MPG

  Normally the tire psi at 32 pounds of pressure ,any dead weight in the trunk some say keep the tank of gas half filled and a healthy engine is important .On the highway overdrive is nice . All torinos with 14 inch tires is the worse thing .The 15 or 16 inch will drive better and can give a mile on a gallon of gas . Get  tires with at least a 27 inch height like p225-70 R15 , or p235-60 R16 inch. They will not effect speedometer reading. Ford switch in 77-79 torino type bodies to 15 inch tires and a 2.50 axle ratio to increase mileage . You can use super instead of regular. Rear axle ratio, there is so much more, etc ,etc .Also driving habits.

Even my 460 equipped Cougar (Torino) gets 11-13 MPG driving "normally"

Meh, I track it in everything I drive

Engine wear is another big factor. My 75 that has (now dead) 351W got about 11MPG. That same car ten years ago got much higher (and I'm sure brand new it could have been as good as 16?)

So, when the 521 goes in, compared to the near-dead 351W (230,000 miles), I doubt I will see much of a MPG difference. And I do drive like a grandfather.

My 66 Chrysler 300 (383 4V engine) got 14MPG on the freeway Spokane-Seattle last summer. Not tuned up, distributor is worn out (misses real bad) and the carb needs a rebuild (but the engine is new with only about 7,000 miles from a reputable engine builder).  I'm thinking an electronic distributor, rebuilt (or E-brock) carb should help out tons. The distributor was in such bad shape (shaft wobble I believe) that when I went to tune it up (new points, cap & rotor, plug wires, plugs) that I made it worse (the missing). I'm not a pro at points, but I was careful. And I think my MPG actually went down in it!

The 71 F-250 gets about 8MPG around town. Highway is all about how fast you drive - with 4.10's and wind (like I did one time to Spokane) I can get less than 6 at 70+ MPH. I'm figuring with the rebuilt heads and the other improvements that my mileage will increase dramatically, even with the 4.10's.

Here is a photo of a 66 Chrysler 300 that I took at a car show a number of years ago:

I track my mileage in the Titan for business trip reimbursement, and the others I track for the fun of it.

Titan - 9-10 city, 14 highway (best ever was 16) Awful!
Civic - 38 city, 48 highway (no power anything) Sweet!
F100 - 16 city, 19 highway (lean engine/highway gear) Slug on takeoff!
Torino - 15 city, 17 highway (found old log book from '83) lean/gearing
Boulevard - 44 whatever
Wrangler - 14 city, 15 highway (just moving more air)
Cherokee - 17 city, 21 highway
Bronco II - 19 city, 24 highway (regular tires/granny driving/5 speed)

I have found that most vehicles like a larger tire/wheel combo up to a certain point, but in the case of the Cherokee, Bronco II and F100, the closer you stay to a stock diameter, the better they perform and reward you with better mileage. On my 5 speeds, I shift at 2,000 rpm and try to get in 5th asap (taking care to not lug it), automatics I feather the throttle. The Civic is a high effiency model with no options except radio and air, so it is not an accurate rep of what they normally get, and the Titan is a hoss that will pass anything but a gas station. Those two are oddities, and the F100 is just a weird combo 302/fast shifting FMX/2.47 gear) that is an absolute slug off the line but will cruise at 60 turning 1,400 rpm.

I guess what I am getting at is that there are ways to optimize your mileage that will also reward you with better performance - up to a point. Once that equalizing point is attained, then going foward with measures to get that last highway mpg will affect the performance of the vehicle and force you to compromise. It is your decision.

Gearing, tire pressure, fuel optimization, weight, and aerodynamic drag all interact to help (or hinder) the goal of better performance and efficiency.

change the cam/cam timing. stock cams aren't optimised for the low gears they stuck in the rears, they're a compromise and set retarded (the effort of the day to reduce tailpipe emissions). the engine is lugging under 85mph and not even close to efficient unless you're sailin down the highway 

Edited by Rockatansky - 19-May-2011 at 7:22AM

255DEH and 265DEH really shine in pickups, too. I would most certainly choose a 265DEH for my 351C if I ever need to build it up. Could be what's in there now for all I know but I was told it's an Erson RV cam. So not CompCams allegedly. At some point I may change out the timing set for a mild sounding gear drive just to scare off the ricers. Maybe I'll be able to read some numbers on the cam and know exactly what I have.

i know, but it should perform better with a 3.79, or higher, even for mpg