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I recently purchased this 2002 Trailblazer LT 4x4 all stock with automatic transmission with Vortec straight 6 cylinder. I changed out all fluids rearend, tranny, engine, front diff, transfer case, spark plugs AC Delco, all 6 coils, cleaned the throttle body,replaced both O2 sensors,replaced air filter, lubed all grease fittings, tire pressure is correct, No engine codes, not burning oil, runs great, idles great. It's getting 12 miles per gallon in town as per hand calculated miles per gallon and I drove it like a grandma to try and get good fuel mileage and I ran a can of seafoam in it prior to changing O2 sensors. I have noticed the muffler is looking like it needs replaced just due to the looks of it. No exhaust leaks. This Trailblazer is 100% stock no aftermarket parts. Any suggestions to get better fuel mileage? Thank you
 

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2004 chevy trailblazer_lt
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You can try this - Disconnect your battery for about 60 minutes then reconnect it. This will cause the PCM to "forget" it's learned driveability memory. Start driving around normally so the PCM "relearns" your driving characteristics, and see if your gas mileage improves. It is an old trick that often works. However, there are no guarantees. Most of the people I know who have done this have seen improvements in their gas mileage, but a few saw no change.
 

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Thank you for your reply. After running a can of seafoam through it. I drove it 400 miles about 50% hwy driving about 40% city driving and 10% mountain driving. The hwy driving was averaging about 75 mph and city driving was 25 mph and hand calculated out to 16 miles per gallon. If it stays like that I can live with it. If you use a scan/code reader and clear your codes is that the same as disconnecting your battery
Thanks again
 

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2004 chevy trailblazer_lt
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Go ahead and try the battery disconnect trick - you just might pick up a mile or two per gallon. I routinely get over 19 MPG on the highway and ~14 MPG in town driving.

Yes, you can clear codes with a scan/code reader. It's the same as disconnecting the battery except you won't lose "learnable" memories in the PCM.

Good Luck!
 

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2008 chevy trailblazer_lt
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Does the power seem normal or maybe low? When I had a bad catalytic converter in a Kia Sportage, mileage went down and power went way down (and the exhaust sound was quieter, but I didn't notice until the cat was replaced). Does the heater work normally? My 6.7L small block had mileage that went from 16 mpg on the highway with 20w-50 oil and 160 degree thermostat, to 19 mpg with 195 thermostat and 10w-30 oil. In our HHR, I've suspected that it has always had a leaky injector or injectors, as the oil seems to always smell like gas. I'd wonder how well it coasts, (like in neutral) as an indicator of brake, bearing, tire drag. Any chance front hubs don't unlock or 4x4 stays engaged? We probably average 19 mpg with our 2008 4.2L 2WD Trailblazer, mostly highway.

Rob in AZ
 

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Discussion Starter #6
Go ahead and try the battery disconnect trick - you just might pick up a mile or two per gallon. I routinely get over 19 MPG on the highway and ~14 MPG in town driving.

Yes, you can clear codes with a scan/code reader. It's the same as disconnecting the battery except you won't lose "learnable" memories in the PCM.

Good Luck!
I just did the battery disconnect yesterday afternoon so next time out I will recheck fuel mileage. This vehicle isn't an everyday driver. Bought it just to have something to tow our snowmobiles and to get out of my diesel work pickup once in awhile. But my 2006 Ford F250 6.0 diesel 2 wheel drive gets 16 mpg city and 19 mpg hwy so I did expect to get better fuel mileage with a 6 cylinder trailblazer.
 

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Does the power seem normal or maybe low? When I had a bad catalytic converter in a Kia Sportage, mileage went down and power went way down (and the exhaust sound was quieter, but I didn't notice until the cat was replaced). Does the heater work normally? My 6.7L small block had mileage that went from 16 mpg on the highway with 20w-50 oil and 160 degree thermostat, to 19 mpg with 195 thermostat and 10w-30 oil. In our HHR, I've suspected that it has always had a leaky injector or injectors, as the oil seems to always smell like gas. I'd wonder how well it coasts, (like in neutral) as an indicator of brake, bearing, tire drag. Any chance front hubs don't unlock or 4x4 stays engaged? We probably average 19 mpg with our 2008 4.2L 2WD Trailblazer, mostly highway.

Rob in AZ
Power is great and no smells at all. I might change out the catalytic converter down the road but as long as it throws no codes leaving it alone. This Trailblazer isn't an everyday driver. Thank you for the suggestions
 

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2006 chevy trailblazer_lt_ext
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You are not too far off from norm.
I have a 4.2L I-6 LWB and get about 14-16 mpg depending on how hard I get on it. I can get 19-21 on the highway.
If you have a scan tool, look at short and long term fuel trims and investigate any reading +/- 10%.
 

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Best I ever got was about 20 highway. Mine usually hung in the 15-16 range with mixed driving. These aren't well known for being economy models. But they do go in the snow...
 

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2004 TrailBlazer LS 4x4
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I recently purchased this 2002 Trailblazer LT 4x4 all stock with automatic transmission with Vortec straight 6 cylinder. I changed out all fluids rearend, tranny, engine, front diff, transfer case, spark plugs AC Delco, all 6 coils, cleaned the throttle body,replaced both O2 sensors,replaced air filter, lubed all grease fittings, tire pressure is correct, No engine codes, not burning oil, runs great, idles great. It's getting 12 miles per gallon in town as per hand calculated miles per gallon and I drove it like a grandma to try and get good fuel mileage and I ran a can of seafoam in it prior to changing O2 sensors. I have noticed the muffler is looking like it needs replaced just due to the looks of it. No exhaust leaks. This Trailblazer is 100% stock no aftermarket parts. Any suggestions to get better fuel mileage? Thank you
My 04 does the same thing when the fuel filter has 15-20k on it. Replace the fuel filter and that may help.
 

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2008 gmc envoy_slt
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I recently purchased this 2002 Trailblazer LT 4x4 all stock with automatic transmission with Vortec straight 6 cylinder. I changed out all fluids rearend, tranny, engine, front diff, transfer case, spark plugs AC Delco, all 6 coils, cleaned the throttle body,replaced both O2 sensors,replaced air filter, lubed all grease fittings, tire pressure is correct, No engine codes, not burning oil, runs great, idles great. It's getting 12 miles per gallon in town as per hand calculated miles per gallon and I drove it like a grandma to try and get good fuel mileage and I ran a can of seafoam in it prior to changing O2 sensors. I have noticed the muffler is looking like it needs replaced just due to the looks of it. No exhaust leaks. This Trailblazer is 100% stock no aftermarket parts. Any suggestions to get better fuel mileage? Thank you
The biggest thing people forget is that gearing has a LOT to do with fuel mileage. Check your RPO codes in the glovebox to see what rear end ratio is in it. I have a 2004 Envoy (Auto/6/4x4) with 4.10 rear that gets 16 hwy and 14 city and a 2007 Envoy with 3.42 rear that gets 22 hwy and 18 city. Both of them are identical except for color and rear end ratios.
 

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2003 gmc envoy_slt_xl
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Be sure to check or have your mechanic check your transfer case fluid level. My transfer case ran totally dry (never had it looked at) and one day, it said, "Bye bye". The rest of the vehicle wasn't worth everything it would take to replace it with a reconditioned one. Perhaps having the fluid changed in that might help lesson some resistance in that part of the powertrain. With over 250k miles on it, my V8 Envoy was usually around 20mpg. I think the sticker was 19 hw and less city.
 

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2006 chevy trailblazer_ls
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I recently purchased this 2002 Trailblazer LT 4x4 all stock with an automatic transmission with Vortec straight 6 cylinders. I changed out all fluids rearend, tranny, engine, front diff, transfer case, spark plugs AC Delco, all 6 coils, cleaned the throttle body, replaced both O2 sensors, replaced air filter, lubed all grease fittings, tire pressure is correct, No engine codes, not burning oil, runs great, idles great. It's getting 12 miles per gallon in town as per hand calculated miles per gallon and I drove it like a grandma to try and get good fuel mileage and I ran a can of seafoam in it prior to changing O2 sensors. I have noticed the muffler is looking like it needs replaced just due to the looks of it. No exhaust leaks. This Trailblazer is 100% stock with no aftermarket parts. Any suggestions to get better fuel mileage? Thank you
That's about right Don't know if can get any better gas mileage
 

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2005 saab 9_7x
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When was the last time you changed the fan clutch? A fan clutch that is weak/failing has a number of nuanced symptoms, including a decrease in fuel economy. It's not a cheap part, though, so the ROI may not be good enough for you now.
 

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2002 chevy trailblazer_lt_ext
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I recently purchased this 2002 Trailblazer LT 4x4 all stock with automatic transmission with Vortec straight 6 cylinder. I changed out all fluids rearend, tranny, engine, front diff, transfer case, spark plugs AC Delco, all 6 coils, cleaned the throttle body,replaced both O2 sensors,replaced air filter, lubed all grease fittings, tire pressure is correct, No engine codes, not burning oil, runs great, idles great. It's getting 12 miles per gallon in town as per hand calculated miles per gallon and I drove it like a grandma to try and get good fuel mileage and I ran a can of seafoam in it prior to changing O2 sensors. I have noticed the muffler is looking like it needs replaced just due to the looks of it. No exhaust leaks. This Trailblazer is 100% stock no aftermarket parts. Any suggestions to get better fuel mileage? Thank you
I have an 2002 trailblazer lt I get around 17-18 on the highway @ 75mph. I don't drive city too much so I don't know what that is.
 

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2008 chevy trailblazer_lt
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I have an '08 LT 4WD with 87k miles. Regularly get 15.5 to 16 in the city, and 19 or so highway - 20 on a good day when I'm going slower than 75..
 

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2002 chevy trailblazer_ltz
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Not sure what you're expecting but these are a box trying to cut through the air with an inline 6. A tad underpowered and pending on your terrain youre not far from normal.

I live in PA and that's about a typical average for that vehicle in this state. Too many hills
 
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