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Discussion Starter #1
I have closely monitored my truck's MPG for the last 12 tank-fulls.

Does 10.5 (average) mpg sound right for my truck? K&N drop-in air filter, new plugs, dist cap, rotor, and synthetic motor oil?

No matter how light I drive, city or cruising on the highway, I always get 10-11 (if I am lucky) MPG .

I even took my tool box off (that was full of tools and gear) and added on a cab-high bed cap. I have used a can of Seafoam and a can of 3M Professional Series fuel system cleaner.

4.10 gears with LT285 (with proper PSI). Stock converter (perfect smog readings), 3" exhaust going into a 3" inlet Flowmaster 40 series with dual 2.5" outlets.

The truck starts, idles, and drives completely fine. There are not any fualt codes stores in the PCM. I was thinking of trying a new air intake kit, to help push some more air into the motor, since the drop-in K&N does not flow any real CFM.

Any ideas?
 

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switch out the gears they are what are killing your MPG or slow down to no faster then 55
 

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When I bought my truck with the 4.10 gears and 285s that you have on your truck now I got the same milage. The highest I ever got was 12 but normally got in the 10-11 range.
 

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Yup sound right! I monitored my fillups for my 94' for 5yrs! All in a spreadsheet. 9-11mpg is what I averaged. Changing the stock 3.54's out to 4:10's did no worse or better.
Changed the ignition (Jacobs, see tech page) That too didn't help with economy. Power yes, MPG NO.
I finally got decent fuel economy, took $35k to do it, but I average now around town 18-19mpg. Achieve 22 on long trips.
And my CTD is PAID OFF NOW!
:bigthumb:
 

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i get 8-9 around town, 12-high 13's on the highway.

im running 37' mt/rs, 4.10s, Superchips, headers, roller rockers, M1 w/turtle, 21# FMS injectors, 180deg thermostat, and a dual in Carsound cat to 3" pipe to a Gibson muffler then to split rears.

the around town is crappier then stock, but the highway is about the same as stock for some reason.
 

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your right on i have 3.55's and i have always got around 10-11.5
 

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thats what i get and flock 55, i drive 70 minimum on the highway i get more.


and if you want better mpg get a ricer with a 4 banger
 

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I would get 10-11 on the highway at 75.

Slow down to 55 and I could pull 15.

65 I would get 12.

Monitored my gas for 70k miles, and I only would see 1 mpg jumps every so often from stuff like the spintech muffler (not the magnaflow), and the new timing chain.
 

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you could try to go with a slightly larger tire to see if that helps :D: ; But seriously when I went from 305's to 315's I got better mileage on the freeway; the added tire size made my gear ratio higher dropping my RPMs. I'm also running a V-10 with 4.10 gears.

I recently saw a chart that somebody posted on this sight. I believe it had to do with gears, tire size, and RPM.
 

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try getting 6 mpg on the highway and in town on a good day :wall: I would have to say change your gears and you will get better mileage but not much more...nature of the beast :sorry:
 

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Discussion Starter #14
On 2005-11-25 23:09, weaktruk wrote:
All the above :withstupid: Point is, do you like your truck enough to keep it with that MPG? I know I do.

I definitely will not be getting rid of my truck soley because the gas mileage. I was just checking to see if the 10 MPG was low and something possibly may be 'faulty', since the truck is covered under the 7/70 powertrain warranty.

The truck has 48,000 miles on it now. I do really enjoy the truck, because it tows plenty, hauls anything I need to move/store/transport, and it can it a great hunting vehicle for this time of year.
 

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Discussion Starter #15
On 2005-11-26 09:37, Gabe7g wrote:
you could try to go with a slightly larger tire to see if that helps :D: ; But seriously when I went from 305's to 315's I got better mileage on the freeway; the added tire size made my gear ratio higher dropping my RPMs. I'm also running a V-10 with 4.10 gears.

Last year, when I had the LT315s on my truck, I was getting 8.5-9 MPG. I was just thinking that by changing to a LT285 tire, it would weight alot less and also have alot less rolling resistance; thus getting more than a 1 MPG increase over the LT315s!

I should have just kept the LT315s!!!.........those looked and performed great on my truck! Oh well.

When these LT285s wear out, I will be going with an LT295 sized tire. The LT315s fit the truck really good, and the LT285s look very small under the truck.
 

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it's the engine, gears, and tires. the 5.9 is gonna suck gas a lot more than a 5.2. like 4 mpg more or so. the 4.10's with 285's is gonna put you about 300 rpms over 3.55 gears.

plus, it might just be cuz we are in indiana and the roads here suck.
 

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On 2005-11-25 19:00, jprtroy wrote:
Yup sound right! I monitored my fillups for my 94' for 5yrs! All in a spreadsheet. 9-11mpg is what I averaged. Changing the stock 3.54's out to 4:10's did no worse or better.
Changed the ignition (Jacobs, see tech page) That too didn't help with economy. Power yes, MPG NO.
I finally got decent fuel economy, took $35k to do it, but I average now around town 18-19mpg. Achieve 22 on long trips.
And my CTD is PAID OFF NOW!
:bigthumb:

I was having the same problem with my '98, so I had to shell out $35k also and now I get 16-18 MPG city and 19-23 on the highway.
 

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If you can afford it, get you some wagon wheels with stock size tires to run when you are not wheeling. Should help out atleast 1-2 mpg.

When I swapped my Desert Duelers for the BFG Mud-Terrains my mileage took a nose dive.
The larger tires are simply more mass to get rolling, plus the mudder tread pattern (I am a$$uming that 'Wild Spirit Radial RVT' is a mud tire) catches a lot more air and produces more drag.
I don't think switching back to stock gears will affect it, you have an almost stock drive ratio with the larger tires.
My 4.11s actually helped my mileage (in town) over the 3.55s, highway stayed steady at 15-16.
Granted I am caseless, so I have less moving parts and am weigh less.

Did you notice much of a change when you swapped throttle bodies?
 

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I accually just got rid of my BFG 315's and got some Cooper 285's. I personally think it rides, performs, looks better than it did with the 315's. Gas Mileage meh. I also have 4.10's and the truck doesnt seach for gears like it did with the 315's. Another plus is that when I off road I dont hit the fenders or the arms like It did all the time with the bigger tires... Sorry got off topic. But yeah the Gas didnt change that much, if at all, but I wasnt looking for that since I have a 5.9 I knew it would suck it down.
 

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On 2005-11-27 15:53, LPD111 wrote:


Last year, when I had the LT315s on my truck, I was getting 8.5-9 MPG. I was just thinking that by changing to a LT285 tire, it would weight alot less and also have alot less rolling resistance; thus getting more than a 1 MPG increase over the LT315s!

I should have just kept the LT315s!!!.........those looked and performed great on my truck! Oh well.

When these LT285s wear out, I will be going with an LT295 sized tire. The LT315s fit the truck really good, and the LT285s look very small under the truck.

Yeah, that pretty much proves my point. also with the V-10 I did not notice a difference in power at all. I think it has to do with the trucks shift points and them matching the tire size, gearing. With your truck 305's should be about the perfect size for all your needs. By the way I got those shotgun parts; they fit perfect.
 
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