Trying to get better fuel economy in my '96...

[cam.man67]

While my Dart has been my daily for years, I find that I'm using my GMC more and more. Darn it! It just drives so good!

Problem is, I'm struggling with fuel economy in this truck. For reference, my '69 and '79 C10s averaged 9 and 10mpgs respectively...without efi, OD, or any sort of good aerodynamics. My GMC gets 11. I don't use the a/c hardly ever (unless driving my wife), I rarely haul (and even when moving 11000lb hay wagons, I got 10mpg), I mostly drive on the highway and am not aggressive at all on the throttle. The tires are aired up to 40psi, the truck runs great, and yet it is positively sucking down fuel. What can I do to improve this?

Since I've owned it (last September), it's gotten a TPS, plugs, wires, cap and rotor, new brakes, and a R134 top off. I'm really shooting for about 15mpg around town...is that unrealistic???

[speedygonzales]

I've owned mine since new December 1998. Obviously the way you see it now, it's not the best for mileage. I gave up trying to get better fuel eco from a CSFI years ago. Other than a good state of tune. You can't do much. Not talking about letting leaks and problems go. Obviously those need attention.

http://ecomodder.com/forum/EM-hyperm...ecodriving.php

BTW not sure if you know that the front O2s and the coil are considered tune up items. They can help with mileage obviously.

Changing tranny, transfer case and rear end lube can help slightly.

[72freak]

My 99 Z71 Tahoe hovers between 12-16. I saw 17 once on a highway trip.Changing tire size can also hellp a little.

Driving V-8's and concerning your self with fuel economy is really a wasted effort. These vehicles are not made for fuel economy.In my opinion anything that came from the factory that gets under 20 MPG is NOT a vehicle to worry about fuel economy. If you need fuel economy buy a vehicle made for such. I have a Honda Accord, A Subaru Forester and a ZTW Focus wagon and those are econo boxes. I get the biggest kick out of folks that ask someone in a hotrod or V8 truck..."what kind of gas mileage you get"...

[95 S_Trucker]

15 around town is out of line.

When these were new(1/2 ton, 4wd, 5.7), they were EPA rated at 12(city) and 16(highway at 55 mph) and those numbers are generous.


Go buy a 1000 dollar beater car, it will get good mileage and pay itself off.

I had a 94 olds achieva that got 26 mpg. It paid itself off in 7 months.


A pick up is used to haul and tow. Its not meant to get good mileage.


Please let us know when you tow 11,000 pound hay wagons. I don't want to be anywhere near you. You need a 1 ton+ truck or a tractor. That's too much weight to tow on a half ton, especially on a trailer without brakes.

[Tom]

Originally Posted by 95 S_Trucker

15 around town is out of line.

When these were new(1/2 ton, 4wd, 5.7), they were EPA rated at 12(city) and 16(highway at 55 mph) and those numbers are generous.
s.

So your saying 4wd removes 4mpg city and 5mpg freeway from the 2wd rating? Because I still have my window sticker for my 1/2ton 2wd extended cab 5.7L/auto and I'm rated 16/21.

OP- 15mpg around town might be at the high end, but 15mpg with you driving mostly freeway like you stated certainly is not.

When I bought my 98 at 75,000 miles, it would pull 22mpg on the freeway. It still runs great, and I've changed plugs, wires, cap+rotor but I've never done the coil, 02's, or installed the new style fuel injection setup. All that along with 100,000 more miles means I'm getting 18-19mpg freeway now. I'm assuming if I do the rest of the maintainence I'll get some MPG's back.

[cam.man67]

Thanks for the tune up comments...I wasn't aware that the o2 sensor and coil could affect that. Going another track, are any of the handheld programmers of any use organizing for economy?

[68C15]

my 99 Tahoe with 3.42 gears, 18 HWY, 16 if pulling my boat. In town I have no idea

[HeavyChevy81]

My 97 Reg SWB 4x4, Vortec 350 gets 20-21 on the highway to work, but falls to 14-15 around town. Ive done a lot of experimenting on it though. 3.42 rear gears, factory sized tires 265/75r-16.
Mods include:
ECM conversion to 0411. More resolution in Tuning
I use HP Tuners software to make my tweaks
New front O2's every 50k miles (currently 182000)
Cap, rotor, plugs and wires about every 25k

After LOTS of experimenting, and exhausting all kinds of theories in the fuel map, timing curves, TQ mgmt, etc. the biggest secret to better MPG's is...
tuning the Transmission. yep, I have made more forward progress with trans pressures, shift points and especially tuning the TCC timing.

I have played with the O2's rich/lean curve.
I have played with timing all over the place (keep the Active timing control Active)
I did see some improvement when calibrating my MAF.
But, again, my biggest improvement other that Right foot modulation, has come from transmission and Torque Converter Clutch application tuning.

Just my opinion.

[pwdcougar]

Originally Posted by speedygonzales

BTW not sure if you know that the front O2s and the coil are considered tune up items. They can help with mileage obviously.

What brand O2 sensors do you recommend Speedy?

Paul

[speedygonzales]

Standard motor products makes most OEM sensors. I get them from Summit.

https://www.summitracing.com/parts/smp-sg454

I had the back ones programmed at the same time I had the EGR programmed out.

After I get concrete in the garage and finish my bathroom project, I'm gonna do my ramjet 383 project. New management system from FAST the whole she-bang. LOL

[pwdcougar]

Originally Posted by speedygonzales

Standard motor products makes most OEM sensors. I get them from Summit.

https://www.summitracing.com/parts/smp-sg454

I had the back ones programmed at the same time I had the EGR programmed out.

After I get concrete in the garage and finish my bathroom project, I'm gonna do my ramjet 383 project. New management system from FAST the whole she-bang. LOL

Thanks Speedy. Does this one on ebay look like the same one? Says Standard brand and the correct number.

http://www.ebay.com/itm/NEW-STANDARD...1V0jn7&vxp=mtr

Paul

[speedygonzales]

Id say it's the same one

[Palf70Step]

My ole 96 2wd GMC extended cab average 14 around town and 18-21 on highway, AC always on. If you are running all highway, close the darn windows and run the AC, it actually improves the MPG. Another thing to remember is the fuel. In 96 there was no ethanol. That 10% ethanol will drop your MPG 10% or more which is around 2MPG highway.

As was mentioned, if you want MPG, driving a V8 truck is not the way to get it. To get the comfort, and convenience of my trucks, I deal with the MPG. If I wanted MPG, I'd be driving the CRV and look like a yuppie nerd... (of wait I am a nerd)

[OutlawDrifter]

Originally Posted by Palf70Step

I'd be driving the CRV and look like a yuppie nerd... (of wait I am a nerd)

Haha, Bill, you crack me up!


All of the above is good advice, don't drive a pickup for fuel economy. Keep it tuned up and enjoy the ride.

[Tom]

Nobody drives a truck for economy yet I fail to see how that matters with trying to get the best the vehicle is capable of? Its a worthy goal IMO.

[OutlawDrifter]

Originally Posted by Tom

Nobody drives a truck for economy yet I fail to see how that matters with trying to get the best the vehicle is capable of? Its a worthy goal IMO.

I don't think anyone is going to argue with that.

I keep track of every gallon of gas mine uses, it's also a great way to find out when something is due for a look over.

The point that is being stressed is don't go looking for huge increases that don't exist. In reality, spending money on "cold air intakes" and garbage like that, that may or may not increase you fuel economy 1-2 mpg, takes a lot time and gallons of gas to ever show value. 1 mpg more on 20 gallons is 20 miles(15mpg compared to 16mpg). How long does it take to recoup $300 at that rate? I'm all for keeping them tuned up and spending money on needed parts, but I have a 425rwhp Camaro for spending money foolishly.

[Palf70Step]

BTW, I did have an air-aide filter (K&N, but cheaper) & Flowmaster 50 Mufflers with true dual exhaust thru factory Cats. They probably helped economy, but not $ value wise. I did both just because I like the sound when I stomped it

[83GMCK2500]

If you haven't done it yet, ditch the CSFI poppet style injectors and put one of the MPFI conversions in. I've done 3 of them now between 5.7s and 4.3s, better economy/power/throttle response out of all of them. There may be a write-up on this forum that I'm not aware of, but here is one: http://www.fuelinjector.citymaker.co...onversion.html
& another article: http://www.fourwheeler.com/how-to/10...e-fueling-fix/

What did you use for tune-up parts, brands/etc?

[67swb72klb]

Originally Posted by 68C15

my 99 Tahoe with 3.42 gears, 18 HWY, 16 if pulling my boat. In town I have no idea

I have a 99 Sub 2wd that I bought because I couldn't find a RCSWB and I am getting about the same mileage 3.42 gears are the difference IMO