As an ExxonMobil employee, I am not in a position to misinform on
this subject, so I will do the best I can. The Exxon/Cors (legal
name) has once again jumped the gun and will be replacing regular
unleaded with Gas/Ethanol 90/10 (Gasohol, 90% Gas, 10% Ethanol) at
all corporate owned stores. These stores inclued but may not be
limited to, On The Run, Tigermart, Tigermarket, Exxon, and Mobil
branded stores. From the research I have personally done, All
current vehicles can run on  a blend of gas/ethanol up to 85% gas
10% ethanol. Gasohol as it is called produces less carbon monoxide
emissions, but can however raise other harmful emissions levels in
warm weather as well as cause seals to prematurely wear out, damages
certain finishes, clean out your fuel system (more in a moment), and
separate water more so than regular Gas. As for the cleaning part,
the Gasohol blend at first impemination only causes sediment and
debris in your fuel system to be lifted into the fuel. Of course
this will be caught by your fuel filter, but your fuel filter will
clog VERY fast. Our corporate offices are arranging to have all
ExxonMobil underground storage tanks cleaned thouroghly, and filters
changed in preperation for the new Gasohol. They are warning us that
even though the tanks will be cleaned there is still the chance of
debris and or water getting into customers tanks which will cause a
stall conditon within minutes of fueling. At this time, I have no
information on how or if ExxonMobil will take car of customers
effected by a stall condition. As described to us, these problems
will only occur during implimentation, as the Gasohol will quickly
remove any debris/sediment from the tanks and dry up any water
missed my the crews cleaning the tanks. I know water in the tanks
sounds scary but here is the simple fact. 99 percent of ALL
underground storage tanks for fuel contain at least 50 gallons of
water. It is inevitable, condensation and rain water causes this
conditon. However there are monitors in place to insure that no
water enters your fuel system, as alarms inside the store are
activated when water levels reach levels high enough that they may
be pulled into the pumps.As gas floats on the fuel is skimmed off
the top of the tank, avoiding water and sediment. Again however, the
new Gasohol will disturb this balance.

I am willing to answer any questions I can, however I AM NOT AN
EXPERT, it is in your best interest to do your own research from
trusted sources.

My whole reason for this post is that I feel the public should know
before the last minute, when the changes are already taking place,
and I am trying to figure out where my fuel filter is on my 91
sentra so that if I encounter a clogged fuel filter, I can just
replace it quickly and be on my way. If anyone knows offhand where
it is please reply.