S-10 w/ 4.3L Bad Fuel Milage

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Ok, I have noticed other people talking about their vehicles getting poor fuel milage. I have a 97 S-10 with a 4.3 Liter V6, 4 speed auto and its 2wd
with a 3.08 Rear Diff Ratio. I have an 18.5 gal fuel tank. I get approx 250-300 miles on one tank of gas. I have P235 75R-15 tires on it. When i fill the truck up, the 1st quarter of tank of gas goes by damn quick. from 3/4 - 1/2 tank, it goes a little slower. Putting 235's on from 205's, does that make the truck sit a little higher? I know its a wider tire, but it looks like it sits higher too. Could this possibly have something to do with this poor fuel milage? I talk to other owners and they say they get close to 400 miles on a tank. I dont live in the city, I live inthe country, so any drive is atleast 15-20 mins one way or more. Engine runs fun, and truck has gotten shitty fuel milage for the last 4 years. Even after a tune up, I havent noticed fuel milage go up. i am trying to figure out why. Any comments welcome. thanks
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I have an 88 S-10 with a 4.3 and get 15-16MPG in town, and if I am lucky going down hill with a tail wind on the highway will get 17.5MPG.
It's 4x4, X-cab, has a topper, and 200lbs in the box. New motor (25K) a couple of years ago.
So I don't know if you are getting all that bad of milage.
The gas gauge (Chevy) is notoriously inaccurate. The trick is to learn how yours operates, and not worry specifically about exact accuracy. I used to have a car that would run 2 needle widths below red line empty before it was time to fill.
Tires do impact your fuel milage but I don't have the specifics for how much your application has changed things.
The only other things is make sure your O2 sensor(s) are working well.
Big Chris
KMU wrote:

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Have the same engine, but I think it depends on where you live...In Calif we have been blessed with "oxygenated gas", ie: crappy gas blended to burn better but with much less power and therefore worse milege
It gits only about 14 around town and as much as 19-20 on freeways, BUT when using Nevada gas, 26 on the freeways.
I've calibrated the gas guage by filling up at each 1/8 mark and writing down the gallons used Once it gits down to a 1/4 tank, I start lookin for a pump
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I live in indiana and own a 99 jimmy with the 4.3 and it only gets 15 on the highway and about 10 in the city if I am lucky

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I'll post a picture of the truck later today.

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"KMU" wrote:

When
so
When you went from 205 to 235 you went from a effective gear ratio of 3.08 (which is really to tall for OD) to about 2.73 which is even worse. Some will tell you the taller the better for MPG but you have reached the point that the engine is laboring with tall tires and extra drag. You can go back to 205s or gear up to a 3.42 to get back to were you were before in overall ratio or evena 3.73 if you want a bit more pep too. The MPG with your setup should be about the same with a 3.42 or 3.73 because of OD though a 3.73 might do a tad better beacause it will give you a OD ratio of about 2.6 or a little taller than you have in drive now with current setup. Try driving on highway without OD now and I will bet MPG will go up.
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Sounds about correct for the 4.3. It is not an economy engine. The 235s (depending on brand) will be from 1/2"-1" taller than the 205s. The 18.5 gallon tank means you can actually use about 18.2 gallons until the pump draws air. If you want to find out what you are actually getting fill the tank up, write the mileage down, drive it until you need to fill up again. Write that mileage down. Fill to the same level as before. Subtract the starting mileage from the current mileage. Take that number and divide the gallons by it. Do this two or three times and average out the numbers you get. That will give you a good number to start with. As for the gas gauge, they are only useful to tell you that your getting low on gas. If you want to see how bad yours is off, watch it while you fill up. see how many gallons it takes from mark to mark.
Steve W.
-
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I have a 92 S10 with 320,000 miles on it. I average 15.5-17 mpg on the highway. I used to get 20mpg easily but it's getting too tired now.
LS

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I agree, I was shocked to see the mileage some people are getting. I'm not sure what the gearing is on mine. It is a pooch at lower speeds so it must be geared for highway.
I pulled a 3000lb pop-up with it and usually get 13mpg which I thought was good with that many miles on it.
LS

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KMU wrote:

you will have to remember That your Speedometer/odometer is Wrong with the bigger tires. You are Traveling Farther than the odometer says. you need to get the Computer Chip Reprogramed for the TIRE size.. The rule for my 89 was that u could go up 2 sizes and NOT REPROGRAM the computer CHIP! The larger tires also Messes up The ANTI LOCK BRAKE SYSTEM !
I have a 89 s-10 4.3 $x$ automatic 205,000 miles and it Still gets 26 miles to a gallon and It Has the P235 75r 15 tires . it had 195 x15 tires on it when I bought it NEW
. When i

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I have a hypertech power programmer 3, I used that to correct the speedo and odometer. Doesnt do a shit for more hp or speed, just changes shift points and raises top speed cut out. Damn check engine light has came back on tonight. I need to get it in and have it checked. Its running rich and I'm getting like 9 mpg at the moment.

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By the way, would everyone take a look at them pics I posted? Tell me what ya think of her, I would like to sell it and get a newer S-10 like 03 that is 4x4, but not ZR2. Just the standard 4x4.

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You said the first 1/4 tank goes fast, have you looked at your gas tank to check for leaks?
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no leaks.

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I tried using 3rd gear around my house, and the fuel milage went down a little bit.

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"KMU" wrote:

You cannot really tell from a day or two, you have to get the average for several days under differing conditions too.
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KMU wrote:

<snip>
    Doesn't look to hatefull. Personially Im looking for a ZR2 Blazer or Extended Cab project (basket cases perfered). I can say this your new style S-10 looks better at 350K then the 179K 89 2WD body on my 89 4x4 frame does. The frame is about ready for it's third body shell, with over 400K on the 4.3 & TH700R4. I have 3.42 Gears, and 235/75/15's on all 4 corners.
    When I first put it back on the road I got about 17 MPG mixed driving. Now im down to about 7 to 8 MPG. A Torque Converter clutch & switch problems, as well as a whole list of abused S-truck issues killed my milage. Ill get to fixing the issues when I get the new cab on my 91 S-15 Extended Cab pick up. (another roll over project).
    As someone else said 3.08 gears are probably killing you. 3.23 or 3.42 would do better under 70MPH. 1,500 to 2000 is a good cruise speed with the torque converter locked.
    As for the topic of Astro Vans, a 4WD S-truck weights less, yet has less aerodynamics, and more rolling resistance. In town 4.3 Astro's and 4.3 S-10's get about the same milage.
Charles
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Numerous undercoatings, and the paint being wheeled out atleast 7 times a year. hehe, I'm alittle anal, the least to say.

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Sorry I said it had 350k, I wasnt to sure of the exact milage. when I took the pic of my cluster, it had 396k miles, it should be rolling over to about 400k by friday, I have to drive to detroit every day this week. I hate traffic, thank god for eway

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On Wed, 29 Jun 2005 10:59:46 GMT, Charles Bendig

Charles, too bad you're in Ohio, I have a ZR2 Pickup I may be selling in the next few months. Depends on what you want to spend though. It's in good shape but has 2 small problems...
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