% more HP and TQ than 98 without KR (engine knock retardation) pulling you under the curve. Keeps everything running better for longer, my car has drunk more than 12,000 litres (2/3 of a tanker) over the past couple of years since new, average 13l/100k with a boot full of booze, helps save the ozones and shoots wicked white flames out back too!
As to cost / benefit, basically with the added cajones... any time price is less than $1.35/litre. However at the moment, being 60-65% ethanol in most servos running out the winter blend, you won't get the performance or reasonable economy unless you remap the crappy stock tables. So why not get you car breathing better and have it dyno tuned for alcohol fitness to get more out of it for less. Then logically it goes like this:
IF ([price_98] - 20%) > [price_e85] AND [price_e85] < $1.35 THEN e85 ELSE 98.
