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Discussion Starter #1
I changed my fuel filter a few days ago. It was not the original, but I oculd tell that it had been there a good long time. I replaced it with a filter that had the same quick-connect fittings for the car. Took about 5 minutes.

The difference? Slightly smoother, but I'm seeing almost 2mpg better mileage (from 20.2 -> 22.2 in mixed driving)! Why? Well, I can't attribute it only to the fuel filter, but my thoughts are that the old filter was very restrictive. This forced the ECU to have the injectors opened longer to get the right amount of fuel in... with 8 injectors, it probalby had the fuel settings all tweaked to compensate. Changing the filter is allowing it to get the right volume of fuel and, as such, brought it back to the fuel consumption rate that it should be at.

For a $7 part, this has already paid for itself!
 

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so, on a 1997 eldorado, is there one or two filters ?

where are they located??
is one perhaps in the gas tank itself ?

thanks,
kevin
 

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Dang, I'd settle for 20mpg mixed. I'm (my wife is) getting 17.5. Mostly in town though. You must be doing more highway time.
I'm not sure the filter helps(hurts) that much. It would be interesting to note the fuel pressure before and after. Still, it's a good idea to replace the filter every so often. They are cheap enough.
 

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Discussion Starter #4
On these cars, the filter is located underneath the driver's side rear passenger, right in front of the wheel. It unbolts, un-hooks and goes right back into place.

I am having a hard time believing the filter makes that much of a difference, too. However, I've changed nothing. Not the brand of gas, not the way I drive, not where I drive, nothing except the filter. Instead of seeing ~450 miles per tankful (based on the computer's estimate), I'm now seeing ~530 miles...

And I do a lot of highway time, but it's mixed with a lot of quasi-city driving (not exactly stop and go, but close). I have been disappointed with the mileage so far, it should get better than 20mpg, but I'd be very happy with 22... that's just about what these things got new.
 

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Wait, that doesn't make sense to me... If the old filter was restrictive, wouldn't it make less gas go through the engine? I would buy that the new filter is more restrictive than the old rather than the other way around. :hmm:

Still, its good to get more MPG.
 

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Discussion Starter #6
A more restrictive filter is going to make the fuel pump work harder to get the fuel to the engine, once it gets to the engine, the volume and pressure will be less than it should be. To compensate for the decrease in fuel pressure, the ECU will keep the injectors open for a longer period of time to get the right amount of fuel into the car (monitored by the O2 sensor, etc.). With larger injector latency, the chances that some cylinders are goign to be flowing too much fuel increases... so it will use more gas in a less efficient way...

That's the theory, at least...
 

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I beleive the theory is correct, just my opinion. Changing the fuel filter regularly is essential to the well being of most any fuel injection system. I think the value of good filters has been discounted by many unfortunately. As you have said, it's very inexpensive maintenance. Maybe that's why folks don't give it much creedence.
 

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tremor12 said:
A more restrictive filter is going to make the fuel pump work harder to get the fuel to the engine, once it gets to the engine, the volume and pressure will be less than it should be. To compensate for the decrease in fuel pressure, the ECU will keep the injectors open for a longer period of time to get the right amount of fuel into the car (monitored by the O2 sensor, etc.). With larger injector latency, the chances that some cylinders are goign to be flowing too much fuel increases... so it will use more gas in a less efficient way...

That's the theory, at least...

Good theory, it makes sense now. I should go change my fuel fiter soon, 89k miles and I think it might be the original filter... :eek:
 

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It's also possible that the next tank of gas you got was the normal blend and not summer blend gas. Summer blends have more alcohol, which you need more of to achieve a stoichiometric air/fuel mix. Long story short, if you were running on summer blend before, it's very possible your mileage would have been 2 MPG less than it is now with the normal blend. The filter probably has nothing to do with it.
 

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Yeah, while I am far from an expert, I would have to bet against the fuel filter having anuthing to do with fuel milage.
 

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mcowden said:
It's also possible that the next tank of gas you got was the normal blend and not summer blend gas. Summer blends have more alcohol, which you need more of to achieve a stoichiometric air/fuel mix. Long story short, if you were running on summer blend before, it's very possible your mileage would have been 2 MPG less than it is now with the normal blend. The filter probably has nothing to do with it.
Hmmm? Don't know anything about your area, but in the northwest in some of the bigger city areas our winter fuel is blended with alcohol to keep the emmissions lower, not the summer time.
 

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maxtorque02 said:
Hmmm? Don't know anything about your area, but in the northwest in some of the bigger city areas our winter fuel is blended with alcohol to keep the emmissions lower, not the summer time.
I'm not sure what purpose that would serve. They put alcohol in the fuels almost all the time, but in the summertime they use more alcohol content to cut down on volatility. Vaporized hydrocarbons form smog, and that happens mostly in hot, sunny weather, not in the wintertime, so if they have a winter blend fuel, it's the stuff they use all the time except summertime most likely.
 

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Discussion Starter #13
maxtorque02 said:
Hmmm? Don't know anything about your area, but in the northwest in some of the bigger city areas our winter fuel is blended with alcohol to keep the emmissions lower, not the summer time.
I don't know what the blend is, but the winter formulation gives a 10% DROP in fuel economy across the board... 200 miles on this tank, in my normal driving cycle and I'm still averaging 22.1... up almost a full 2.
 
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