Terrible Fuel Economy

[FirebirdHatesRice]

Over the past few months I've been calculating my fuel economy every time I get gas. On average, I'm getting around 200 miles per tank. It's terrible, and I'm not driving with a heavy foot either. For the most part, I don't think I've had better than 15-16mpg....this with a cat back exhaust and a cold air intake. What can be to blame for the terrible fuel economy? Spark plugs/wires? any suggestions?

[Camaro_SLP]

If your exhaust is opened up enough, you could be losing gas mileage due to that..Don't assume because you got an aftermarket exhaust, you get better gas mileage. How old are your spark plugs and wires? Change those out, along with your fuel filter. That is one of the most neglected filters in the car. Get a full tune up, run an injector cleaner, and continue to drive normal.

[hockeyman]

If your spark plugs'n wires haven't been changed in a few years or over 50k, then that would probably help in better fuel econ.
Also, whenever I change my oil, I always put a bottle of fuel injector cleaner in my tank. Just as a preventive maintenance insurance.

-Marc

[speedy-v6-camaro]

PCV Valve?

[cassie]

I get about the same gas mileage. I do 100% city driving.

[FirebirdHatesRice]

<blockquote>quote:</font><hr>Originally posted by Camaro_SLP:
If your exhaust is opened up enough, you could be losing gas mileage due to that..Don't assume because you got an aftermarket exhaust, you get better gas mileage. How old are your spark plugs and wires? Change those out, along with your fuel filter. That is one of the most neglected filters in the car. Get a full tune up, run an injector cleaner, and continue to drive normal.<hr></blockquote>

The exhaust has the stock I pipe, all I did was put on a new muffler and exit pipes, so I don't think I would have opened the exhaust enough to make that big of a difference. As for the spark plugs, wires, and fuel filters...how can I check to see what kind of condition they're in?

[Camaro_SLP]

<blockquote>quote:</font><hr>Originally posted by FirebirdHatesRice:


The exhaust has the stock I pipe, all I did was put on a new muffler and exit pipes, so I don't think I would have opened the exhaust enough to make that big of a difference. As for the spark plugs, wires, and fuel filters...how can I check to see what kind of condition they're in?<hr></blockquote>


How long have you had your car? If you haven't changed them since you bought the car, you mine as well change them. For the spark plugs you can simply pull one out and look at it. If it's all black and gunky looking, change them. You're fuel filter you mine as well replace instead of checking to see if you need to. Once you have it off, it's not worth the pain to 'just' check it. All together, it should cost maybe a little over $100 for plugs, wires, and filter.

[FirebirdHatesRice]

<blockquote>quote:</font><hr>Originally posted by Camaro_SLP:



How long have you had your car? If you haven't changed them since you bought the car, you mine as well change them. For the spark plugs you can simply pull one out and look at it. If it's all black and gunky looking, change them. You're fuel filter you mine as well replace instead of checking to see if you need to. Once you have it off, it's not worth the pain to 'just' check it. All together, it should cost maybe a little over $100 for plugs, wires, and filter.<hr></blockquote>

I bought the car last year with around 76,000 miles on it. Right now it's just a bit over 83,000. I've been meaning to get the spark plugs and wires replaced for awhile just as a precaution. Any reccomended brands?

[ November 09, 2003: Message edited by: FirebirdHatesRice ]</p>

[Bliggida]

Just get a quality name brand and they'll be fine. At your performance level no particular wire is going to make a difference over another brand.
Now at 500 HP with an MSD ignition, Pro-Mag distributor, and Blaster coil, that's a different story. Plugs and wires could reveal 5-10 more horsepower.

- I would start with your plugs and wires, they will probably be the cheapest.
- Ensure your air filter is clean, and also
- may want to get a new fuel filter, should be less than 10 bucks.
After those if it's still not any better. Start looking at your O2 sensors, and EGR. They will be more costly to replace. 02 sims may be cheaper than new 02 sensors, so check on that?!

After I got my motor back together, the tank was full and sat for 5 months. I got about 10 MPG.
So the next 3 tanks I ran 93 octane with a fuel injector cleaner, before resuming to regular 87 octane.
I'm getting an average 23-24 MPG overall city and highway with 300-340 miles per tank. Thats with getting on it at least once a day.
I noticed I drive just as aggressive now that I own the car, pay for insurance, and the gas for it.
Everyone said I wouldn't when it costed me.
They said the same about the tires on my Z28. But I held a burnout contest at work when they were a week old.

Check on the cheaper things first and see what happens.

Camaro SLP, an unrestrictive exhaust would not hurt your gas mileage (not like that). Perhaps once I order my QTP cut-out, I'll run it open for a full tank and show you the results. At worst it'd probably be around 21-22 MPG, losing 1 or 2 mpg total.

[ November 09, 2003: Message edited by: Bliggida ]</p>

[Camaro_SLP]

<blockquote>quote:</font><hr>Originally posted by Bliggida:
Camaro SLP, an unrestrictive exhaust would not hurt your gas mileage (not like that). Perhaps once I order my QTP cut-out, I'll run it open for a full tank and show you the results. At worst it'd probably be around 21-22 MPG, losing 1 or 2 mpg total.
<hr></blockquote>

If you run straight pipes from the motor back, you will definetly lose gas mileage. No/little back pressure = loss of gas. A cut-out, you won't lose as much..

[Bliggida]

I don't know about your definition, but a cut-out to my understanding means placement is just after the exhaust manifolds or headers. It don't get much more open, than open headers!!!

[Camaro_SLP]

<blockquote>quote:</font><hr>Originally posted by Bliggida:
I don't know about your definition, but a cut-out to my understanding means placement is just after the exhaust manifolds or headers. It don't get much more open, than open headers!!!<hr></blockquote>

I see your point. You will lose gas mileage with a cut-out, but it should not be dramatic enough to get HORRIBLE gas mileage. My initial point was to say that a free flowing exhaust does not necessarily help gas mileage..

[ November 10, 2003: Message edited by: Camaro_SLP ]</p>

[Ian]

one time i was gettin horrible gas mileage. i did the plugs, oil change, fuel filter, and PCV valve.

i went from 18mpg to 31mpg on the highway. quite the difference.

fuel filter and PCV would probably be the biggest cause of shotty gas mileage. do a total tuneup with the PCV and fuel filter, and go from there.

[FirebirdHatesRice]

Well, just got back from from Jiffy Lube. Oil change, new PCV valve and new fuel filter. Hopefully things will get better from here. On the ride home, throttle seemed more responsive...but maybe it was just me. They showed me the PCV valve and it was just totally f'd up. I think that might have played a part in the problem...we shall see.

[Bliggida]

If the PCV valve doesn't rattle...its bad.

How much did they charge you for all that???