Getting 8.5 mpg need help

[BlueCollarTahoe]

gonna give it a month straight and see where its at in july. i got the "tighten gas cap" message today i checked and the hoses aeew all connected still. well see what happens.

 

[BlueCollarTahoe]

LONG UPDATE:

been a while since i updated this and ive come to the conclusion that 8.5 is normal. I spent a week or so in another state..very rural part of PA...highwaY driving and country roads with no lights....when i went to refill the tank out there i was getting an estimated 340 miles per gallon. the gas lasted so much longer. the drive back to nyc resulted in a fill up...highest i ever saw...371 miles for the tank estimated. once i got back to the stop and go city driving...back down to 220...200..210. its the stop and go that really kills this truck. i got the emissions code out there...slight smell of gas with the AC on and wehen i throttle the pedal so there is defintiely leak somewhere in the lines...will fix soon.

 

[swathdiver]

LONG UPDATE:

been a while since i updated this and ive come to the conclusion that 8.5 is normal. I spent a week or so in another state..very rural part of PA...highwaY driving and country roads with no lights....when i went to refill the tank out there i was getting an estimated 340 miles per gallon. the gas lasted so much longer. the drive back to nyc resulted in a fill up...highest i ever saw...371 miles for the tank estimated. once i got back to the stop and go city driving...back down to 220...200..210. its the stop and go that really kills this truck. i got the emissions code out there...slight smell of gas with the AC on and wehen i throttle the pedal so there is defintiely leak somewhere in the lines...will fix soon.

Very similar with mine too Jay. Most of errands are within a few miles of home and there are so many lights and stop signs there's usually not more than a quarter mile between them. It just tanks the mileage. It now averages 20 mpg @ 65 mph but drops to 18 @ 70 mph and 17 @ 75. Keep us posted about that smell/leak, that's going to cost some too.

 

[bottomline2000]

LONG UPDATE:

been a while since i updated this and ive come to the conclusion that 8.5 is normal. I spent a week or so in another state..very rural part of PA...highwaY driving and country roads with no lights....when i went to refill the tank out there i was getting an estimated 340 miles per gallon. the gas lasted so much longer. the drive back to nyc resulted in a fill up...highest i ever saw...371 miles for the tank estimated. once i got back to the stop and go city driving...back down to 220...200..210. its the stop and go that really kills this truck. i got the emissions code out there...slight smell of gas with the AC on and wehen i throttle the pedal so there is defintiely leak somewhere in the lines...will fix soon.

I didn't read through the whole thread but have you pulled the vacuum line off the fuel pressure regulator? If you see fuel then the regulator is bad. Also have you put a pressure gauge on the fuel line to see if it's dropping pressure at the rail? Could be a stuck injector.

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[BlueCollarTahoe]

I didn't read through the whole thread but have you pulled the vacuum line off the fuel pressure regulator? If you see fuel then the regulator is bad. Also have you put a pressure gauge on the fuel line to see if it's dropping pressure at the rail? Could be a stuck injector.

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yes its been checked multiple times...normal. there is no regulator on the fuel rail i checked and was gonna replace it but it isnt there.

 

[sonic_the_hedgeh]

I had some fuel economy problems as well. Did and intake clean of my throttle body. Also I found under the plastic cover on top of the engine, a built in pcv valve and line. I cleaned through the hole into the engine and that helped a lot.

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[sonic_the_hedgeh]

Also I did try some Lucas lubricants Fuel additive. Works really well. Around town my Yukon is a lot better on fuel than before.

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[swathdiver]

Also I did try some Lucas lubricants Fuel additive. Works really well. Around town my Yukon is a lot better on fuel than before.

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From what to what?

 

[sonic_the_hedgeh]

From what to what?

I haven't actually measured it but I did try an experiment for the past 6 months. Instead I add 2 to 4 liters of 5w30 to the tank of fuel and again much Better fuel economy. On one trip going just over 300 km's I used quarter tank of fuel.

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[sonic_the_hedgeh]

Update. So far I will complete my year of testing using oil instead of Lucas lubricants. Cheaper does the same thing. In colder weather use 5w30. I have used up to 10w40 and used 2 to 3 liters per tank and works great. Exhaust is still clear and fuel is lasting much longer.

Haven't tested yet in winter weather but this winter it should work fine even with minus 30 celcius. I will use 0w20 for that cold.

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