Gas mileage improvement options ?

Now that the weather is warming up I am looking to change the exterior appearance of my vehicle plus also look to some performance mods(while power is nice I am mostly looking to improve gas mileage). I have a 99 4dr w/5.7 liter engine that has close to 80,000 miles on it.

I was looking to upgrade to a dual exhaust( I thought that the exhaust probably merged under the truck to a single pipe but while doing my oil change the other night I noticed that the exhaust is dual until it gets to the muffler.

Will I get much of a performance increase by changing out the muffler and going to 2 mufflers and dual tips? My financial adviser like most women is does not want a lot of noise so it needs to also improve gas milage.

I just changed the pcv valve, about to change my sparkplugs in a few days, and looking to get nice looking intake w/reusable filter to allow the truck to breathe easier. Since the truck has not hit 100,000 miles yet I was not planning on doing my wires yet (should I ?).

What else should I look at to improve gas mileage ?

buy a toyota :clapping:

sorry not meaning to be rude at all, but when you have a land yacht the last thing I look for is mileage, I always say that anything over 15 mpg is a bonus. my 98 hoe gets between 18 and 20. performance ad ons usually mean more gas, a good tune op is always good, are you still using mineral oil? if you are i would switch to a synthetic it should help out with milage a tad but will also help with cooling as well in the warmer months. makes for easy starts in the winter too.

i bought my hoe for towing and family, i cant stand pulling a hill at 40 mph, good luck and have fun

MPG TIPS

best thing i have found for mpg is allowing the engine to breath more efficiently. this is best done by the $250 K&N filter and intake kit then a true dual exhaust system using a flowmaster muffler and removing the catalytic converter. u don't want straight pipes b/c backpressure is key for the engine to function at its full potential. many other bran mufflers will work just as good. i just like the sound of the flowmaster 40 series. it sounds old school and doesn't have that redneck pop. u can get delta flow 70 series if u dont wanna hear it. also, aftermarket makes performance catalytic converter if u don't wanna break the law or need to pass vehicle inspection. something i don't have to worry about in SC after u make the engine breath better then u can help the computer interperet the airflow more efficiently by purchasing a Granatelli Mass Air Flow Sensor (MAF sensor). vortec vehicles have them, but the granatelli is way more sensitive and less restrictive (costs $400 tho!) there are also settings u can use to get more out of your ECM (computer, called an Electronic Control Module) this can be tuned by a Superchips or Hypertech programmer plugged into the diagnostic port, or u can buy a "piggy back" chip that splices into the ecm wiring harness and is not adjustable. these are available on ebay as well for about $30 and are ez to install if you are not color blind. a throttle body spacer can help the engine breath better too. a more powerful ignition, bigger spark plugs, plug wires, and distributor will help ensure all the fuel that goes into the engine is burned up and used to its full potential. this is a basic starting list of the things most everyone should do to their vehicle if they want to get the most out of the stock engine. to do all this it would probably cost about $1800 plus labor, so u can buy a whole lot of gas for that money... i would say get the k&n and a programmer only unless your definitely gonna keep the vehicle for a LONG time. those 2 will be most noticeable by your right foot!

Don't forget about replacing the O2 sensors on a regular basis.

Hardwarz

jwpotts0413 said:

i would say get the k&n and a programmer only unless your definitely gonna keep the vehicle for a LONG time. those 2 will be most noticeable by your right foot!

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:yesnod: Agreed -- intake and programmer (plus synthetic oil and 93 octane fuel) have gotten me a nearly 35% improvement over stock mileage. Jury's out on the throttle body spacer tho -- seems lots of people think they're useless on a fuel injected vehicle, which is why I won't get one. The Denali already has a 3.5" exhaust system (can't see improving on that with my ride until someone comes out with a dual system for the 6.2L). Good luck!

Don't forget the fuel filter. Intake and exhaust will make the most noticeable bang for the buck difference.

you could always make sure you're always going downhill.

:thumbsup:

or, like everyone already said, intake, exhaust, sensors, etc.

the tb spacer i used was a Helix power tower. it prolly gave me 1-2 hp and .5-1mpg over stock. plus it makes a really cool noise as the air flows throught it. kinda sounded like i had an air shifter...lol

My mileage was at 10mpg in city and interstate. The thing that helped me was I started using Lucas Ethanol Treatment. It increased my mileage to 16.5 to 17.5. I am getting 17.2 mpg from my house to Birmingham,AL (100 miles) with the ac running and going 70 mph.

Getwired said:

:yesnod: Agreed -- intake and programmer (plus synthetic oil and 93 octane fuel) have gotten me a nearly 35% improvement over stock mileage. Jury's out on the throttle body spacer tho -- seems lots of people think they're useless on a fuel injected vehicle, which is why I won't get one. The Denali already has a 3.5" exhaust system (can't see improving on that with my ride until someone comes out with a dual system for the 6.2L). Good luck!

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I tried using higher octane fuel and my mileage went down. Each engine is different. Use the octane that give you your best milage. In my case I get the best mileage with 83 octane, and as far as syntheic oil use what you are most comfortable I drive a big rig at 500 thousand miles I decided to change to syn. AT 550 thousand miles it blew up. It was determined by the mechanic that the syn oil was the cause for the blow up. 250 thousand dollars later, I done a bunch of other work on the truck while it was down.) I am back on the road. I WILL NOT EVER PUT SYN OIL IN ANOTHER MOTOR!! But that is only my take on syn oil. Decide for yourself.

Man, so much bad info on in this thread from 10 years ago. If you want to improve the fuel economy, shorter, smaller, narrower, harder rubber tires on your rig. Lower it also. THAT will increase your mileage. K&N filter is just BS that will actually cost you more in the long run if you follow cleaning procedures you will eventually F up your MAF.

The best thing to do would be take it to one of the few that can do a custom tune. GM has always left a lot on the table for warranty reasons. Get that timing advance a little more realistic (and in later years, ditch the TQ Management) and your probably up 2 - 3 MPG, no other changes. But the average Joe or backyard mechanic isn't going to make that happen.

Milage

I can only tell you what I am getting. There is no bs in my post. eace:

I'm curious how the mechanic determined that the Synth Oil caused motor to blow?

It was taken to the dealership,so I don't know how they figuered it out.