Just a follow-up 87 burns at a faster rate than 91 octane fuel.  Also, use
what your owners manual or the manufacturer recommends.  I know my autos say
use 87 and my bike says use 87 or higher.  I use higher because it prevents
knocking when the bike gets hot especially in traffic.

Actually the additive packages AND detergents are different between most
brands.
Techron is a detergent package that is advertised as such, but most
companies have a similar package as well. These are needed to keep the
entire fuel system clean and functional. They reduce gum formation and
break down any existing deposits.
The base stock MAY be the same for each brand though. The states
themselves do NOT require different packages, however the companies may
change formulations to help reduce the effects of the seasons on
emissions.

http://www.faqs.org/faqs/autos/gasoline-faq/part1/  For a FAQ that
should answer any questions about gasoline.

4.12 Are brands different?

Yes. The above specifications are intended to ensure minimal quality
standards are maintained, however as well as the fuel hydrocarbons, the
manufacturers add their own special ingredients to provide additional
benefits. A quality gasoline additive package would include:-
* octane-enhancing additives ( improve octane ratings )
* anti-oxidants ( inhibit gum formation, improve stability )
* metal deactivators ( inhibit gum formation, improve stability )
* deposit modifiers ( reduce deposits, spark-plug fouling and
 preignition )
* surfactants ( prevent icing, improve vaporization, inhibit deposits,
 reduce NOx emissions )
* freezing point depressants ( prevent icing )
* corrosion inhibitors ( prevent gasoline corroding storage tanks )
* dyes ( product colour for safety or regulatory purposes ).

During the 1980s significant problems with deposits accumulating on
intake
valve surfaces occurred as new fuel injection systems were introduced.
These intake valve deposits (IVD) were different than the injector
deposits,
in part because the valve can reach 300C. Engine design changes that
prevent
deposits usually consist of ensuring the valve is flushed with liquid
gasoline, and provision of adequate valve rotation. Gasoline factors
that
cause deposits are the presence of alcohols or olefins [46]. Gasoline
manufacturers now routinely use additives that prevent IVD and also
maintain
the cleanliness of injectors. These usually include a surfactant and
light
oil to maintain the wetting of important surfaces. Intake valve deposits
have
also been shown to have significant adverse effects on emissions [47],
and
deposit control additives will be required to both reduce emissions and
provide clean engine operation [48]. A slightly more detailed
description
of additives is provided in Section 9.1.

Texaco demonstrated that a well-formulated package could improve fuel
economy, reduce NOx emissions, and restore engine performance because,
as
well as the traditional liquid-phase deposit removal, some additives can
work in the vapor phase to remove existing engine deposits without
adversely
affecting performance ( as happens when water is poured into a running
engine
to remove carbon deposits :-) )[49]. Chevron have also published data on
the
effectiveness of their additives [50], and successfully litigated to get
Texaco to modify some of their claims [51]. Most suppliers of quality
gasolines will formulate similar additives into their products, and
cheaper
product lines are less likely to have such additives added. As different
brands of gasoline use different additives and oxygenates, it is
probable
that important fuel parameters, such as octane distribution, are
slightly
different, even though the pump octane ratings are the same.

So, if you know your car is well-tuned, and in good condition, but the
drivability is pathetic on the correct octane, try another brand.
Remember
that the composition will change with the season, so if you lose
drivability, try yet another brand. As various Clean Air Act changes are
introduced over the next few years, gasoline will continue to change.

What kind of timing, compression, cams, or boost are you running, and on
what engine? Bone stock Dodge Ram, you will be disapointed...