E 85 fuel question

[PICKUP6772]

Hey guys. My Town Car has 435,XXX on it, and I know the previous owner ( Limo company/regular service at our shop) only ran straight gasoline in it. With this kind of mileage, can I run E-85? With the rising cost of fuel, along with the price difference per gallon ($1.559/$2.799), would it be safe to switch over? Obviously, with that big a price gap, the drop in economy would be negligible.
MIKE

[Mainemantom]

You can run the E-85 however you will notice that it does not run well. First of all the E-85 gas does not last. Only about 30 days. gas without ethanol lasts much longer. It does not gum up your fuel system either. If you store your vehicle, I discourage using anything other than ethanol free. Gas mileage and performance are better. In our area, Citgo supplies the ethanol free 90 octance at $2.99 a gallon. Can't speak of other areas of the country. Pay the extra price for good gas now or pay for expensive fuel system repairs later.

[Tiggie]

As long as your car is flex fuel, you can.

I wouldn’t unless you are driving it daily and go through a lot of fuel per month.

We don’t really have E85 locally. A few stations have started with an E15 option. I run the E10 stuff in my daily drivers but my other stuff gets the non ethanol fuel.

[PICKUP6772]

Here in New York, all stations are minimum of E10. I do notice a big difference, when I gas up car with the ethanol free in West Virginia when I go to visit my mom. The car is my daily driver, running about 35 miles round trip to work. And then I do a run around with it a lot on the weekend.
Mike

[gadget73]

The fuel mixture will be way off for E85. I also don't know about the O rings and other parts in the fuel system. If you replaced the rubber parts and tuned the ECM to deliver the additional fuel needed, no reason it wouldn't work. Won't gain you anything, fuel might be cheaper but its going to use more of it, plus the cost of conversion. Would likely take a long time to pay for itself.

Where it might make sense is if you were running it boosted. The higher octane of the ethanol is much less prone to detonation, which is helpful for elevated cylinder temps.

otherwise, stick to E10.

[GM_Guy]

What year is the tc? A flex fuel panther will have the colder spark plugs, bigger injectors, and a flex fuel computer that determines what your ethanol/gas mixture is based on a few factors occuring upon startup.

[PICKUP6772]

GM Guy,
As I said, it's a 2010, and it is Flex Fuel. It's the high mileage, and the fact the previous owner NEVER used E-85, that has me questioning whether or not to use it.
Mike

[gadget73]

oftenimes the smart money is on not messing with things

[sly]

2010 won't care. The lines are all designed to take ethanol. The only issue you would have is if the fuel content sensor is wonky. But that would probably cause issues with regular gas too.

[GM_Guy]

GM Guy,
As I said, it's a 2010, and it is Flex Fuel. It's the high mileage, and the fact the previous owner NEVER used E-85, that has me questioning whether or not to use it.

I don't read every thread here if you mentioned it elsewhere.

2010 won't care. The lines are all designed to take ethanol. The only issue you would have is if the fuel content sensor is wonky. But that would probably cause issues with regular gas too.

Don't even need to worry about that, there isn't one, the computer determines ethanol percentage. Does its magic when certain conditions are met (fuel fill being a primary factor), monitors sensors and bases its fuel tables on the results.

Alex.

[GM_Guy]

In order to maintain proper fuel control, the PCM strategy needs to know the stoichiometric Air/Fuel Ratio for use in
the fuel pulse width equation. On pre-2000 MY flex fuel vehicles, the percent alcohol in the fuel was determined by
reading the output of the Flex fuel Sensor. The percent alcohol was stored in a register called Percent Methanol
(PM). Although current alcohol-blended fuels only include ethanol, the percent methanol nomenclature has
persisted. On 2000 MY and later vehicles, the Flex Fuel Sensor has been deleted and PM is inferred. The strategy
to infer the correct A/F Ratio (AFR) relies on the oxygen sensor input to maintain stoichiometry after vehicle
refueling occurs.
[...]
The fuel level input is used to determine if a refueling event has occurred, either after the initial start or while the
engine is running. If refueling event is detected (typically calibrated as a 10% increase in fuel level), the PCM tracks
the "old" fuel being consumed by the engine. After a calibrated amount of "old" fuel has been consumed from the
fuel lines, fuel rail, etc., the "new" fuel is assumed to have reached the engine. Normal long term fuel trim learning
and purge control are temporarily disabled along with the evaporative system monitor and fuel system monitor to
allow the composition of the fuel to be determined. The filtered value of short-term fuel trim is used during closed
loop to adjust AFR in order to maintain stoichiometry. During learning, all changes in AFR are stored into the
AFRMOD register. As updates are made to the AFRMOD register, the fuel composition register (PM) is updated
and stored in Keep Alive Memory. Learning continues until the inference stabilizes with stabilized engine operating
conditions. The PM inference and engine operating conditions are considered to have stabilized when all of the
following conditions are satisfied:

• ECT indicates the engine has warmed up (typically 170 °F) or an ECT related fault is present.
• Enough "new" fuel has been consumed (typically 0.5 lb - vehicle dependant) to insure fuel is adequately
mixed.
• The filtered value of short term fuel trim is in tight fuel control around stoichiometry, (typically +/- 2%) for at
least 5 O2 sensor switches or AFRMOD is at a clip.
• The engine has been operated for a calibratable length of time, based on ECT temperature at start
(typically 200 sec. at 40 °F and 30 sec at 200 °F) or an ECT related fault is present.
• The engine has been operating in closed loop fuel, with the brake off, within a calibratable (off-idle) air
mass region (typically 2.4 to 8 lb/min) for 5 seconds, to minimize the effect of errors such as vacuum
leaks.

Once the value of PM has stabilized (usually about 7 miles of driving), AFRMOD and PM are locked and deemed
to be "mature." After PM is deemed "mature," normal fuel trim learning and purge control are re-enabled along with
the fuel system monitor and evaporative system monitor. Any observed fueling errors from that point on are rolled
into normal long term fuel trim (via adaptive fuel learning).

All remaining OBD-II monitors remain enabled unless AFR is observed to be changing. If AFR is changing, all
monitors (except CCM and EGR) are disabled until the AFR stabilizes. This logic is same as was used for FFV
applications that used a sensor. The AFR rate of change required to disable OBD-II monitor operation is typically
0.1 A/F (rate is based on the difference between a filtered value and the current value). For a fuel change from
gasoline to E85 or vice versa, AFR typically stabilizes after 2 to 3 minutes on an FTP cycle.

If a large refueling event is detected (typically calibrated as a 40% to 50% increase in fuel level), the PCM strategy
tries to assign the "new" fuel as gasoline or ethanol (E85) on the assumption that the only fuels available are either
gasoline or E85. The strategy performs this fuel assignment to gasoline or ethanol (E85) only if the "old" and the
"new" stabilized inferred fuel composition values are within a specified amount of each other (typically 5-10%),
indicating that the fuel in the tank is the same as the fuel that was added and therefore must be either gasoline or
ethanol (E85). If the "old" and "new" stabilized inferred fuel composition values are not near each other, the fuel
added must be different from what was in the tank and the strategy retains the current inferred value of PM until the
next refuel. By assigning the fuel to gasoline or ethanol (E85) in this manner, normal fuel system errors can be
learned into normal long term fuel trip for proper fuel system error diagnosis.

After a battery disconnect or loss of Keep Alive Memory, the strategy will infer AFR immediately after going into
closed loop fuel operation. A vehicle that previously had fuel system errors learned into long term fuel trim will infer
incorrect values of AFR. After the value of AFR is determined, it is fixed until the next refueling event. If the next
refueling event is performed with the same fuel (either E85 or gasoline), the value of AFR will not change. The fuel
is then assigned to be E85 or gasoline as explained above. The long term fuel trim will again be a reliable
indication of normal fuel system errors.

Only one large tank fill is required to assign the fuel as being either gasoline or ethanol, if the inferred AFR did not
change significantly. If AFR did change significantly, several tank fills with the same fuel may be necessary to
assign the fuel as gasoline or ethanol.

As the vast majority of vehicles are expected to be operated with gasoline, the initial value of AFR is set to
gasoline. This is the starting point for the AFR after a battery disconnect and will allow for normal starting. Some
vehicles may have E85 in the fuel tank after having a battery disconnect, and may not have a good start or drive
away. The startability of alcohol-blended fuels at extreme cold temperatures (< 0 °F) is difficult under normal
conditions; these vehicles may be required to be towed to a garage for starting if a battery disconnect occurs.

..

[sly]

Interesting. Good to know.

[PICKUP6772]

Alex, I've been busy as hell, and just realized I didn't mention the year in the original post. My apologies.
Mike