I thought it would be fun to see what year, engine, carburetor, and MPG your cars get.
Here’s mine:
1968 Cougar 289 4V (Edelbrock intake and Carburetor)
12.88 MPG, Costco 93 Octane (I can’t lie, I wasn’t exactly driving to conserve fuel!)
Incidentally, that is darn near exactly what my 7,000 lb 2004 F-150 5.4 Litre gets. I did put a K&N air filter in the F-150 a month or so ago and mileage improved by at least 1/2 MPG bringing it up to over 13!
My '69 will get 17mpg on the highway with the a/c on.
1970 Cougar, 428scj (3.91gears), 4-speed. Factory intake and carb (w/factory jets).
I’m getting between 8 and 10mpg (depending on how heavy my foot is) on non-ethanol premium.
I’ve gotten 15 MPG with Isabel, 3.25 differential gears. With the TKO600 I recently installed, expecting considerably more (assuming some highway miles).
I’m getting pretty consistently 13-14MPG on low octane Costco fuel. Mostly city driving. It’s fun to see what others are getting.
302 stock
Auto trans
2V Carb
351C 4V with Holley 80457S carb and Offenhauser dual port intake manifold. Pertronix ignitor, 3.25 traction lock differential and 1989 AOD transmission. 14-15 mpg around town and 19-20 mpg on the highway at 70 mph with the a/c blowing.
My 68 XR7 390 has a Holley 700 cfm double pumper, Edelbrock Steetmaster intake and 428 CJ heads. I was told I have 3:55 traction lock. When tuned right I might get 9 mpg if I baby it. But I wouldn’t know for sure, because I don’t baby it! Gotta go now, I need to get gas. 
Best mileage I ever got with my stock 289-2V, C4 automatic, 3.00 open rear '68 was 21 mpg on the highway. Maybe that was on a downhill leg of my journey to Oregon. The rest of the time it was around 18 highway. City driving was more like 14 if I remember correctly. Will be interested to see if there’s any difference with the same, now rebuilt engine, now that it’s balanced, different cam, but same heads, intake and Autolite 2100.
To baby it is just not manly! These Cougars were meant to put our foots into! 
Oh, but drive responsibly! 
Grant,
I’ll be filling her up soon. 173 miles on the tank so far. I’ll post up after.
1970 351W 2V / FMX 3.0: 14¼-15 MPG in town, 18 on highway. Octane 89-91.
Mom’s (now nephew’s) '67 289 4bbl: 15-16 around town, 18 on a trip.
Dad’s (now my) 428: 9-10 in town, 15 hwy. 91 octane (all you can get in Cali.)
Just filled her up this AM. 14+ MPG
390 4V 4speed wide ratio.
It’s a mix of city/highway/spirited driving.
1969 Mercury Cougar Eliminator detailed fuel economy review
http://www.automobile-catalog.com/economy/1969/1835630/mercury_cougar_eliminator.html
Stumbled on this today at lunch while browsing around for Eliminator p0rn and though folks might find it mildly interesting.
Edit: wow, if you go to thier home page you can dial up fuel economy and performance specs on just about any cougar you want. I know it is all “computer calculated estimations”, but still… very cool 
I’m currently browsing their performance calculations for a 428cj drag pak 4-speed ram-air. 6 sec 0-60… not too shabby! Not quite as good as the super drag pak though (5.9sec).
The best I have gotten was about 4 or 5, on 100 octane unleaded with a QFT Q750 carb on a 351C. I get around 80 miles per tank.
It took a little less than one tank to drive from Carlisle, Penn to North Adams, Mass which is about 360 miles. I didn’t top off when I got home to find out the amount used. The combo is a 351w 2v, AOD, 3.50 gear in a 69 Cougar.
I used to get around 18mpg on the highway with FirstCat - my long-gone '72 Standard Cougar - with a bone-stock 351C-2V/FMX/2.75. The car was only used for going back and forth between home in Cleveland and college at Ohio State in Columbus.
Alpha- and BetaCats (both 351C-4Vs) didn’t do as well, especially after I tinkered with them and made them quicker and with 3.70 rear gears. Maybe 11mpg on a good day, but many smiles per gallon when I put my foot in it.
If I keep the Q-cats, they’ll probably get a transplant from my Crown Vic - the almost 500hp 393W/WR-AOD/3.70-ish gears. Even in the 4000-pound Vic it gets 15+mpg. Gotta love the overdrive trans!
On a cross country trip from Seattle,Wa to Columbus, Oh. I averaged 21 mpg. '68 302 4bbl, c-4, 3.00 open diff. The only thing that isn’t stock is the Summit brand street/strip carb which is a really awesome piece by the way.