Gas Mileage?

[Scout1067]

I have been running an experiment lately trying to figure out what the actual mileage I get from my 81 CJ7 is. Mine has the AMC 258 i6 / 4.2l in it with an oem muffler. To that end I have a running spreadsheet that I put together and update every time I get gas. I do this mainly because my fuel gauge is not working, when it reads empty I still have half a tank of fuel in it when I fuel at the pump.

It doesn't help that the PO had the carb set to run as rich as possible without flooding the engine so I had to reset that, new spark plugs, route the PCV hose correctly etc. Essentially I am having as much fun with the CJ as I thought I would when I bought it 2 1/2 months ago.

I started out getting 17mpg and that sank to 14.8 at its lowest but as i fix things it has crept back up and yesterday my mileage for my last fill up was 23.96mpg. I don't see how I can get much better than that.

My next project is going to be going through the DAR on the fuel gauge to figure out what the issue is there because this country boy cannot stand having an inop fuel gauge.

Lastly, what kind of mileage do you guys get on your jeeps?

 

[Scorzany]

From my last fill up I calculated roughly 17.5 MPG. I'm good with that!

As for your fuel gauge, it might just be a grounding issue.

 

[Scout1067]

From my last fill up I calculated roughly 17.5 MPG. I'm good with that!

As for your fuel gauge, it might just be a grounding issue.

I ran through the DARS after I posted this and according to that at least, it is the sending unit. I guess I will live with it for now because I plan on replacing the tank and rewiring the whole jeep next spring.

 

[hole]

With the T-5 , 2:73 gears and 30" tires, the best I got was mid 20's at 60 mph
Now, with the T19, 2:73's and 32" tires the best I've seen at any speed is 17mpg and 15 is the norm

 

[jp360cj]

OP, what's your tire size and gear ratio? Is your speedometer accurate?

I've been using the Fuelly app to track mine since the last several fill ups. With the 360, 35s, and 4.10s, I got 7.3 mpg on my 1st tank, then found a caliper dragging. Got that fixed and the last 2 tanks have been 9.9 and 9.5 mpg around town driving. I've spot checked it in the past and it's been around 9-10 mpg for the most part.

The last few times I've taken it on a road trip (mostly 50-60mph), I got 11ish loaded down for a weekend. When I had the 3.73s and 33s I could get 15-16 mph on the highway. But It's picked up several hundred pounds since then (Winch, tire carrier, spare tire, 35s, T-18 , Dana 44 /9" combo).

 

[Belizean]

Mine has been bad from the start with approximately 19 in the early days. With about 240 K miles now, and in town driving it is mainly 16 mpg

 

[Scout1067]

OP, what's your tire size and gear ratio? Is your speedometer accurate?

I've been using the Fuelly app to track mine since the last several fill ups. With the 360, 35s, and 4.10s, I got 7.3 mpg on my 1st tank, then found a caliper dragging. Got that fixed and the last 2 tanks have been 9.9 and 9.5 mpg around town driving. I've spot checked it in the past and it's been around 9-10 mpg for the most part.

The last few times I've taken it on a road trip (mostly 50-60mph), I got 11ish loaded down for a weekend. When I had the 3.73s and 33s I could get 15-16 mph on the highway. But It's picked up several hundred pounds since then (Winch, tire carrier, spare tire, 35s, T-18 , Dana 44 /9" combo).

I have the OEM tranny and diffs in mine and 9.5x30 tires. My mileage actually fluctuates pretty wildly. I will get high mileage one fillup and terrible on the next while driving the same route to work and back. I think my rear diff needs a rebuild but I haven't gotten around to opening it up yet. It does make a godawfully loud noise when I get up around 45-50mph though.

 

[Hedgehog]

My CJ5 , 360 amc gets ~10 mpg doesn't matter what I do. I even switched from 3.73's to 3.31's and it doesn't make a darned bit of difference.

 

[Scout1067]

Fuel efficiency for my last three fill ups was 20.5, 19.3, and 20.5 mpg. I can live with that and to be honest it is way better than what i expected to get when bought it.

 

[Hedgehog]

For any CJ that is exceptional mileage, I'd be extremely happy if my CJ got above 15 mpg, above 20 would make me … I fail for words here, but leave it that 20 mpg is exceptional mileage.

 

[Lumpy Grits]

Flat ground I can get 16-17 mpg @ 65 mph at about 2600rpm in 5th.
It's a Jeep-Not a Prius.
LG

 

[buzzardB]

1979/ AMC 304 2 barrel stock running gear 11.5X32 tires gets 12 to 14 mpg mostly 55 mph highway (very small town). Varies I think because sometimes I notice I'm revving too high while letting the clutch out and/or not shifting to high gear (3rd) as soon as possible,or down shifting too soon.

I cover 0.9 miles on the odometer between mile marker signs on the highway, so I guess that means actual ground covered by my rig is 10% more than what the odometer shows. Soooo, I consider my real mpg is 10% more than stated above???

 

[Scout1067]

For any CJ that is exceptional mileage, I'd be extremely happy if my CJ got above 15 mpg, above 20 would make me … I fail for words here, but leave it that 20 mpg is exceptional mileage.

I have kind of a tic for trying to get the best gas mileage as possible out of my vehicles. I really only expected to get between 14-16mpg from my CJ and I am surprised myself with what I am getting. The test will be if the mileage stays the same over the long haul, especially with winter coming on and we tend to get quite a bit of snow in the part of Germany where I live. Heck, I am curious to see how well it starts in the cold. I could probably up it a little if I put street tires on but that would be a bridge too far for me. I still want to be able to take mine off road when I get the urge.

 

[gunsmoke]

I have a Weber 32/36 on my AMC 258 i6 / 4.2l . I spent 6 months tuning it since I didn’t know what I was doing. I’m now running 20.4 mpg consistently. 1976 CJ7 -T-18 -4.10-31x10.5 BFGoodrich AT

 

[Hedgehog]

Is that mileage using the stock uncalibrated odometer? I use a GPS unit to figure gas mileage.

 

[gunsmoke]

My speedo is accurate. Google maps shows me 32 miles from work. That’s exactly what the odometer puts out. I’ve had my wife drive past me while I tag it with a LIDAR too.

 

[mtnwhlr]

So you live in bailey my cousin is the Sheriff of Park County.

 

[gunsmoke]

Yeah. I live in Bailey. Park County is a cool little place to live.

 

[Scout1067]

I have a Weber 32/36 on my AMC 258 i6 / 4.2l . I spent 6 months tuning it since I didn’t know what I was doing. I’m now running 20.4 mpg consistently. 1976 CJ7 -T-18 -4.10-31x10.5 BFGoodrich AT

I have a Weber 32/36 on mine as well and spent the first 3-4 weeks after I bought it constantly making tiny adjustments because the PO not only had it adjusted wrong, he also had the PCV running into the air cleaner and the crankcase filter hole on the valve cover plugged with an oil filler cap.
I think I have hit the sweet spot on the adjustments now as I idle nice and smooth at about 800 RPM warm and it hts 1950 RPM at 60mph on the way to work.

 

[gunsmoke]

I think I was following your quest on tuning back when you first got started on your Weber. I think you had posted pictures of your PCV routing for advice. I could be wrong. I’m glad you got it figured out. I was ready to quit and go TBI because it was really whooping me good, but I stayed in the fight. I’d like to feel the difference between this carb and a 38