I just finished the first tankful/week of driving to work after the 86 sat in my yard for 2 years awaiting head gaskets. I'm not complaining at all since I'd been driving my truck at about 15 mpg, but does the 25 mpg in mixed driving sound about right? It's completely stock except the po cut the air pump hose and we left it that way when we reassembled it.
The main reason I'm asking is because that's about the same mileage I used to get in the 93 with essentially the same engine in a much heavier car. Is the multipoint injection that much more efficient than the cfi that it'll 'compensate' for 1000 lbs?
Around 27 highway is typical for a 3.8 in one of these. To get 25 in mixed driving you've done well especially with a CFI. The 5.0 tends to do better than the V6 on the highway but worse in the city, at least in my experience.
Your '86 is maybe 500 pounds lighter than the '93, not 1000 pounds. I found my '91 V6 got decent economy compared to the '85 I replaced it with ('course my '85 was carbureted). The cleaner aerodynamics of the MN12 likely helps offset some of its extra bulk
ditto, My 88 bird w/3.8 aod, 3.08 gears got 27 mpg highway.
a quikie search of the forum wouldve helped answer your question, since there are a bunch of threads on this subject.
but, you left out some important details reguarding this issue...
what trans/rear combo do you have?
all city or highway, some city&highway driving?
just you in the car or loaded up?
here is one link to help you answer your question
http://foxtbirdcougarforums.com/showthread.php?t=20030
:edit: just noticed how old the post is :P egg on face
A quickie reading of my original post would've answered most of your questions...
All stock 86 V6s had AODs, CFI and 3.08 gears.
I said 'mixed driving'.
Though I'd like to be that 'green' I don't carpool and haven't historically. I'm like about 90% of the rest of the folks going to work every day in the US - alone.
Not a lot of comparison info in that thread on MN12s or recently repaired head gasket cars....
Just FYI, the AOD was an option on 3.8 V6 Cougars and T-Birds in 1986. The standard transmission was still the C5.
The C5 gets worse highway, and about the same city. I got pretty good mileage out of my old 87 car, but I drove it like a grandma. That is the best way to increase your gas milage. I don't think I ever got that car over 1/4 throttle after I tried nailing it for the first time.