Gas milage has fallen off by almost 30% in one month! Any ideas?

I have a 97 Blazer that used to get about 320 miles to a tank up until about 2 months ago. Now all the sudden it is getting about 250! What happened? The fact that the milage fell off so sharply in such a short period of time points to something being broken or out of wack doesn’t it? I have gotten 250 miles or so out of my last 7 tanks, every tank before that was at least 300 but mostly I would push it to around 330. There was no gradual decrease. I immediately noticed that I was filling up eveyr week instead of week and a half.

What the heck happened? Should I take it in for a tune up? Is the computer messed up? Anyone have any ideas?

Do you warm it up longer in the morning lately? Do you drive in stop and go traffic more often lately than freeways? Are you filling your tank, or stopping when the nozzle stops?

There are many reasons this can happen. You may have to clean your fuel injectors, for one. Dump a bottle of injector cleaner ($2-3)into your tank next fill up and see if that helps.

That’ll be $75.

Has performance fallen off?

Performance seems to be the same. I drive it really hard, but I always have. I don’t warm it up in the morning, never have.

Does injector cleaner really do anything? I had heard that it really doesnt clean too much.

It just seems like there is a real problem in there somewhere for the mileage to fall off so sharply and so quickly.

Check:

Air Filter
Spark Plugs
Ignition System

Change the air & breather filters. It’s easy & cheap.

Tune-ups are good.

ask your mechanic to check your vacuum line.

Also check tire pressure: one or two low tires can put quite a drag on a car.

Right, tire pressure is a big deal.

Also, it could be your converter, or any myriad of emmission control devices. They usually show up as the “check engine” light though. Has the light been coming on, even for a short time? Could be that the light doesnt work. I would take it to an "Auto Zone" or similar store that checks the engine light for free. They walk out to the car with a hand held device that connects to the computer in your vehicle and displays any trouble that the computer has detected. Its free because they figure you will buy the part from them if you`re going to replace it.

Did you forget to mention the boat you’ve been towing for the last two months?:smiley:

Other things to check:

Thermostat - engine might not be getting up to temperature
Temp sending unit - could be confusing computer about current operating temp

Usually if the computer is futzed the check engine light will come on. Ditto if one of your sensors has failed. Connecting it to one of those hand held scanners that whickfistle mentioned will show if the computer is malfunctioning. I don’t know what other info you can get out of a handheld scanner like that, but look for anything out of the ordinary (like it thinks the engine temp is -20 deg F and it’s 70 deg outside).

Auto Transmission? is it locking up in overdrive?

check the plugs, the gaps do get bigger

are you sure there is no gas leak?

Is the kid down the street sucking out a gallon now and then?

[ul]:smiley: [sup]Maybe your odometer is broken.[/sup][/ul]

I don’t if you do any offroad or other rough driving, but is it possible you dented you gas tank? I did that to a gf’s mom’s blazer in HS and it would run out of gas at 1/3 tank, instead of going empty…
I guess that’s not the same thing. Has your mileage per gallon dropped, or just you mileage per tank. That’s one more way to measure.

Stopping when the nozzle stops is filling. Continuing after that is overfilling. To acheive the same result, simply pull the nozzle out and squirt in on the ground.

A tune up would be the first line of defense. You may have one or more cylendars not firing (You can usually feel if it’s more than one, but in a V8 you may not)

In my car (89 Cavalier), my wifes car, and any other car I have ever owned, when the nozzle stops, you can still get another gallon or so in the tank. In PA, we have some self serve stations with the notches on the handle so you don’t have to stand there and continue to squeeze. Some states, I know, do not. (In NJ, for one, it is even illegal to pump your own gas). When the tank is just about full, the handle stops pumping. This is a safety feature to prevent spilling fuel onto the ground. This does not, however, necessarily mean that the tank is full. Some handles are very sensitive, some are not set properly, and shut off early.

You can hear when the fuel tank is full to avoid overfilling the last gallon.

You may think your tank is full when the nozzle shuts off, but it really isn’t. That is why YMMV.

well, I could come up with a few cites [url=http://www.dep.state.pa.us/dep/deputate/airwaste/aq/factsheets/fs_yourcar.pdf]that state otherwise.

another witty retort killed by bad coding.:smack:

Thank you for pointing out that something I have been doing for the last 20 years (I thought with no ill effects) is not only environmentally unsound, but a waste of money, and potentially damaging to my car.

I will give you a chance to redeem yourself on the coding:
I clean my ears by inserting the Q-tip into my ear canal, where it tends to get dirty…:eek:

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