Fuel economy

[melford1972]

As some have already said, EFI will not net you much increase in MPG. I was expecting a slight increase when I fuel injected my 72 Wag. And there really was not really any notable difference. Tire size/pressure matter.

Has anyone ever tried Hypermiling in an FSJ?

['89_Wagon]

I'm trying to think of how to hypermile in an FSJ? Aero mods? Coast in neutral? Really high tire pressure?

BTW, I don't recommend any of this....

[rang-a-stang]

I am currently tuning my mazda for E85. You lose about 10 percent MPG but in my area it is almost half the cost of 91 octane. So even with the loss in MPG, my fuel costs are still significantly less.

If I were keeping my chief it would be transitioning over to E85 when My mazda was done.

[rang-a-stang]

... those changes netted about 2-3 MPG. ...

Don't lose the forrest through the trees here! That's a 20-30% increase from 10MPG! That's amazing!

larger/wider tires will kill mpg
efi netted me several mpg(3-4) city driving after tuning
efi gains maybe 1mpg hwy driving if that
the lack of 4spd and zero aerodynamics make these things gas pigs

...IMO aerodynamics is the main thing these Jeeps lack for better mileage. This goes along with the big tires and wheels reducing mileage, partly from rolling resistance and partly from a larger profile in the wind. Modern design optimizes every surface and edge in the vehicle for less drag. Also, drag goes like the square of velocity, thus the speed you drive make a big difference in mileage when your vehicle has such poor aerodynamics.

This. Our rigs are as aerodynamic as a barn. At freeway speed, you need so much power just to keep that beast going, it is going to drink gas. I rarely go over 65 in my turd. My turd's sweet spot is 55 but 55 on SoCal Freeways is asking for a wreck. They also weight 4500#s. You need a lot of power to get that much barn shaped American Truck moving from a stop (hence terrible around town gas mileage, too).

I think Headers, a high flow cat(s), and a good 3" exhaust will also make a marked increase in MPG...if you drive it the same. Problem is you will want to stick your foot deeper in it because it will be way more fun to drive and will sound like a ticked off animal.

I'm trying to think of how to hypermile in an FSJ? Aero mods? Coast in neutral? Really high tire pressure?

BTW, I don't recommend any of this....

I used to have a '91 Geo Metro XFi (I loved and miss that car BTW, not because I got 45MPG out of EVERY tank no matter how I drove it but because it was a fun little death trap to drive) and I was pretty active on their forums. Of course those forums are chok-fulla hypermilage stuff. One time a guy on the forum asked "How do I make my Metro Fast". Some crusty Metro dude had an epic response. It went something like this:

It's Easy! Remove gas cap, replace car, install gas cap. If you want to go fast you bought the wrong car. Getting a Metro to go fast is like buying an old F250 and trying to get great gas mileage.

I think that statement can go the other way, too. To hypermile a FSJ is like trying to get a Prius to turn 12s in the quarter. Sure you can do it but the juice will not be worth the squeeze.

[letank]

I am currently tuning my mazda for E85. You lose about 10 percent MPG but in my area it is almost half the cost of 91 octane. So even with the loss in MPG, my fuel costs are still significantly less.

any good site... the kids have a spare 99 prot

[stonybrookpictures]

79 Wagoneer MPG

AMC 401, Quadratrac, 35" tires, 65 Mile trip, 70 MPH, 10 Gallons on the dot.......

[sierrablue]

Daily driving the '71 I've been having similar thoughts, and here's what I've gathered from some driving and reading a bunch of forums and talking to family about it:

The top thing is driving style, of course. Easy acceleration to start with will do wonders for mileage. I've also started popping it into N on the way into town, and putting it back into gear around 30, 35 (3.50s, 225/75r15s, and an auto that happens to be about the point where the RPMs aren't much above idle). If your neutral starter safety switch is lined up right (or with a stick simply pushing the clutch in) you can shut it off and get every last bit of mileage out of it. Also aerodynamics start coming into play right around 60 mph, so keeping it right around 60 in top gear is the peak mileage point, especially with a brick like a FSJ. So 55-65 is generally the recommended cruising speed.

As far as carbs go, the Edelbrocks and Qjets (more the Qjets) tend to get the best mileage from what I can tell. The Edelbrock would probably be the way to go with that manifold; it's easier to tune and already square bore. The advantage of the Qjet is that it has smaller primaries, and thus smaller venturies, which increases the pressure and thus makes for better metering. But the Edelbrocks still have metering rods and with the tuning kit it's pretty easy to get them dialed in. I just put a Qjet on and am working out the kinks...we'll see if it does any better for mileage than the Edelbrock did. But on my intake it's supposed to have a Qjet because it's a Buick 4-barrel.

Trannies tend to be expensive and need adapters for these rigs, but if you get a 5-speed in there, you can short shift it, the clutch allows zero slip (if it's good and let out), and they're lighter than an automatic.

The other thing I didn't see listed here was aero. I know these are massive bricks, but little things can help. Air dams are pretty easy to make if you don't have one, and those can help. Removing roof racks (a non-issue on J trucks)(well, most of them), big clunky mirrors, spoilers, and blocking off holes in the grille you don't need for cooling will also help the air go around the Jeep, thus allowing cleaner flow and less resistance. Other things that could potentially help with flow; all season tires (rather than the very square all-terrains), and theoretically keeping it washed and waxed can help...not sure how much that is helpful and how much people just like their rigs to look pretty, but there's that.

I've read that with the AMC V8s the 401s actually tend to get better mileage than the 360s. The '88 with 3.50s, 31"s, and the .060" over 401, headers, 3" exhaust (2.5" Y-pipe), and TBI would pull 18 on the first half of the tank, and about 12 on the second half, averaging about 15. I know, you said that's not the route you're planning on going at this point, but...

Oh, if you're running oversized tires and the speedo if off, you also need to add the 10% or so to the number of miles indicated, so you may be pulling better mileage than you think.

Currently I'm trying to smooth out my driving, utilize N a lot, etc. I'm getting a vaucuum gauge, too, so I'll be able to see how I'm sitting at cruise and good feel for my mileage at any given point. I found last year that more timing got me better mileage, too. But I'm running 3.50s and 225/75s as previously mentioned, with locking hubs. I also have the roof rack on, and I actually opted to stick with my heavy steel wheels. While they're harder to get rolling, once they're rolling they have more momentum (and it's not a dead weight; it's a spinning weight), and they allow me to run hubcaps that flow the air more cleanly. Other things affecting mileage for me is winter gas and cold temps (we're finally getting there though). Between it getting warmer and being smoother I went from lower 12s tops to upper 13s, and I could still be smoother. The last tank was 12.77 something, but then I spent a lot of time not going anywhere trying to dial in the Qjet. If I take the time and seal up my gas tank it'll probably go up too...60 is right around 26-2700 RPMs for me. Anyway sorry for the book. Hopefully it's a helpful book, at least.

I'm probably the only one, but I've been wanting to do an EV conversion on one of these...I've figured out how to get a reasonable setup for under $20 grand, which sounds like a lot, but in purely oil and gasoline (averaging $3.50 a gallon and 12,000 miles a year) it should pay off in less than 5 years. Plus no maintenance and all of that good stuff

[timwiller]

holy grail of mpg??

my little 304 with t-18, 60mph, no headwind = 10mpg.


...try to drive downhill a lot.

['89_Wagon]

SierraBlue, it's impressive your '71 is your daily! Way to go!

That's a lot of work to save on gas and if prices go down again.... that $20k swap cost break even point will stretch out a few more years. Better to spend $5k or less on a manual civic hatchback from the early 2000's or other small car with a manual. You'll get you money back far faster with one of those. My wife was able to squeak 50-60 mpg on a regular basis from one of those last time gas was $4 a gallon.

Now, if you want to do the EV swap for fun, totally fine by me.

Also, just to nick-pick... you need to factor in the cost of electricity for the EV conversion... which the Wag will use A LOT of. There's no way around it... it takes a lot of energy to get our FSJs moving and keep them moving.

[sierrablue]

SierraBlue, it's impressive your '71 is your daily! Way to go!

That's a lot of work to save on gas and if prices go down again.... that $20k swap cost break even point will stretch out a few more years. Better to spend $5k or less on a manual civic hatchback from the early 2000's or other small car with a manual. You'll get you money back far faster with one of those. My wife was able to squeak 50-60 mpg on a regular basis from one of those last time gas was $4 a gallon.

Now, if you want to do the EV swap for fun, totally fine by me.

Also, just to nick-pick... you need to factor in the cost of electricity for the EV conversion... which the Wag will use A LOT of. There's no way around it... it takes a lot of energy to get our FSJs moving and keep them moving.

Thanks It's not perfect, but it'll get me anywhere I need to go, any time of year, and still beat a lot of new stuff of cars off the line...but hey we're talking mileage here And to be fair, it's from OR, so little to no rust (and PO resprayed it), and I've replaced some part of pretty much everything related to the engine.

I know, not the best EV conversion. I mean, the ultimate EV is something like a GT40; light and extremely aerodynamic, but designed for some level of structure (I mean, 427 big block...). But much like everyone on here, there's a certain draw to these rigs, and they're so practical (minus maintenance $). And it's super capable; with the all seasons and no lift I can get it pretty much anywhere without damaging the body, and also without getting stuck. I realize it's not the best canidate, but I could do a lot worse too. So I totally get it, and I don't anticipate anyone else on here going that way, but hey, every last bit counts. I will also say that gas prices were slowly on their way up before Russia made their move...so even if they're back down to $3.50 when things settle back down, we don't have an unlimited oil supply and we can't plan on the prices going down much again. Just my .02 though.

Sorry Chad, didn't mean to hyjack the thread or anything. One other thing to help mileage is a vacuum/"ecogauge" as Bosch labeled it. It shows you when you're on the gas really hard and might not know it, so it helps some if you pay some attention to it.

[mrtazwrench]

Not a big deal, I just know I'm not going EV as my J20 is just a summertime toy. I do have a Wagoneer with an LS in progress I just need to get back on that and push to get it done.

[backroadin']

I second the qjet, great carb for economy with the small primariies and vacuum secondaries. I would at least go with a carb with vacuum secondaries.

Good tire pressure. I went from 32 bfg at's to 33 mud terrains and lost about 2 mpg or so. It's not my DD, so I was going for looks.

Install manual hubs if you don't already have them.

If I was to spend any money on trying to get better mileage, besides the carb I'd probably change to 4.10's if you're set on those tires. A tranny swap would be spending too many dollars to save pennies, but if you did the gear swap yourself, it'd be less dollars. Don't go freeway speeds and drive by the tach and vacuum gauge.

[sierrablue]

I ran into one more thing with mileage here, I'm not sure how interested you guys are.

I discovered about a week and a half ago that my left front brake caliper was dragging. When I pulled the wheel, I discovered that the caliper wasn't free to move--if I stepped on the brakes, I literally could not make the rotor turn by hand (after lifting off). I had to break it loose with a mallet, and even then it was clearly too tight. Taking it apart, I discovered that the bushings couldn't move freely within the caliper. I wound up pressing them out, and cleaning the bushing surfaces, as well as the corresponding rubber insulators, using steel wool. Then using one of the bolts that holds the caliper on, I put axle grease on those surfaces once they were cleaned. I put everything back together, and on the last tank I pulled 15.23 mpg, still on winter gas I'm pretty sure. And I was harder on it than I'd been trying to be, so I was expecting somewhere in the 13s. So check your brakes, make sure they can move properly, and make sure the rears are still in alignment. One more thing to keep in mind, that will make a big difference.

[babywag]

caliper kits are like $5
gets a guy new bushings/pins/etc.
rarely replaced during brake jobs but is required imho

[FSJunkie]

Mine gets 11 mpg at 75 mph and 14 mpg at 65 mph. That tells you the whole story right there. It tells you that the biggest reason fuel economy sucks in these Jeeps is their aerodynamics. They fight the wind and the faster you go the worse it is.

Want to save gas? Drive 55 mph.

How much gas can you buy with the amount of money that it would take to modify the Jeep for better fuel economy? It would only be marginally better fuel economy at that.