Gas Mileage 5.7L automatic K1500, 4WD

What is the best possible gas mileage? I get about 12mpg city, 14 mpg highway.
Is there any modification that will truly pay for itself ?? headers? dual exhaust? change from TBI to Carburator?

Dropping the TBI definitely won't help...

1. none of the POWER MODS will help, only make it worse.
2. mpg improves after 70K miles, when engine breaks in.
3. here's things that DO work:
- HALO spark plugs, proven by many researches
- hight air flow filter. FILTER, not cold air intake
- belly pan to reduce drag
- full body aerodynamic modification
- replacing metal sheetwork with fiberglas or carbon, to reduce weight
- using low rolling resistance tires
- driving habits modification

http://peswiki.com/energy/Directory:Fuel_Efficiency

K & N filter, smog-legal headers into 3" to 4" to 5" single exhaust, Edelbrock TBI intake, $600 dyno tune.
Catro Syntec 10-30 oil. Run 39 lbs cold pressure in 255-70X15 BFG T/A's.

Now up to 14 city, 16 highway. With a 383 small block. and 60-70,000 miles on tires. Truck now has 430,000 miles.

I have found that an underdrive pulley,a hotter ignition coil and a k&n air filter to give me 17.73 mpg on hwy at 70mph. total cost (plus new serpintine belt)under 200. 94 z71 5.7l auto.trans tbi.i am very pleased

FMX guy,mind if I ask what brand of coil you used?

msd blaster coil. the one made for gm replacement $45.00 asp underdrive pulley $65.00 both from summit and of course k&n most any parts house around 50 bucks i spent like 2 hrs total putting all of this on and got immediate results the only draw back is that it does slow the accessories alt. a/c pwr. strng. at low rpms its kinda a pain, but at hwy speeds no prob. eventually i will get a high-end batt. a higher output alt. and elec. fan

Appreciate the response. I swapped for K&N a while back and considered undersized pulleys but I tow a camper and wasn't sure if that would be a good idea so have the originals. I think I will go with a hotter coil though, sounds like a good idea.

Has anyone seen better mileage from replacing Oxygen sensors??

Only if they are bad.

What year truck do you have?
What is the gear ratio?
Best help for gas mileage is a good AC delco tune up.
Also driving habits has a lot to do with it.

Has anyone seen better mileage from replacing Oxygen sensors??

since you have the 5.7L I'm guessing this is a 1990's vehicle..if the O2 has over 100,ooomi and is original..many have seen improvements in MPG and also with performance.with replacing...With the new style 5.3L vortecs the computer senses these very closely and if they are off you will quickly get a dtc telling you so...


if your mileage is around 16-17mpg this is normal for that engine/vehicle..

try cleaning the maf sensor with the MAF cleaner spray...spray the small sensing wires carefully...use a K&N filter...easy on the oiling though MAF gets oily, not good...using synthetic oil in the engine also helps mpg...

Only if they are bad.
What year truck do you have? What is the gear ratio? Best help for gas mileage is a good AC delco tune up. Also driving habits has a lot to do with it.

It's a 1/2 ton daily driver, 4x4(for winter driving), 1998 K1500 with 115,000miles, 5.7L runs great, automatic, all tune-up items completed, MAF cleaned, good driving habits, stock everything, stock tire size, almost always in 2WD....
3.73 gears,(that's why I expected a bit better mileage).

Don't believe the K&N marketing hype, I removed the K&N filter that was on when I bought it. With the 3.73 gears and driving for economy, this engine rarly even hits 3000 RPM. IF there is a benefit to the K&N filter, it is only noticible at high RPM's (when there's lot's of air flowing). In real-world driving, most trucks would never benefit from KN unless they are seriously hauling / towing, in which case a half-ton truck like this would be the wrong choice anyway....

So that's how I got to the point of looking at O2 sensors as the next "maybe", but the $100 for a pair of sensors would take a long time to earn back on gas mileage if it was only a small gain. Thanks.

It's a 1/2 ton daily driver, 4x4(for winter driving), 1998 K1500 with 115,000miles, 5.7L runs great, automatic, all tune-up items completed, MAF cleaned, good driving habits, stock everything, stock tire size, almost always in 2WD....
3.73 gears,(that's why I expected a bit better mileage).

Don't believe the K&N marketing hype, I removed the K&N filter that was on when I bought it. With the 3.73 gears and driving for economy, this engine rarly even hits 3000 RPM. IF there is a benefit to the K&N filter, it is only noticible at high RPM's (when there's lot's of air flowing). In real-world driving, most trucks would never benefit from KN unless they are seriously hauling / towing, in which case a half-ton truck like this would be the wrong choice anyway....

So that's how I got to the point of looking at O2 sensors as the next "maybe", but the $100 for a pair of sensors would take a long time to earn back on gas mileage if it was only a small gain. Thanks.


so whats the MPG ? what oil do you use ?

you forgot something that most dismiss with these K&N filters....they last a good 10years so you save money because thats ten paper filters you would have purchased..also the paper filters especially in dusty areas need very frequent replacing...this adds up..

as far as gas mileage goes no change except if you tow heavy loads ..then the extra air helps ..

earlier in the post i did forget to mention that i have 3.42 gearing and true dual exhaust(not cat back) in my 94 z71. also i had the front end aligned wow. i didnt think it was bad to begin with. but it helped on my gas mileage even more.stock size all-terrain tires. good maintanence,tires,etc. goes a long way.Also changing the driving habits can be a stumbling block.