Hmm interesting, I know I have popular mechanic magazine, I saw one ad and talked about 1983 F150 4.9L I6 with 4 speeds manual gets 16 in the city and 30 in the highway. ??? Did anyone ever seen that before??? Will try to find my magazine and will scan the copy and post it on here.

 

EPA testing methods were much different then and that was before the advent of gasohol [10% blend].

 

Gasohol was invented in the '70s as an answer to the 1973 oil embargo and later the 1979 energy crisis. Mostly known by ethanol now.

So was EPA testing of MPG an "invent" of the 73/79 crisis.

My 1981 owners manual states that it is rated, and can use up to 10% Gasohol, but if any drivability problems to discontinue use.

The EPA testing was at 48 MPH on a dyno. This was supposed to be the average mean MPH that people drove. This was during the 55 mph legal limit imposed in the '70s. Again because of the 1973/1979 oil crisis'.

Why these trucks get their best mileage at 55 mph. How many people drive 55 mph let alone 48?

 

I have a 1986 F150 with 4.9L and SROD with 3.08LS and 215/75 X 15 tires and drive like there is an egg between my shoe and the gas pedal. I have a 12 mile urban drive to and from work [many stop signs, traffic lights and then ~7 miles of farm land @ 45 mph]. I drive the same route with very consistent results and record my mileage.

It just so happens that I have the last 4 receipts in my wallet and they are as follows: 16.24, 17.16, 17.39 & 17.58 mpg.

On a recent somewhat hilly trip @ 55-60 MPH, it returned 22+ mpg.

I thought I might need to add that this is with Duraspark 2 ignition conversion and Carter YF from a 1970 F350. I should have mentioned that earlier. Sorry!

 

That's outstanding gas mileage '86F150Six!

If only 30 MPG was attainable with these trucks/motors.

I laugh just thinking about 30 mpg.

 

The most mileage I've ever got was 24 MPG. This is completely flat driving at 55 MPH, and is not the normal driving conditions I usually drive. My friend with the same identicle configuration as my truck, except for a clark (tremec) 4-OD, claimed he got 28 MPG in the same trip.

This was before ethanol, "Gasohol" became the norm in gasoline though. Didn't say ethanol wouldn't reduce mileage, it will. Just meant to say it's been around alot longer than some people might realise.

Mine averages 18-21 MPG at the moment. 300-6, feedback carb, T-18, 2.75 gears.

I have noticed that the mileage can change drasticly depending on fill up, and retailer. Change 5 to 7 MPGs just because of a fill up, using the same brand of gasoline.

Wish pure quality gasoline was a sure thing at the pump. Even a guarentee of only 10% would be nice. I know some stations add more...

 

The sellers or mixers also change the fuel formulations depending upon season, with "summer mixes" versus "winter mixes", whatever that means. It must have an effect.

 

Summer blends are not as volatile, meaning they don't evaporate as easily or at the same temp.

 

Sounds to me like they water it down for summer... coincidentally when travel by automobile starts to peak and gas sales go up. Hmm... thinning out the gas so they don't have to sell as much and make more profit perhaps?

Those are still some outstanding gas mileage figures for the 300 though! 24 mpg and a claimed 28! Jesus.

You fellas got me wanting to go read about gasoline summer and winter "blends". I'm going to go do that.

 

If you find anything interesting 1983F1503004x4, let us know...

 

I have a '79 with a 4.9l. I put a 4spdOD in it. It has 2.75 gears and in overdrive I'm barely running the engine Driving 60-65 I got 18mpg. That was with the truck filled with boxes, helping someone move. Nothing too heavy though, normal stuff. I'm sure I can get 20mpg out of it . . but I want to see the math on the guys claiming upper 20s If I stayed at 55 ( can't do it ) . . maybe a couple more . . maybe.

 

I don't worry about mileage, if I need gas I buy it.. I never let mine go below 3/4 tank

 

^^ I agree. But not letting your self go under 3/4 tank? Do you mean 1/4?


If you mean 3/4... you must fuel up often lol.


What I do, is when I get around half tank, I start "shopping around" for cheap fuel, and whereever I am, when I see a good price, I fill 'er up!

 

Fuel mileage is nothing but a personal game/achievement to me. Plenty of money to buy gas . . just like to be efficient. I have a lot of vehicles and each one has a "number" I try to achieve in as far as MPGs.

 

Better check 'em again, because...

13: Ford 9" rear axle / 2.75-1 (1977/82) / No Limited Slip.

17: Ford 9" rear axle / 3.25-1 (1966/77) / 2.47-1 (1981/86) / No Limited Slip.

FoMoCo changed axle codes/ratios more often than women change their minds!