Little road trip today, and outstanding MPG

I finished my chores early this afternoon so I was allowed to go "play trucks" for a while lol.

I went for a drive to a place called the "Lookoff" and to make a quick visit to a friend that has a bunch of old Ford trucks.
It was 238km round trip, or 148 miles back to the gas station. Fill-up took 29.66 liters (@1.35/L, cough), or 7.835 US Gallons. According to my iPhone, that's 18.9 mpg. I wasn't even trying to get good mileage...I was running a pretty steady 70 mph for the majority of the trip. My AFR was not even reading super lean or anything. Whenever I thought to look at it, it was usually oscillating between 13.6-14.1, in that area. I do have a fresh front end alignment, tire rotation and all tires set perfectly to 28psi.

The Lookoff is nothing to special, but it's one of those places where you can see for miles and miles. Nice view, and there's a little ice cream shack there, etc. Common destination for car cruises.



What effect does the weather have on AFR with a carburetor? I clearly remembering being able to hit 14.7 AFR with ease before, but this week I can barely seem to crack 14 most of the time. It's warm and humid though...maybe I'm thinking back to when it was cold and dry? Just curious. Not that it matters much. I sometimes think I should swap the stock size #66 jets back in there (it has #68's in it now), but I remember the AFR being pretty close previously.

I suppose my air filter could be dirty, but I can't imagine...it doesn't have that many miles on it. I checked the flapper valves in my dual snorkel 5.0 intake, and they're both wide open when hot.

Maybe I should finally install the outside air intake ducting lol.

That's all. Just rambling on a Sunday evening, and very pleased with my mileage. Maybe 20 mpg IS possible...probably easy with tunable EFI.

Nice view! Great MPG!

Wonderful view, and a great shot of a beautiful truck.  

Yes, that is great MPG.  As for the AFR, the hotter the inlet air temp the richer it gets.  And since it is hotter outside than before, it'll be much hotter under the hood and the radiator is having to work harder.  So yes, you should install the cold air ducting.  

Gary Lewis wrote

Wonderful view, and a great shot of a beautiful truck.  

Yes, that is great MPG.  As for the AFR, the hotter the inlet air temp the richer it gets.  And since it is hotter outside than before, it'll be much hotter under the hood and the radiator is having to work harder.  So yes, you should install the cold air ducting.  

X2 what Gary said.

I also run a AFR gauge and do see it running richer when it gets hotter out.
Remember colder the air the denser it is so more air packed into the holes with the same amount of fuel will make it run leaner.

My 300 also runs in about that same range of mid 13's to low 14's.
I have been thinking of leaning it out a little more, adjust the rod / seat, but it is running so good I hate to pull the carb apart and have it run bad. Maybe one day?
Oh I am pulling cool air from in front of the support.
I should check if the flapper valve is open all the way someday?

Being you brought it up did you ever get a MPG with the 4x4 truck the short time you had it on the road?
Dave ----

That's fantastic.  And the best my SHO ever got was 17 lol

In my normal driving, which consists of 11 miles to work and 11 miles back, with a few miles to get lunch and back, I get 10 - 11.6 mpg.  BUt there is no more than 5 miles before the start/stop starts.  I do wonder what it would get out on the open highway.   Probably imprve a bit, especially if it were on flat 55 mph highway.  302 with M5-OD r2, not sure of gearing.  

13-14 is awesome to me.   I do try to drive truck about 60 - 100 miles every week, which keeps everything working well.  I usually put gas in once a week or so, to keep it fresh.  

Great looking truck! It's just like mine, except... nice.

Nice, thats the kind of highway miliage I am trying to shoot for with my Sniper in my flareside.  Hopeful for 18 - 20 mpg highway at 70-75 mph.  Currently I get 16 mpg highway at 65 mph with carb, under powered smog engine, oversized 31x10.50-15 tires and a 2.75:1 axle ratio.

I owe the mileage to the 5spd trans and 3.08 rear diff. I'm running wide 275/60-15 tires, but they're the exact same OD as the stock sized 215/75-15 tires. My speedometer is very accurate, so that makes my calculations even easier. I usually double check the actual distance driven, but it's always the same anyway.

I had hoped to hit 20mpg with the truck after it was all broken in (10k+ miles on it now), and I'm sure I could do it...and likely even better with the EFI.

In 5th gear, 70mph is only 2000 RPM. That is just at the beginning of my power band. It's still a bit sluggish at even 1800 RPM, but at 2000 RPM is just winding up and I can climb hills with it like that.

I have to be careful not to speed with it...

Nice lookin' truck.....

Rembrant wrote

I owe the mileage to the 5spd trans and 3.08 rear diff. I'm running wide 275/60-15 tires, but they're the exact same OD as the stock sized 215/75-15 tires. My speedometer is very accurate, so that makes my calculations even easier. I usually double check the actual distance driven, but it's always the same anyway.

I had hoped to hit 20mpg with the truck after it was all broken in (10k+ miles on it now), and I'm sure I could do it...and likely even better with the EFI.

In 5th gear, 70mph is only 2000 RPM. That is just at the beginning of my power band. It's still a bit sluggish at even 1800 RPM, but at 2000 RPM is just winding up and I can climb hills with it like that.

I have to be careful not to speed with it...

Yep 5 spd with a 3.08 will help for economy long as you dont lug the engine down too much.

Im looking at going 3.25:1 axle ratio but may have to run 3.00:1 if the C6 im going to have built has too much slippage.  Im banking on 3-5% slip so I can run 3.25:1 axle ratio which would put me at 2.96:1 I think it is after accounting for the taller than stock 31x10.50-15 tires.  This should in theory put me between 2,400 - 3,000 rpm for 65 - 75 mph.

But in your case if your engine isnt lugging too much at those rpm then I say go for it cause it will help your economy.  Ideally I want 20 mpg highway but realistically I dont know if I could get 20 mpg but maybe I will be surprised after I get everything to where I want it.