Looking for MPG with possible side effect of power

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I recently bought a 99 yukon 5.7 SLT cherry with 53K

It is in Utah. temps for the last month have been high of 38 low of 3 Fahrenheit. I typically drive at night where temps are 30-5. the truck has a cold air intake and 285/75r16 tires. other than that its stock.

the temp gauge sits 150-160. my fuel at the pump comes to 11.25 - 12.75 mpg without adjusting for tire size, just dividing gallons pumped by miles on odo. I drive about 50/50 in highway/city. I tend to accelerate/decelerate slowly but hold high speeds on the highway ( I don't intend to change this). I might start off a trip with 800 lbs. (estimated) then return empty (+me).

I am mainly looking for better MPG with possibly better response. I am considering a superchips flashpaq on MPG tune, a 195 degree stat, and maybe a MBRP or "complete" cat back exhaust ( the last for performance, not looks or sound ).

reasoning:

flashpaq: not heard individual or in person response but all reviews seem to like power and gain about 2 mpg, some say more but I tend to believe exaggeration. + synergistic effect of intake & cat back + tune overall performance.

thermostat: I understand the higher temp gets better efficiency and is better for the motor and cat, or cats. and 1-2 MPG increase

Exhaust: mainly completing intake + exhaust combo. as well as the complete synergistic effect with the superchip tune.

Any info for or against any of these plans would be very helpful. Any other ideas you have would be great. I hope to keep this ride for 200K or more.

Thanks guys!

this is my first post, don't kill me yet!

 

[josueh95]

get a black bear tune instead of the flashpaq tune it will give you a nice hp gain as well as some MPG they are a vendor here..also a free flowing exhaust with lt headers will help out

 

[autolover3]

If you get headers don't delete the EGR!

Also I recommend the Blackbear tuned PCM also. I have one and love it.

Longtubes or shorties will be a improvement over stock headers, run a aftermarket muffler and if you want maybe high flow cats.

What size tires do you have also?

That 12 mpg you are getting is the average I'd say with these beasts. Your driving a brick down the road. Just keep the good driving habits up and a few modifications might help. Also look into the E-fan conversion sticky on here.

 

[aj713]

I have a cold air intake and 160 thermostat. It was a noticeable improvement in power, but not really in mpg. I changed the plugs to e3- that made all the difference.


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[SunlitComet]

uh yeah, keep the intake, change your thermostat back to the required 195 degrees type and just use delco 41-993 or autolite xp605 plugs. You are going to foul up your cylinders and burn thru a lot of gas with with the current thermostat alone. it will also ruin your egr ports and cats a lot quicker.

 

[pmackiniv]

If you get headers don't delete the EGR!

Also I recommend the Blackbear tuned PCM also. I have one and love it.

Longtubes or shorties will be a improvement over stock headers, run a aftermarket muffler and if you want maybe high flow cats.

What size tires do you have also?

That 12 mpg you are getting is the average I'd say with these beasts. Your driving a brick down the road. Just keep the good driving habits up and a few modifications might help. Also look into the E-fan conversion sticky on here.

What are some concers one should have putting on headers as far as valves go?


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[autolover3]

1 decision will be if you want stainless, ceramic coated, bare steel etc. Longtubes will most likely need custom exhaust made up for vehicle.

Longtubes vs shorties, I would say personal choice but LT's offer a slight gain over shorties but both are better than the stockers. Also check if they are made with egr ports, air injection ports if your vehicle has it. And run copper gaskets with headers to help reduce leaking.

 

[SunlitComet]

ceramic coating should be an absolute must.