Mileage

[bmcgc]

I suspect that I am losing mileage through a hose into a gas can at night in my driveway.

1966 F100, long WB, 352/2V, 3 speed, 3.25 gears, 225-70-15 tires. oem manifolds, dual exhaust, open element air cleaner.

50/50 city/highway driving. On the highway Im doing 55, in the city 35-45.

Im getting right at 10mpg.

It seems a little low.

What say you?

[shocker998md]

I get 13-15 MPG on the highway no shit hand calculated. Put 18k on the truck last year and was deployed for 6 months of that time.

352 edelbrock performer intake and 600 cfm edelbrock carb, headers, duals, Rebuilt dizzy with petronix, 255/60/15s out back, 3.55 gears. Tune up was on point and ran timing at 12 initial and I think 36 total on 87 gas, 91 if I was towing or hot rodding.

My wife got 10-12 driving in town for the 6 months I was gone.


Only thing I could see is the 2V hurting you, but Id be looking at your tune.

[Gritsngumbo]

If you suspect, sounds like a job for "Locking Gas Cap".

[charliemccraney]

That is on the low end of what I would call normal. It's an old truck with an engine that's not terribly efficient, particularly if it is stock.

Is the 3.25 gear stock? It sounds pretty tall to me and if you go too tall, it can hurt your mileage as much as being too short and it makes it less fun to drive .

[bmcgc]

No tag on the diff, I got the 3.25 off the door tag.

Timing is set by ear.

The truck starts easily, even on cold days and is not cold blooded at all.

Miles on the truck and engine are unknown. There is a tag rivited to the block that says "reman by Ford".

Locking gas caps are ugly.

I have a .357, thats a more efective deterent IMO.

[ICEMAN6166]

I have a .357, thats a more efective deterent IMO.

agreed.

as to the mileage 10 is on the low end. i get 12-14 with my y block and 4.56 gears. if i go 55 and let everyone pass me i get 14, if i travel with traffic @70 it goes down.
you did not mention your ignition-points or electronic but with points as they begin to close up your mileage will drop off

[f100jim]

I get around 14 around home. Used to drive it to the beach( 180 mi one way) and get 18 driving 55 no faster with the camper shell on running 1990s premium 93 octane. 352 3 sp, 3.25 gear.

[donald luster]

take a perminant marker and put a mark on the cap at something that you can remember. Dont twist the cap on all the way. Then if it not where you set it then someone is getting your fuel

[62galxe]

A screwdriver, sheetmetal screw and a pair of channel locks and that locking cap is toast. They have the easiest to pull lock tumblers. My 292 only gets 13 on the highway and I have a overdrive trans.

[Toyz]

From what I've seen, Kenny and I have similar driving "styles"; probably better suited for electric propulsion; ie, like an electric switch, the accelerator is either on or off! 10 mpg is a little above my old norm, partly due to the 223, the aforementioned heavy foot, and somewhat larger and wider tires than OEM.
Unless you are dealing with a careful thief with remarkable restraint, or simply a leak, I would suspect the overnight loss would be more obvious than indicated by 10 mpg.
Paul.

[bmcgc]

They might have a small gas can.

Or they dont want to be obvious about it.

After I cleaned the carb and stopped the leaks, added the duals and dumped the oil bath, I was expecting 13-14mpg.

Ive got an HEI dizzy, but havent got around to doing anything about it yet.

[charliemccraney]

I really don't think anything is out of the ordinary with 10mpg. The problem is that you don't know what it was getting before so you just can't know how your changes have affected it. Cleaning a carb, adding dual exhaust and changing the filter housing is not necessarily a recipe for better mileage.

There was a post on fte, maybe even here a while back about mpg and 13-14 was actually higher than average. Ah, here you go. http://www.ford-trucks.com/forums/11438 ... leage.html In that particular post, roughly 73% of the people who responded get between 8 and 13mpg. If you search "mileage" and "mpg" other posts will come up and you will see that 10mpg is pretty ordinary.

Have you done any significant tuning with the carb, timing, initial, and the advance curve? If you are just going "by the book" with all of that, you are leaving something on the table.

However, if we assume 12mpg is about average, that does work out to about 2 gallons difference. I think the gas cap marking method mentioned above is a good place to start.

The HEI probably will help. When I converted and with some tweaking of the advance curve, I picked up 2 highway mpg.

[bmcgc]

According to the calculator, Im turning about 2600rpm at 65 mph.

If I went to a 235-75-15 and 2.79 gears, rpm would drop to 2100 at 65 mph.

I think the carb is part of the problem.

I have the 4v manifold off the 390, I would like to do a manifold, carb, HEI dizzy swap. Its a lot of work and its winter. Maybe next spring.

Ive still got to do the ps and disc brake swap.

[shocker998md]

Going to 2.79 will kill you in town.

My buddies galaxie that was 352 2v and a COM was a dog in town with 3.00s and 205 sized tires.

I have found if im going for mpg dont go over 60. But thats my setup.

[DV65CustomCab]

352, 3spd, high 2's or low 3's rear axle. All stock except dual exhaust on original manifolds and a Pertronix ignition. I get 15 pretty constantly, a little more on the highway.

[charliemccraney]

Save some dough and get overdrive, man. I get 16.5mpg at about 75mph. That's with a stroked,ported, cammed Y block. Overdrive is worth it and you don't loose your low end due to super tall gearing.
Before the overdrive, it was about 13.5 at the same road speed, about 3500rpm.
Whatever the case may be, throwing gearing alone at it is not the answer. You have to tune.

[Toyz]

According to the calculator, Im turning about 2600rpm at 65 mph.

If I went to a 235-75-15 and 2.79 gears, rpm would drop to 2100 at 65 mph.

I think the carb is part of the problem.

I have the 4v manifold off the 390, I would like to do a manifold, carb, HEI dizzy swap. Its a lot of work and its winter. Maybe next spring.

Ive still got to do the ps and disc brake swap.

You must like that "bulky" look; boat anchor intake, football-helmet sized distributor
A good two-plane aftermarket manifold can be obtained cheaply, and back surgery is NOT economical. As to the ignition , there are good magnetic and Hall-effect distributors which are in the price range of the HEI, and look more like they belong on a Ford: yes you'll need an external coil, and some type of control box if not a "ready to run". You can use a GM "module" if preferred; it's small enough to hide, and about as good as Duraspark or MSD for mileage purposes, IMO. With fuel economy your concern, you may want adjustable advance. The smaller sized Summit-branded carburetors are a good economy choice, and easily set up and tuned.
Everyone has their preferences; as Charlie said, fix the basics, make upgrades if preferred, fix the basics (again), then enjoy the all-around improvements!
('bout runnin' out)
Paul

[charliemccraney]

Here's a link to Bigmike's quest for better mileage from last year.

viewtopic.php?f=1&t=25146

[bmcgc]

I already own the HEI and the oem 4v manifold.

I havent seen a used aluminum FE intake for under $300.

[totten]

Mileage on my 66 is 300,cruiseamatic,3.00 gear is about 12.5 mpg. Gets better at lower speeds. Needs 4 speed automatic Tony