Fuel Economy

[71 Project 250]

My father I have a 240 cid L6 that we recently bought, and my father is thinking of using as a commuter (over a 7.3L Powerstroke). We were wondering if someone knew pretty well what they get in theirs. We certainly do appreciate it.

And to those who don't know, the 352 V8 gets around 8-10 with our three speed on the column.

[craftsman]

My 68 with 240 and 3 speed with 3.70 gears was getting 15mpg before i took it apart.

[Waller460]

prolly not any help, but my 65 falcon gets 25 with a 170 straight six

[smclaren]

I'm getting 15-16mpg on my 240 on LPG. Proberbly got slightly better on Premium Unleaded. And this really nursing the pedal.

I've lost 10-15% pick up grunt on LPG, but LPG is 70c per litre as opposed to $1.50 per litre for premium unleaded. $40 to fill the tank as opposed $85 - $90 ... no contest I'm afraid !

I must admit, when I first got my truck I was suprised that the 240ci didn't return better milage on petrol. I guess gas prices didn't mean anything when the engine was originaly designed. They are pretty gutless engine in stock form, so you got poke em to get em going, but crusie well on the highway. Getting them up and going is where you use the petrol I am guessing.

I have often wondered if a small V8 (302) would get better milage on an F-truck than a big straight 6? Theorectically they should !

Hope that helps

[binder56jd]

sm

same probs w/302

the fixes are engine/carb set up, trans & diff gearing

[Dragon]

240 6 with offy dual port manifold and 600 Holley 4V is a whole new beast. more torque more mileage and 3 seconds faster in the quarter.

[averagef250]

Seen quite a few bump F-100 2wd's get low 20's with a 240. They are gutless, but have never ceased to surprise me how much abuse they'll take.

[clemm17]

Depends on the engine and the truck. I have heard of stock ones getting as high as 22, in the 80s on older trucks. Newer 300s wernt as good! I am working on a very custom built 300 I6 for my 71' 4X4 crewcab truck. I expect to get a minimium of 18, but I have spent alot of time and money building it. This one is really built! I used to have a 76, that I just bolted on headers, and a clifford intake with a small 4bbl. I got 18 mpg out of it, hauling hay and logs. I also passed a friend I worked with, on a long steep hill. both of us had about the same load, our trucks were Identical execept tires and engine. He had 7.50 X 16, I ran 9,00 X 16 which gave me a slightly better gear ratio. He had a well built FE 390 with RV off road cam, I had a stock 300 with clifford intake headders and a 4bbl carb. I got 18 mpg he got 6 mpg. I waited at the gas station at the top of the hill while he poured more money in the gas tank!

[averagef250]

Not to call BS, because I've seen 300's do amazing things while getting great MPG, 18 MPG in a fullsize truck with a 300 inch gas engine up a grade with a good load is impossible at apprpriate A/F ratios.

The 300 can do things like that because it has an unbelievable ability to run rediculously lean and not melt down.

Basically what I'm saying is you can do that with a 300, but you're shooting yourself in the foot because eventually it will break ring lands and cook valves.

Everyone I've ever met who thought they had the "magic engine" that ran hard, pulled a load, but got great MPG eventually lost all their fuel savings in engine rebuild costs. A fullsize (6000 lb+) truck with a gas engine cannot get better than about 15 MPG for a running average of mixed driving. Older, less efficient engines are lucky to get 10 as an average. If you're getting better than that you're running your engine lean and it will be the death of it eventually.

[James]

I have a '71 F-100 that got about 13MPG with a 351W and my '94 F-150 gets about 16+ MPG with a 300-6

[edselehr]

I just took my '79 F250 crew cab on it's first camping trip. It has a 300 and NP435 4-speed. I was pulling a 16 foot camp trailer that weighed in at about 3000 lbs. I was getting double-digit mileage, which is fine, but the power was crappy. On the flats it was working to do 60mph...on moderate hills I had to quickly shift to third, and on steeper hills I was down to second. I understood when I got the 300 that it wasn't a zippy engine, but once it's moving why can't it keep moving? BTW it still has it's original one barrel, which I'm sure is part of the problem.