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Excessive fuel consumption '71 Dauntless.

D

Dana44

Member
Joined
Aug 30, 2026
I think my cj has a drinking problem based on the 15 gallons I have put in the tank. All our driving is off road, so mpg do not work. However, I would say we have driven this jeep 30 miles. Lets go crazy and call it 60 miles. Even taking into account consumption differences while going really slow on a moderate trail, it seems like there should be better efficiency.
I am new to the 225 oddfire, and 2 jet carb. The previous owner did say he re-jetted it for our elevations in Colorado.
Thoughts?
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More data needed. You did not provide any real quantifiable data. Mine might get 2mpg if i drive it to work and back for a week... most of it simply leaks out.
 
I drove my 48 on some high elevation Colorado trails last week on the Fall Color Tour. It has the 225 oddfire, was in low range 4WD on trail. It has Teralow gearing in TC, with 5:38 axles, so it is low geared. Longest trail ride I went on was about 75 miles round trip. I was running low after we got off trail and added 5 gal of fuel when we were heading back to the ranch, but only used 12 gal total.

I don't know what your gearing is, but not likely to be lower than mine, so yes something isn't right, and like Joe says we need more information to be able to help.

"The previous owner did say he re-jetted it for our elevations in Colorado" This statement indicates you are relying on what the previous owner said, but it is going to take more than that to get it tuned for elevation. Mine ran fine in the valleys, but kept flooding out and stalling on the first trail ride I took it on once we got close to about 10,000 feet elevation. Some tuning on trail got it running good enough for the trip back down, and back at the ranch proper tuning with a vacuum gauge got the timing and fuel mixture right so it ran great the rest of the week.
 
Oldpappy said:
Mine ran fine in the valleys, but kept flooding out and stalling on the first trail ride I took it on once we got close to about 10,000 feet elevation. Some tuning on trail got it running good enough for the trip back down, and back at the ranch proper tuning with a vacuum gauge got the timing and fuel mixture right so it ran great the rest of the week.
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I'm really glad to hear you got to enjoy it out there.
 
Thanks. I am only now getting to enjoy this Jeep. I bought it two years ago, and have had to rework / rebuild a lot of things that were done wrong. I didn't enjoy the ride up that first trail, particularly when it stalled on a tight switch back with the front wheels against a ledge, and the back wheels about 3 feet from a very long drop, I didn't catch as much air as you did bouncing over that ledge on the Missouri trail, but did leap enough to scare my passengers. It was fun coming back down with it running better. Where I live is about 800 feet elevation, and you can't tune one here, and expect it to run well up there in the thin air. I should have tuned it on Sunday, but was busy cooking Dutch Oven fruit cobblers for over 100 people, while they went on the shakedown tour. I thought it was running good enough, but know better now.
 
its not apples to apples but this might help you. I drive my CJ5 to work regularly, 10 miles mostly highway each direction and have been keeping track of the mileage. I am averaging 11.3mpg. Usually adding 6.5-7 gallons to my 11 gallon fuel tank at each fill up. 225, single barrel Rochester, 3 speed T90 with Over-Drive and new 33x10.5R15's. I am at sea-level.
 
I get between 10 & 12 MPG with mine running with 4WD. I can approach 14 MPG running on slower highways. I comfortably run about 120 miles on my 15-gallon tank with 33s', 4:88s and no OD.
I have run my 2G Dauntless powered CJ for 20 years now and NEVER re-jetted. I run elevations from 1,500' to 13,000' Sure, there may be some performance loss in the high mountains, but it's minimal and to be expected.
 
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On the Rubicon run last June, lots of members were on fumes or completely ran out of fuel. I have a 231 v6, 5:38 and sm420, and I only had 2 gallons left of 21 gallons I started with to drive 22 miles of trail. I shut off at every opportunity, and still ran it close. Next year, I’ll have another 3 gallons with me.
 
I know it is a different jeep but my AMC 304 would get about 16-17 on hwy and some trail mix here in the east at elevations of 1000 to 3000 ft and occasionally up to 5000 feet, In the west in a mix of trail and highway up to around 9000 feet about 14 -15 mpg.
Never did notice any problems other than power loss up at 12-14000 feet with factory jetting.
 
Nice to see the numbers being posted for mpg. My all stock Jeep with the Dauntless and 4.88’s (stock tire height, no OD) gets between 10-14mpg with the Rochester 2G with #51 for the jets.
 
Mine has a 4.3 with 4.27s and overdrive. At 70mph it gets 10mpg. When I flat tow it at 75mph the 375hp tow vehicle gets 15mpg.

When I drove it with a 4cyl 5.38 gears it got an all time high of 16mpg towing a trailer with my snowplow on the interstate from NY state to Missouri at 55mph

My 4.3 is warmed over and my jeep is heavier than most but it is an exponential decay in mpg above 45mph.
 
Where you live can make a huge difference. Plain states might get 15 easy. Here in Western Washington where our little hills would be called a mountain east of Colorado it goes down fast. A stock four cylinder cant really even be driven here as it simply cannot go up our hills at any speed. Quite rare to find stock powered Jeeps here because of that too. Here any AMC v8 will struggle to get ten with 401s averaging about 7.
 
Oldpappy said:
I drove my 48 on some high elevation Colorado trails last week on the Fall Color Tour. It has the 225 oddfire, was in low range 4WD on trail. It has Teralow gearing in TC, with 5:38 axles, so it is low geared. Longest trail ride I went on was about 75 miles round trip. I was running low after we got off trail and added 5 gal of fuel when we were heading back to the ranch, but only used 12 gal total.
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Thanks everyone for the advise and the above confirms what I thought. I will go through the fuel system and get it figured out, which given my current schedule might be this winter.
 
134L souped up a bit T-90 30% OD D-18 5.38's 28.5" tires at 5050lbs total towing my little trailer at 60mph on mostly level ground (Interstate 5 Salem to Sutherlin OR) I got 18.4mpg Off trail as much as 5000 ft above where the carb was tuned for I got 11mpg with speeds all under 20mph. Lots of running in 2 low 1st and 2nd gear. I was running very rich due to the altitude. No trailer off road so weight was about 4100lbs total. My jeep has a framed insulated Aluminum hardtop.
 
I was always surprised by the fuel consumption in 4WD odd road. It always can be better of course, I am not judge.
In France the fuel price has so much increased that I am happy not to have my CJ5 ! :p:madwife:
 
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