Have to say, I find fueling limitations significantly less attributable to emission based qualities than to mechanical deficiencies.
Already, sulfur caps are fairly low. And it's like alot of the other mandates, real values are generally maintained low, in order to keep a nice cushion from mandated caps. For example, sulfur in ULSD stays considerably lower than the standard 15 ppm cap. I believe LSD has now been fully phased out and transitioned to ULSD, 15 ppm or less.
Gasoline is similar. I've never seen more than 30 ppm in the RFG around here. Though, our PQI standards don't require regular sulfur analysis in any but diesel fuel.
Also, if you want to maintain high lubricity in gas, always buy premium branded. Shell, for example, has the highest treat rate of their additive in their VPower. Additive, in addition to detergent priperties, lubricates and offers anti-gumming agents and other qualities as well. Seeing as ethanol in fuel is pure alcohol, with a denaturant and no additive, I'm not sure how it offers much lubricity.