Gas Mileage Help

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evilunclegrimace

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I didn't notice a change in economy when I went from 3.73 to 4.10 or when I swapped my 4L60 for a 4L80. Or when I put the blower on. It seems to get what it gets.

The 4L60e has a lower first and second gear than the 4L80E. Third gear being equal and over drive being different with the 4l60E having a 0.7 vs the 4L80e's 0.75.

The 4l60e is going to move the vehicle quicker/easier than the 4L80e. The 4l60E is going to allow the engine rpm's to be lower all things being equal. The trade off is that the 4L80E is a stronger transmission and will keep the engine in its designed power band.
 

CapnDean

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Gonna be hard to beat 12MPG in a 4WD 1996 with a 5.7 and 4.10 gears. That said have you compared your actual speed to your indicated speed on the speedometer? If you have not, use your smart phone and check your actual speed on the highway and compare it .

Due to the size tires I have on my truck, my speedo says 60 mph, but my actual speed is around 65mph. Since I am 5 mph off in speed, I am also 5miles OFF, in my mileage count. for every 60 miles that the odometer says I have traveled, I have actually traveled 65.

When my odometer says that I have been 350 miles.... and I add 5 miles for every 60 that I have traveled....That's 30 miles.

My last fill up was 350 miles on the odometer and I took 30.2 gallons of gas. Thats 11.5 mpg. If I add the 29 extra miles that I actually traveled to the mix.... I gain a whopping 1MPG. LOL I know it aint a whole bunch... These trucks were built to work and not necessarily be easy on the gas.

That said: I'm getting the same 10 around town and 12 on the highway out of my dually with a 454.
 

1989GMCSIERRA

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Okay so i have a 96 k2500 all stock except its on its third motor (second with me one before i bought) and got some different wheels the previous owner put on but still has stock tire size and no lift but i struggle to get anything better than 12mpg and i need some recommendations on how to get better mpg so any input will be greatly appreciated!!

So what’s your gear ratio? If it’s 4:10 with what 265/75/16? You’re probably about as good as it gets. Heavy 4x4 truck with low gears...it’s a trade off. You can pull stumps out but the mpg is gonna suffer.

what I would do is take out any stuff you may have stored in the truck that’s not needed.

I had a 1989 Chevy crew cab dually 4x4 454 with a Turbo 400. 8/9 mpg was all I got. I would of killed to get 12 mpg back then.

Fuel filter is a easy service. I doubt it’s gonna do much for mpg. Check your plugs, wires, cap, rotor and Air filter.
Keep your tires inflated to correct psi.do t hammer the throttle everywhere you go. When slowing down look ahead and let off the gas. Then ease back into the throttle.
Get rid of any protruding appendages like big lightnbars or roof racks etc.

another option is to find a front and rear axle with highway gears or regear but that’s gonna cost and its a long time to recoup the miney.

ultimately a Gearvendors overdrive will get that mpg up. But the 35/4000 cost kills any savings. I have a gearvendors in a f350 with a 7.3. 4:10 gears. The mpg goes from 14 with. O Gearvendors use to 16 with Gearvendors use. But it has to be long distance flat roads. Otherwise the only advantage is being able to split a gear towing.
 

98chevy2500SS

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12 seems normal for a heavy 3/4 ton w/ 4.10s. My 97 half-ton w/ 3.73s and my 98 3/4 ton w/ 4.10s get about 11-12 mpg average. Both are also on stock 265/75r16 tires.
 

Supercharged111

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So what’s your gear ratio? If it’s 4:10 with what 265/75/16? You’re probably about as good as it gets. Heavy 4x4 truck with low gears...it’s a trade off. You can pull stumps out but the mpg is gonna suffer.

what I would do is take out any stuff you may have stored in the truck that’s not needed.

I had a 1989 Chevy crew cab dually 4x4 454 with a Turbo 400. 8/9 mpg was all I got. I would of killed to get 12 mpg back then.

Fuel filter is a easy service. I doubt it’s gonna do much for mpg. Check your plugs, wires, cap, rotor and Air filter.
Keep your tires inflated to correct psi.do t hammer the throttle everywhere you go. When slowing down look ahead and let off the gas. Then ease back into the throttle.
Get rid of any protruding appendages like big lightnbars or roof racks etc.

another option is to find a front and rear axle with highway gears or regear but that’s gonna cost and its a long time to recoup the miney.

ultimately a Gearvendors overdrive will get that mpg up. But the 35/4000 cost kills any savings. I have a gearvendors in a f350 with a 7.3. 4:10 gears. The mpg goes from 14 with. O Gearvendors use to 16 with Gearvendors use. But it has to be long distance flat roads. Otherwise the only advantage is being able to split a gear towing.

Fuel pressure is crucial on the Vortec motors for the poppet injectors to fire correctly. They react worse than a TBI with low fuel pressure in some ways.
 

L31MaxExpress

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The 350 in my Express van always got 11-12 mpg city and 17-18 mpg on the open road running 70-80 mph. Stock cam, hotter cam, stock heads, Etec heads, stock spider, MFI spider, or marine intake. 4L60E or 4L80E. 3.42s or 3.73. When I swapped the van to full 1 ton running gear, suspension, brakes and put a 5.13 geared 10.5" 14-bolt under it I lost 1 mpg highway and increased my city mileage by 1-2 mpg. Driven conservatively the ~500 HP 383 is netting the same mileage as the 350 in the city and the 1 mpg highway has reappeared. I do run at 16.5:1 air/fuel ratio on the highway in lean cruise and have since the 0411 went in. I think the 383 gets better mileage than the 350 because it spends more time in lean cruise because it makes more torque. 11:1 compression probably also helps with the efficiency.
 

1989GMCSIERRA

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Fuel pressure is crucial on the Vortec motors for the poppet injectors to fire correctly. They react worse than a TBI with low fuel pressure in some ways.


Yeah unfortunately I know. I had a GMC that had a bad fuel pump. It was reading 57 psi at the rail. Manual said it needs 60 to function properly. You would think 3 psi wasn’t a big deal.
 

evilunclegrimace

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Fuel pressure is crucial on the Vortec motors for the poppet injectors to fire correctly. They react worse than a TBI with low fuel pressure in some ways.

I can attest to this, I ran my '98 suburban from my house to Knoxville TN and back at Thanksgiving (1200 miles) and pulled 16.2 MPG. The fuel pump was getting louder and louder and decided to change it before it left me stranded. The fuel pressure was 58-60 psi on initial prime and it would bleed to 54 psi in less than 5 minutes. I also had an intermittent crank but no start with no codes.

Once I got the pump changed the fuel pressure jumped to 60-62 on initial prime and would bleed to 57 psi after approximately 10 minutes. the intermittent no start disappeared and the fuel mileage went up to 18 MPG
 
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