cause driveability problems, reduced economy, higher
Whether this is true or not depends on the brand and local distributor. In the Tribune article you quoted Exxon claims:
"All our fuels are already blended to meet or exceed Top Tier standards," said ExxonMobil spokesman Russ Roberts, adding that he wouldn't comment on whether the oil company plans to join the program."
Even the Babcox article did not claim that all premium included increased cleaning agents compared to all regular gasoline. It was more a warning about low quality gas than a claim about the superiority of premium versus regular.
I have noticed that Shell is now selling premium that supposedly includes increased cleaning additives. But on the other hand, they also claim that their regular has adequate cleaning agents. As a result I am avoiding Shell stations until they stop trying to mislead people into spending an extra $0.20 a gallon. I also stay away from unbranded gas since I suspect they are less religious about meeting EPA requirements regarding the addition of cleaning aganets. I prefer Chevron, Philips, and BP gasoline. I am now staying away from Shell and Texaco (most Texaco stations are actually Shell stations anyhow - at least until the rebranding is completed).
Regards,
Ed White