Very poor gas mileage

[Malachias]

Bonnie 1992 SSEi with 55.000 miles on it Supercharged
New coils, new wires and sparks and new O2 sensor. No codes when scanned
with TECH II Scanner. Usualy I got 18/gal in drive city and about 21/gal at highway with a brasilian gaz that has 25% ethanol. One month ago drop a half
the gaz mileage 9/gal city and 12/gal highway. No gaz leak , no gaz smell with same stand drive. Just one driver. Tires in good conditions (31 lb/pol)
No potholes falls, car in great shape, no brakes grasping the wheels.
Fuel pump and filter changed (one year old) and correct pressure at the trail
(41 Lb/Pol ). Any sugestion or tip for to start search will be welcome.
Malachias (Brazil)

[Malachias]

Anybody can help me?

[maxwedge]

Many things can cause a mileage drop where you are could be an increased amt of ethanol in the fuel, you are not aware of. Also look inside the fuel pressure regulator hose for signs of gas. When using the Tech 11 you should have seen fuel trims trying to remove fuel if the engine was running rich enough to cause this, did you?

[Malachias]

Thanks a lot Maxwedge for your help.
I bought this car brand new there in USA (Tallahassee/Flórida state capital) and drove it there for 3 year using a premiun fuel. Whem I cameback to Brazil I brought it with me in 1997. Since it I had been driving it with the brazilian fuel (25% ethanol) with no major issues. As you advise me I took a look at the fuel pressure hose(look like brand new) and no leaks or gaz smell.
For this 11 year driving here in Brasil, even with 25% ethanol I got a decent mileage 17MPG in a mix drive (city/highway) and about 2 months ago this mileage dropped sudden for a half. As I said I have new sparks (dual pratinnum) news wires, cheked the coils (OK) and new O2 sensor.
Because the high ethanol mix I usualy change my fuel pump every 2 year.
The TECH II scanner dind´nt show nothing wrong: all the parameter it´s OK.
The car dind´h change their behavior and runs flawlessly, only 52.000 miles on it and just one onwer and driver. But the mileage now is hurting my pocket.
What do you think about a clogged catalizer (ethanol corrosion) ? Do you know how to check it?
My best regards.
Malachias

[Malachias]

Hello MAXWEDGE (Moderator)
I´m still waiting for your advice.
A happy new year to you and all at this forum.

Malachias (Brazil)