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post #1 of (permalink) Old 01-14-2017, 04:07 AM Thread Starter
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Low Gas Mileage?

I'm trying to figure out whether or not I'm getting rather low mileage for my car, as it's rated 19 city - 29 highway or somewhere in that range, and I've been getting somewhere between 21.9-22.9 mpg driving to work each day.

For comparison, I drove to Philly last month and got over 25 mpg.

Is this to be expected with my car or is there something I can do to increase the mileage? I drove a similar size car earlier last year (a Dodge Intrepid) and I was averaging 24 with no change in my route to work. For most of the trip I drive down a local state route and I'm on the interstate for about 12 miles, for a total of 24 miles altogether. It just seems to me that I should be getting more miles out of my gasoline.

I've been told to try Seafoam, but is there anything else anyone can recommend, or warn against doing? I'd like to cover all bases.

2003 Chevrolet Impala Base
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post #2 of (permalink) Old 01-14-2017, 05:17 AM
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Check your tire pressure. I run 37 psi instead of the recommended 32 and saw a decent bump in mileage.


~Joe~

04 Impala LS

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post #3 of (permalink) Old 01-14-2017, 09:34 AM
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Correct tire pressure is excellent advice.

Does your heater warm-up quickly? If not, it is possible the thermostat is stuck open. This will set a code but will not illuminate the check engine light. An engine with a stuck-open thermostat will have less fuel mileage than an engine with a good thermostat.

You live a cold weather area. I do too and have found that the winter blend gasolines provide less mileage. If you are buying gas with 10% or 15% ethanol content, that type of fuel will also lower your mileage. In the area I live, it is almost impossible to find gasoline that does not have ethanol added.
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post #4 of (permalink) Old 01-14-2017, 09:42 AM
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when's the last time you changed your fuel filter? your signature shows an 03 impala, that's why i ask. also how much stop and go is in that drive to work? i know mine in heavy stop and go gets 14-16 city right now because of winter gas. in the summer it's up to 18 consistantly. now i do have a remote starter on it so that accounts for a bit of the drop. just some thoughts. throw a gas treatment down a full tank and see if it gets any better. would be a cheap fix if it does.
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post #5 of (permalink) Old 01-14-2017, 02:08 PM Thread Starter
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Quote:
Originally Posted by 04Imp38 View Post
Check your tire pressure. I run 37 psi instead of the recommended 32 and saw a decent bump in mileage.
All my tires have 30 psi and have had that since November when I bought the car. Also I don't want to overinflate but I'd be happy to look into increasing the tire pressure a bit.

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Originally Posted by 1999 White C5 Coupe View Post
Correct tire pressure is excellent advice.

Does your heater warm-up quickly? If not, it is possible the thermostat is stuck open. This will set a code but will not illuminate the check engine light. An engine with a stuck-open thermostat will have less fuel mileage than an engine with a good thermostat.

You live a cold weather area. I do too and have found that the winter blend gasolines provide less mileage. If you are buying gas with 10% or 15% ethanol content, that type of fuel will also lower your mileage. In the area I live, it is almost impossible to find gasoline that does not have ethanol added.
I'll have to time my heater when I drive my car today, I don't seem to have a problem with it when the engine warms up though.

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Originally Posted by Joes74challenger View Post
when's the last time you changed your fuel filter? your signature shows an 03 impala, that's why i ask. also how much stop and go is in that drive to work? i know mine in heavy stop and go gets 14-16 city right now because of winter gas. in the summer it's up to 18 consistently. now i do have a remote starter on it so that accounts for a bit of the drop. just some thoughts. throw a gas treatment down a full tank and see if it gets any better. would be a cheap fix if it does.
I've never changed my fuel filter nor would I know how much work it would take to get done, but if it's something where the whole tank needs to be dropped...

As for stop and go, not so much. I go through two lights in the first two miles, then two more when I get off the interstate, then the gate at work, so I don't stop all that much. I don't have to go through big city traffic, thank goodness for that.

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post #6 of (permalink) Old 01-14-2017, 02:44 PM
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Quote:
Originally Posted by hg3300 View Post
All my tires have 30 psi and have had that since November when I bought the car. Also I don't want to overinflate but I'd be happy to look into increasing the tire pressure a bit.



I'll have to time my heater when I drive my car today, I don't seem to have a problem with it when the engine warms up though.



I've never changed my fuel filter nor would I know how much work it would take to get done, but if it's something where the whole tank needs to be dropped...

As for stop and go, not so much. I go through two lights in the first two miles, then two more when I get off the interstate, then the gate at work, so I don't stop all that much. I don't have to go through big city traffic, thank goodness for that.

Your vehicle has an external, in-line fuel filter. It is on the left (driver's) side of the car, underneath the floor pan below the rear seat area. It is easy to change IF you have the correct tools. A partially clogged fuel filter should not cause poor mileage, but could causes "surging" on moderate or heavy acceleration.

I would check the tire inflation label on the LF door jamb - it will tell you the cold (not driven) tire inflation PSI. I suspect your model has a 32 - 34 PSI recommendation. A good rule of thumb is that the tire PSI drops 1 PSI for every 10 degree drop in ambient temperature. It also increases 1 PSI for a 10 degree increase in the ambient temperature.

Under inflated tires can cause a drop in fuel mileage. I would check them and inflate to the recommended PSI.

I would also check your air filter and change it if it is dirty. Good luck.
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post #7 of (permalink) Old 01-14-2017, 03:14 PM
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Quote:
Originally Posted by hg3300 View Post
All my tires have 30 psi and have had that since November when I bought the car. Also I don't want to overinflate but I'd be happy to look into increasing the tire pressure a bit.
Good deal. IIRC the max tire pressure on my tires is 40 psi and 60 to seat the beads, so yours is most likely the same. I run 37 psi in the summer (haven't checked it in the winter so it's probably down a little) with no issues. The tire pressure light will come on if it is overinflated as well as underinflated (don't ask how I know)


~Joe~

04 Impala LS

LED cluster, HVAC, headlights, interior lights
Dual Stainless Xlerators
Stainless Xlerator Resonator
4 inch Stainless Tips
ZZP DP
ZZP PCM
ZZP 180 drilled t-stat
Optima Red Top battery
Tubular trailing arms
Police LCA's
Police brakes
Dorman solid sway bar
Many more mods to come!
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post #8 of (permalink) Old 01-16-2017, 03:46 AM Thread Starter
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Quote:
Originally Posted by 04Imp38 View Post
Good deal. IIRC the max tire pressure on my tires is 40 psi and 60 to seat the beads, so yours is most likely the same. I run 37 psi in the summer (haven't checked it in the winter so it's probably down a little) with no issues. The tire pressure light will come on if it is overinflated as well as underinflated (don't ask how I know)
Considering my radio won't enter the customization menu and I never got a 'change oil' message (or whatever is supposed to come up for that?) I wouldn't be surprised if I don't get a tire pressure message either.

I want to fix the problem but it seems like to do so I might need a whole new OEM radio and have it programmed to the VIN.

Anyway, back on topic, my car heats up in about 3 minutes and reaches the average operating temp in about 6 (which is currently just under 185 degrees) so from what I've been reading my thermostat is working properly?

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post #9 of (permalink) Old 01-16-2017, 04:02 AM
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Yep. Sounds like the thermostat is doing its job.


~Joe~

04 Impala LS

LED cluster, HVAC, headlights, interior lights
Dual Stainless Xlerators
Stainless Xlerator Resonator
4 inch Stainless Tips
ZZP DP
ZZP PCM
ZZP 180 drilled t-stat
Optima Red Top battery
Tubular trailing arms
Police LCA's
Police brakes
Dorman solid sway bar
Many more mods to come!
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post #10 of (permalink) Old 02-19-2017, 11:45 AM Thread Starter
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Quote:
Originally Posted by 1999 White C5 Coupe View Post
Your vehicle has an external, in-line fuel filter. It is on the left (driver's) side of the car, underneath the floor pan below the rear seat area. It is easy to change IF you have the correct tools. A partially clogged fuel filter should not cause poor mileage, but could causes "surging" on moderate or heavy acceleration.

I would check the tire inflation label on the LF door jamb - it will tell you the cold (not driven) tire inflation PSI. I suspect your model has a 32 - 34 PSI recommendation. A good rule of thumb is that the tire PSI drops 1 PSI for every 10 degree drop in ambient temperature. It also increases 1 PSI for a 10 degree increase in the ambient temperature.

Under inflated tires can cause a drop in fuel mileage. I would check them and inflate to the recommended PSI.

I would also check your air filter and change it if it is dirty. Good luck.
Tire PSI sticker is under the trunk lid. I did notice my left side tires were both around 30 so I increased them to 32 to match the right. Also filled my spare tire to 60, it's probably been low since I bought the car.

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post #11 of (permalink) Old 02-22-2017, 03:38 PM
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I have an 05 impala 3.8l. It was getting about 24-25 mpg. Well when I got cold out 15 to -15 the throttle would stick every now and then. Long story short the throttle body was full of crap. A can of throttle body cleaner and some mass air flow cleaner. With a little bit of time. Along with taking things apart. It started to get 27-28 mpg.
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