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only 14mpg help!

 
  #1  
Old 11-10-2005, 03:41 PM
71 Muddbugg
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only 14mpg help!

I just drove my '95 bronco on a 490mile trip, all highway, and only got 14 mpg. It has a 302 auto and runs like a top. It has dual exhaust and 31" rubber. I drove it nice because I wanted to see what I could get for mileage so it never went over 60mph.
Shouldn't a 302 get better mileage than that? 35 gallons is alot of fuel for an easy drive.
I would like to know what can be done to this motor to get a couple miles per gallon out of it. Normally I drive around 70 on the highway but don't normally figure out the mileage, I'm more concerned about getting there!
The odometer reads 378,000km (or 236000 miles) I do not know if the motor is original. It does have a loud lifter but uses no oil. Factory style air filter, regular octane fuel, 45,000km on plugs and wires.
I know a few people who run 302s and claim closer to 20mpg on highway.
What do you think????
 
  #2  
Old 11-10-2005, 04:08 PM
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Don't know who those people are claiming to get 20mpg from a 302 unless they are running it in a Mustang! The absolute BEST mileage I ever recorded from either of my 302-powered Broncos was about 18-19 and that was right after a complete tune up including the replacement of the fuel filter and the addition of a K&N drop-in air filter along with my Bassani exhaust sytem installed. The trip was a straight run from Kansas City to Salina. I-70 about as flat and unchanging as you can get. I'm not saying its impossible, I'm just saying that given the miles on the truck and presumably the engine as well, you got pretty good mileage from it. Even if it doesn't consume any oil, the compression on an engine with that many miles is still not what it was new or at even half that many miles on it.

You mentioned dual exhaust... true dual? It can't be OEM if it is. Does it have an "X" or "H" pipe connecting the exhaust from each bank of cylinders? This could easily be part of the problem.
 
  #3  
Old 11-10-2005, 05:42 PM
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no matter what i do to my bronco ('91 302, E4OD) the best i get is almost 15mpg, like 14.8ish. all mixed driving, i live in upstate NY and commute to college and work. so its not great on gas in this terrain. i have a K&N air filter, and a flowmaster cat back dual exhaust, and i replaced almost all the sensors, EGR valve.

i think if your getting 14, be happy with that, its a depressing number, but consider the fact that we are driving a 5000lb brick down the road, thats really not that bad
 
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Old 11-10-2005, 07:02 PM
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be happy man, not to bad really. Im getting 12 in my 300 six. Larger tires and gears will do that, but i'd be happy with 14.
 
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Old 11-10-2005, 07:58 PM
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A fuel filter and k&n air filter is something I haven't done yet. The exhaust is dual right from the manifolds. Bottles, no cats, no H pipe. I heard a cross over pipe does help a bit too. Maybe try that. Sounds like the old girl is still in the ball park....

Thanks Adam
 
  #6  
Old 11-11-2005, 12:19 AM
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If you have duals with no crossover in the form of an H or X pipe, where the heck is your O2 sensor mounted? Because if its mounted in only ONE pipe, its only getting HALF the reading it should be getting! As a result, the computer "thinks" the engine is running VERY lean and is dumping a lot more fuel down the injectors than necessary. thats the root of any problem right there.
 
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Old 11-11-2005, 10:14 AM
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i did get 16mpg/hwy in my bronco with a 5.8/AOD but now that im running 35's on stock gears im down to 12 on the hwy. i dont even use 4th gear now.
 
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Old 11-11-2005, 07:07 PM
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repeating what the other guys said, i get only about 16 mpg on the highway and my 92 Bronco is well taken care of. I go about 68 cruising and i feel like an old man driving when these sports cars and those little death trap cars wizz past me. I think the only way you can truely get more mpg is to remove the rear bench seat, remove as much weight as you can bear, and keep the tire pressure where it ought to be according to your tire size. I heard that you can replace that metal hood,with a aftermaket one,which would be fiberglass but how much would that help?
 
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Old 11-13-2005, 05:22 PM
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Mabe think about replacing rear end gears to get better gas mileage. Although playing with tire size can be a pretty easy fix too, and be SURE your tires are properly inflated, a lot of gas mileage can be lost through underinflated tires. Regarding the K&N filter and fuel filter, if yo've got dirty gas, by all means replace your fuel filter, bu otherwise I seriously doubt either will give you any more gas mileage.
 
  #10  
Old 11-13-2005, 09:55 PM
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Originally Posted by greystreak92
If you have duals with no crossover in the form of an H or X pipe, where the heck is your O2 sensor mounted? Because if its mounted in only ONE pipe, its only getting HALF the reading it should be getting! As a result, the computer "thinks" the engine is running VERY lean and is dumping a lot more fuel down the injectors than necessary. thats the root of any problem right there.
This is the second time I've seen you post that. I am calling you out.

Having an O2 sensor in the passenger side will not cause a very lean condition. The O2 sensor measures the percentage of the unburnt oxygen in the exhaust and unburnt gas. It does not measure volume of oxygen or gas, it just compares the one to the other.

If your theory was correct, his motor would go into limp mode, and would get a lot worse mileage than 14mpg.

I will agree, however, it could give an erroneous reading if one bank is running leaner or richer than the other. I also think you should have it in a crossover pipe for a better reading of the whole motor.

I just wanted to point this out, I've seen you post a lot of great information, but I cringe when I see this.
 

Last edited by bremen242; 11-13-2005 at 09:58 PM.
  #11  
Old 11-14-2005, 09:48 AM
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Greystreak is correct on the O2 sensor placement. When they did my duals they put one before the cat and the second in the X-pipe. My muffler guy said I could use the foolers but he thinks they run better with them. I am getting 17-19 mpg in town and 18-20 mpg on the highway. New air filter, new fuel filter and fuel system flushed before adding the duals. I do depend a lot on my "right foot" regulator and cruise control for my numbers.
 
  #12  
Old 11-14-2005, 12:01 PM
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17-19 mpg town? dam I could only dream of those numbers even with xtreme right foot regulator and cruise.
 
  #13  
Old 11-14-2005, 12:12 PM
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Originally Posted by greystreak92

The trip was a straight run from Kansas City to Salina. I-70 about as flat and unchanging as you can get.
Are you talking about the trip from Kansas City, MO to Salina, KS? I don't think you can really characterize that as "flat". Sounds like decent mileage for a trip through the Flint Hills.


Now Salina west is a different story.
 
  #14  
Old 11-14-2005, 02:31 PM
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I would feel lucky to get 14+ anywhere on my 95 302 5 speed...Maybe if I coast a lot. Then again most of my trips involve going up- Denver west.
 
  #15  
Old 11-14-2005, 03:05 PM
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14 is about right, but if I'm getting 16mpg in a clubwagon (1.2 ton version) with stuck front brakes I think you guys should be able to as well. Here is where I would start. Good tune up. New plugs, wires, everything, buy the motorcraft plugs, and dealer wires, cap and rotor. A lot of the aftermarekt stuff is inferior. Get an H or X pipe installed, and put the o2 sensor in said X or H pipe so it can read both banks not just one. Also have the injectors cleaned. It's possible that one is stuck open a little allowing more fuel than needed to flow... BTW my 302 has 306,000 miles on it...
 

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