Better gas mileage and performance.

NCchris said:

Sorry, in my sig, 5.7, 700 R4

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That’s damn good mileage. I was wondering if it was a 5 speed.

1989GMCSIERRA said:

Run stock size tires, drive normally and accelerate slowly. Take off crap in your car that’s not needed. I.E tire chains in summer. Tow chains for off road when yiure 98% on street.
If you have crap hanging off the truck off road lights winches roll bars and off road lights remove all that clean up the aerodynamics. If you removed the front airdam put it back on.
Keep tires aired up And make sure the alignment is good. Make sure brakes are adjusted right and not dragging.

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Accelerating slow has never saved any fuel for me. In fact it is just the opposite. Give the pedal a good 1/3-1/2 throttle shove and keep it open until you are up to cruising speed. The engine is most efficient accelerating a vehicle near its peak torque rpm. I am not saying stand on the go pedal, but give it enough throttle to couple the torque converter well, get it through the lower gears and into overdrive quickly and get it into lockup as soon as possible. You will actually burn more fuel starting off slowly by staying in the lower gears longer while the torque converter slips away wasting fuel.

Lucky lucky!!!! I get 13mpg on rural roads, and I have no idea on the hwy.

Just did a record today for 15.99 mpg just shy of 16 mpg mostly highway. Kept it at 60 mph everyone passing me was pretty upset but I'm usually in the slow lane anyways. I wonder if I change octane or go to 55 mph will I see improvement. And this is with big 26" wheels which equals out to 33" tires. Im pretty confident I can squeeze out more with the stock 16's. We should start a mpg weekly thread that be cool.

2drXmobb said:

Just did a record today for 15.99 mpg just shy of 16 mpg mostly highway. Kept it at 60 mph everyone passing me was pretty upset but I'm usually in the slow lane anyways. I wonder if I change octane or go to 55 mph will I see improvement. And this is with big 26" wheels which equals out to 33" tires. Im pretty confident I can squeeze out more with the stock 16's. We should start a mpg weekly thread that be cool.

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smaller wheels or regear

Caman96 said:

Sitting in a Prius 5’ behind a tractor trailer’s just not my thing.

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Your right it's really dangerous but the tractors creates less drag when your following makes our brick vehicles slightly more aero and efficient. I drive a tractor trailer everyday so I'm used to it. Everyone says I drive like a grandpa.

2drXmobb said:

Just did a record today for 15.99 mpg just shy of 16 mpg mostly highway. Kept it at 60 mph everyone passing me was pretty upset but I'm usually in the slow lane anyways. I wonder if I change octane or go to 55 mph will I see improvement. And this is with big 26" wheels which equals out to 33" tires. Im pretty confident I can squeeze out more with the stock 16's. We should start a mpg weekly thread that be cool.

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tayto said:

smaller wheels or regear

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My 99 Tahoe with a cammed L30 305, 4L60E, and 3.42s rolling on 32" tall P305/50R20s consistently managed 23 mpg highway rolling 75 mph. Cammed 8.1/4L80E dropped that to 19 mpg. The Express van has gotten over 21 on 93 octane pump gas and gets 17 on E85 on the highway. 383/4L85E and 3.73s with 30.5" tall P245/75R16s. I run the speed limit and do not roll much slower than 65 ever (lower posted limits) and usually 75-85.

L31MaxExpress said:

My 99 Tahoe with a cammed L30 305, 4L60E, and 3.42s rolling on 32" tall P305/50R20s consistently managed 23 mpg highway rolling 75 mph. Cammed 8.1/4L80E dropped that to 19 mpg. The Express van has gotten over 21 on 93 octane pump gas and gets 17 on E85 on the highway. 383/4L85E and 3.73s with 30.5" tall P245/75R16s. I run the speed limit and do not roll much slower than 65 ever (lower posted limits) and usually 75-85.

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That's impressive and amazing good job

2drXmobb said:

That's impressive and amazing good job

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Tuning helps alot on these engines. GM neutered them tuning them for 87 octane. 87 is a poor excuse for a fuel. The vortec heads make the most power around 30-33* BTDC timing advance and the stock GM timing map does not advance the timing more than about 23-25* BTDC at wide open throttle. The 195F thermostat operating temperature also drastically kills off timing. A 170F thermostat with a cooling system capable of keeping the engine under 180F is worth a bit of power and MPG as well. Keeping it cool helps you have a safety margin from detonation with the timing cranked up. Running cool on 91+ octane these engines like to run the MBT timing advance that GM already provided in the MBT timing table with big gains in torque and fuel efficiency.

my truck has 3.42s and 30" tire. OD is basically useless unless on flat ground or going down hill. I live in mountainous terrain, I would think that takes a big bite out of mileage. I had a 2bbl 305 w/ 2004R in an early 60s impala about 15 years ago. I would get 23-24 mpg, but this was in the prairies where roads are flat. i also knew nothing about carb or ignition tuning.

@L31MaxExpress I should get your help with my timing map sometime. I haven't had time to mess with it but it is a neutered for sure.