Why is my 2004 EXT LT trailblazer burning too much gas.

Asked by Jan 13, 2014 at 02:32 PM

Question type: Maintenance & Repair

I have noticed that over the past few months the blazer has been getting less and less
mpgs. There are no codes and if has passed the required emissions test in my state. It
does not run bad. It idles really well and there is no signs of why it is burning more gas.

15 Answers


Hello, How much of a change in MPG? Have you been experiencing bitter cold temps or seasonally cool temps (winter)? This can cause your MPG to drop especially if you drive shorter distances. It takes more fuel for a cold engine to run than a warm one & your engine management system works at peak performance after the oxygen sensors (in the exhaust) have reached temp....


Also with the cold air, your tires pressure will drop at least 5psi or more. Make sure to check them, they might be low.

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Your spark plugs need changed. Once they get a larger gap it takes more gas to fire the cylinder. Dirty air filter and tire pressure will cause it too.

This has been going on since it was warm out. Tire pressure is fine. It is not that cold here. My spark plugs were checked and they are fine. A complete OEM diagnostics has been run and nothing can be determined that could be causing the drastic fuel consumption. It is getting around 11 to 12 mpg compared to 16+ in the city. Road driving hasn't changed that much.


Do you have 'check engine' or 'tailpipe' emissions testing in your state?

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Also how long are you driving for and what are the air temps? Has low fuel economy persisted while experimenting with other fuel companies?


Winter gas. They put additives in it and it kills everyones fuel mileage.


I've been having the same issue. Dropped from 17 mpg to 10 mpg and I can't figure out why. No codes and no check engine light. Tire pressure is good. I've replaced the spark plugs, fuel filter, fuel pressure regulator, and o2 censor. Tried running 6 tanks of non ethonol fuel too. Nothing seems to help. I'm at a complete loss as to why the milage took such a hit. And it's getting 10 mpg all year long..winter, spring, summer, fall.

7 people found this helpful.

2005 Trailblaser with the same problem, runs and idles fine but millage took a dump. I used to get over 300 miles a tank now I get less than 150 miles a tank? Someone has to know what is going on?

2 people found this helpful.

I see no answers here and this hasn't been helpful at all... I'm getting hardly 10 mpg... Can anyone explain what's going on? I had a friend that had a similar size SUV of another maker (Pacifica) experiencing the same horrible gas mileage everyone was thinking transmission, tune-up whatever; however, they vehicle showed a code for the catalytic converter during the complete computer diagnostic test … Sure enough order the item had it installed ..WHAM-O… problem solved.. Does anyone know what solves this problem for the 2003 Trail Blazer 4.2ltr? Please help a single mother three kids and things are not going well and need the help seriously.

I have Trailblazer LT 2004, I have the same gas problem, and I have no idea what to do with it !! can anyone help plz.


I have a 2005 ext trailblazer and have never gotten less than 16.5 mpg city and no less than 21.3 on the highway loaded down. Every 6 months, I pull the throttle body completely off and clean it back to silver, I run a full k&n intake and euridium plugs gapped at .040 and only premium fuel. The new window sticker says 14 mpg city and 18 mpg highway this is why complaints of 12-15 mpg make no sense especially if proper matainance isnt done just saying

I have the samer problem with a 2008 TB. Cleaned a filthy Throttle Body and still a problem. Went to a muffler shop and he said the Cat Conv was at 700 degrees and normal should be around 350. I had them replace both of them today 8/18/2017. Filled the gas tank and waiting to see what happens. Wish me luck

New Cat didnt help at all. $750 down the drain


That would be because a cat running 700 degrees isn't that far fetched as mine runs 650 degrees and after routine maintenance including proper .045 plug gaps on uridium plugs, cleaning the 4" k&n filter and piping, the throttle body cleaned off the manifold and iac as well as tps cleaned and reassembled and lastly the map sensor and deleted the valve cover vent tub in favor of a similar stand alone breather much like what came in the cold air kit for my gs-r and my sr/t 4. The latest calculation is 19.1 mpg on ethanol free fuel on the street. We are taking a trip next weekend. The last trip in the dead of summer yielded 21.3 mpg on the highway on premium fuel. I'm expecting somewhere in the same neighborhood this trip. Please keep in mind that I have the rwd ext model. I have done the exact same procedure on a friend 4wd trailblazer ls swb and it only did 19 mpg on the hwy and 17 mpg on the street. The driver of this particular trailblazer loves higher rpm and likes to make 40mph-100mph pulls often so I'm not surprised. The difference in hearing is the ultimate deciding factor as obviously 80mph @ 1800 ish rpm is alot more efficient than the same 80mph @ 2500-3000 rpm.

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