Gas mileage improvements?

My 98 is pretty much stock except for add one like a trans cooler. I drive to school and back every day and go through an 1/8 of a tank, which isn't terrible but when you factor in work and other stuff it's about 40 bucks a week. Is there anything cheap I can do to improve the mpg's?
I would LOVE to spend 40/wk for gas. If I wake up in the morning with less than $20 in my wallet I dont even think about starting my jeep. I get 11-13 mpg's around town and 16-18 hwy and everyday I put $20 in to drive it for the day. Ill see what happens after I change a few things. And how far are you driving to and from school? 40/wk is a amazing if you travel a good distance. My honda gets 362 miles to a 9gal tank, 18psi 402hp but it sucks as a daily since twin disc murders me in 5oclock traffic :/
 
I scored a new Airaid Intake on Craigslist for dirt cheap. I installed that and the DynoMax Cat-back at the same time. I also went ahead and replaced fluids and installed new plugs, wires, coil, and did an oil change.

So far, my mileage has improved. I believe I'm in the 15-17 mpg range. Much better than before when I was getting 11-12 mpg. I still believe I have an exhaust leak and I'm almost ready to go ahead and swap in a new Exhaust Manifold from Dorman. All in all, I'm quite pleased with the improvement in MPG and the more aggressive sounds coming from my XJ.
 
Current tank of gas I am doing 15.7 MPG stock 2000 with 235/70-16's. I got one of the monitors you plug into your OBDII port and it will tell me something like 39 different parameters for the engine. First tank I have used it own, I'll do the math when I fill up and see how close it is. Can't remember the brand but it was an introductory price of $60.
 
SO what about shell vs AM PM vs chevron? Then regular vs v power and such? Worth the extra money. I am getting under 10 MPG around town in the jeep I just built. Reading about the the brake caliper sticking reminded me that the jeep started pulling to the right recently. Im pretty sure the right caliper is dragging the whole time. Also have a leaky manifold... Suck in cold air and send misleading readings to the computer from the o2 sensor?
 
Both my Wife and I run Premium in our vehicle. Her's, a 96 Full Size Bronco, went from 11mpg city to 14mpg which more than offsetts the cost of the fuel. My XJ is getting 17 in town, 19 on the hiway on the stuff. I think that part of the benefit is the injector cleaner that is in premium.

I do know that after I snagged the XJ last May, it was getting 10mpg in town. Plugs, Wires and Cap took it to 12mpg. 99+ Intake and a Header (my manifold was cracked, what a surprise. One of the reasons it was so cheap...) plus a Magnaflow Cat and 2.5" cat back got me to 14mpg. Fixed the dragging caliper, 15 mpg. Off the Shelf cold air cleaner bumped me up to where I am now.

Every step has improved the performance and the mileage. Now, I can lift it and destroy all my gains...
 
No matter what cleaner their advertising this month premium or higher octane fuel is made for higher compression engines. If it was a cleaner in the fuel that helped your mileage why not run regular and use an additive. Your engine will run even better and save money at the same time.
 
The tips I've gathered seem to stack up like this
1. Change driving habits - lighten up on the skinny pedal
2. Tune up. Plugs, wires, cap & rotor, air filter, cleaning throttle body
3. Synthetics when you do your fluid changes
4. Cat back exhaust / 99 intake / cold air intake / performance fuel injectors / E-fan swap

The items at #4 have been consistently touted as 1 MPG apiece. I don't drive much so for me, they come in last. It would take at least a year for a 150 dollar add-on to pay for itself, unless the OEM needed replacing anyway. If you drive a lot, these mods should pay off quickly.
 
Both my Wife and I run Premium in our vehicle. Her's, a 96 Full Size Bronco, went from 11mpg city to 14mpg which more than offsetts the cost of the fuel. My XJ is getting 17 in town, 19 on the hiway on the stuff. I think that part of the benefit is the injector cleaner that is in premium.

I do know that after I snagged the XJ last May, it was getting 10mpg in town. Plugs, Wires and Cap took it to 12mpg. 99+ Intake and a Header (my manifold was cracked, what a surprise. One of the reasons it was so cheap...) plus a Magnaflow Cat and 2.5" cat back got me to 14mpg. Fixed the dragging caliper, 15 mpg. Off the Shelf cold air cleaner bumped me up to where I am now.

Every step has improved the performance and the mileage. Now, I can lift it and destroy all my gains...

Running premium in an engine that doesn't need the extra octane can actually have the reverse affect. You will get the best mileage from running the lowest octane without detonating. My totally stock 91 with 217K miles is pulling just a bit over 20 in commuter duty on 87 octane, and I get 23 on the highway with the cruise set at 75.

Also, as of 1995 ALL gasoline in the US regardless of octane must have agents that prevent deposits. All the crap about the higher octane stuff being better and having special cleaners is all marketing hype.
 
Yeah don't run the high octane. It is 100% waste unless you have built a higher compression engine or are running an aftermarket tune designed around higher octane fuel.

My dad still believes in putting in the "high test" (93 octane) gas every few fillups actually makes a difference. I tried to tell him that his car ('01 Lincoln LS) wants 89 octane and going from 87 to 93 every now and then is the worst thing he could do for mileage. Just run 89 all the time and the engine will not have to adapt back and forth!

Anyway it is a losing battle, he will never listen to me and others running 93 in a Jeep won't either! haha

FWIW my friend is a certified mechanic and he built a high compression 4.7L stroker motor and calculated it wants 89 octane and it ran great. 93 in a stock motor is a horrible waste of $$
 
My dad actually ran some numbers on his fuel economy and found that buying second-tier gas cost him less money per mile at one point. Never figured out if it was because he was driving it more sanely with the more expensive gas, or if it was running more efficiently on it, but whatever it was, it resulted in less money being spent so he went with it.

Only real way to test this would be on a closed course with all other variables (air pressure, humidity, temp, wind, etc) held constant, in a double blind test, or using an engine dyno.
 
No matter what cleaner their advertising this month premium or higher octane fuel is made for higher compression engines. If it was a cleaner in the fuel that helped your mileage why not run regular and use an additive. Your engine will run even better and save money at the same time.
Because lets say you fill your tank 15gal/$48.75@ 3.25/gal premium thats only $2 more than regular being its 46.50. and its about $4-8 for the additive so youre better off just buying premium..
 
Uh, you don't put a whole bottle of additive in with every fill-up.

Others have already said this but I will add that you don't necessarily have to buy premium grade to get the additives. Chevron has their techron in all grades. There is a Shell station locally that generally has the lowest pump prices in town and Shell advertises that their nitrogen whatever is in all grades.
 
Because lets say you fill your tank 15gal/$48.75@ 3.25/gal premium thats only $2 more than regular being its 46.50. and its about $4-8 for the additive so youre better off just buying premium..
I’ve never bought additive so I really don’t know what it costs. Basically I was saying run the fuel you engine was designed for.
 
Uh, you don't put a whole bottle of additive in with every fill-up.

Others have already said this but I will add that you don't necessarily have to buy premium grade to get the additives. Chevron has their techron in all grades. There is a Shell station locally that generally has the lowest pump prices in town and Shell advertises that their nitrogen whatever is in all grades.
Most bottle I've picked up said to use entire bottle with around 12gal fuel. But I'll go to my nearest parts store tomorrow and double check all their additives
I’ve never bought additive so I really don’t know what it costs. Basically I was saying run the fuel you engine was designed for.
Oh ok
 
Sorry, I didn't say that exactly right. I agree that when using the additive, you use the full bottle with a tank of gas. What I should have said was that you do not need to do this with every fill-up, so the cost of the additive is spread out over several tanks of gas.

When I consistently use a gas from a source that doesn't claim to include a cleaning additive (e.g. Raceway), every six months or so I run a bottle or two of Techron through the system. I don't have a clue as to whether or not this helps significantly in keeping a clean fuel system.
 
Keep your speed to 55-65, go easy on the hammer, and maintain the vehicle well with stock tires/gears and you should see 350-400 easily.
 
Keep your speed to 55-65, go easy on the hammer, and maintain the vehicle well with stock tires/gears and you should see 350-400 easily.

yup, i have done it with 30" and 3.55 gears in a manual and even going a little faster than that. google map checked on numerous trips. granted as soon as i get offroad all bets are off.

top gear did an awesome clip in season twelve i think about gas mileage. prius v newer v8 m3. it showed that the biggest thing for gas mileage really is driving style.

http://www.youtube.com/watch?v=dKTOyiKLARk

just curious but has it ever been suggested naxja get an eco tuning sticky/subforum. would be good for those of us who love our jeeps but hate spending $$$$ on gas.
 
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