need help getting 12.7 miles per gallon

flowmaster02 said:
03 and up are gen2 same size engine but more power do to changes in the engine but I don't think they get that good of gas mileage on the street through. Next I'm gong to clean the Mass Air Flow Sensor and hopefully that will help out some too. Thinking about getting rid of my 20s and getting 17s to drop some weight. I'm trying to do anything I can to get better gas mileage. I don't want to get rid of my car but if I have to I will.
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Maybe I forgot, but how much city/highway driving to you do? Be liberal with the use of the cleaner, but make sure it's plenty dry before you reinstall it.
 
Good to hear that your brother is coming home. I mostly do city driving, I'm only a couple of miles away from work and friends.
 
flowmaster02 said:
Good to hear that your brother is coming home. I mostly do city driving, I'm only a couple of miles away from work and friends.
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What do you get when you do highway driving?

How long have you owned the car and how long have you been getting terrible fuel economy?

Does your car reach full operating temperature when you drive it? If not, how often does it reach full operating temp for longer than 10 minutes?
 
I'm not to sure with the highway mileage haven't been on a long drive on the freeway for a while but I think the last time I checked it was about 18mpg. I've had the car for about 3.5 years and been getting bad gas mileage for about a year give or take. The temp gage only goes half way but thats normal.
 
What I'm getting at is if you drive only city and very short distances you could be getting a carbon buildup in the engine, which could also be plugging up the cats. If this was my car I'd pull at least one of the spark plugs and look at it for buildup. I'd also get a flashlight so I could look down into the cylinder to see if there's a carbon buildup. If there is then a upper engine cleaner would be a good idea. A good one is supposed to be G2P(guaranteed to pass). I've heard good things about this product and GMs Top Engine Cleaner and Seafoam. This is just a suggestion. A real oldschool method of removing carbon from the engine is water or steam injection. This method is probably bad for your o2 sensors, but the others might be bad too.

Out of curiousity, what city fuel economy did you get before? 18MPG on the HWY is bad for any LS.

I also have good news, I've just got news that my brother will be coming from early from Afghanistan about the second week of June so if I go down south it will be sooner rather than later.
 
flowmaster02 said:
If I were to switch my mufflers from flowmaster to magnaflow would that give me better gas mileage?
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Maybe, but it wouldn't fix your bad fuel economy problem. I doubt that the cost of the mufflers would pay for themselves unless you have mufflers that are plugging up somehow. What kind of fuel economy are you getting right now? Did you try any of the tricks I suggested?

On a side note my brother already came back from afghanistan but we ended up turning right back around and came back up north within hours of him arriving. Sorry
 
flowmaster02 said:
I changed the plugs and ignition coils last year around june. But it hasn't but running funny or anything just crappy gas mileage.

I've had the car for about 3.5 years and been getting bad gas mileage for about a year give or take.
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What brand of plugs and coils did you put in? Did you set the gap on the plugs yourself? Seems like that's when your mileage went down...
 
mechanicboy: I'm getting around 14.4 average now(90% of my driving is street driving compared to freeway) and the mufflers shouldn't be clogged on have had them a couple of years. The only reason I asked is because I heard that magnaflow has a strait shot out compared to the flowmasters. LDM: I'm not sure its been awhile since I had them changed but I got the coils off of ebay (I was broke at the time) and the plugs I got from Kragen but my mechanic said he would gap the plugs properly.
 
Make sure you are using your I do believe 91+ Octane Fuel. Stay out of the floor on it.
Usually City driving I can get average 17 to 18 when I Granny Mode it. But With the new Exhaust I get about 13 to 14 now xD Since I love the sound lol. But highway I can get 20-24 , 24 If Im really drivin the car right and get it in its sweet spots and do some Prius Driving.

Make sure your using right fuel, Clean out your Throttle Plates, MAF, change your Spark Plugs, and possibly even wiring.

All in all, I would recommend stopping by Pep Boys or what have you and get a complete Tune-Up, New Plugs Wires and ect.. Would be cheaper and less of a PITA then doing all yourself. Thats just me though..

And if non of these help yeah. THEN move on to the Bigger Issues such as Cats and what have you. :)

But this is all just my opinion. And after you get your Tune-Up, You know that its been Recently done and have it all on paper so no money spent Wisely. Both in attempting to fix a problem and keeping up with the Maintenance
 
How would I clean out my throttle plates? I alread did the MAF Spark plugs are only about two years old now.
 
Get some Carb Cleaner. Take off Plastic Intake. And with spray some carb cleaner on the Throttle body plates. and maybe use a tooth brush to get some gunk off if there is any. When you go to start your car keep in mind might be a little hard to start due to the Carb Cleaner.. But should turn over after a little
 
when i first got my car, about two months ago, i was getting about 17.3 mpg city/country driving. now since then ive put in new plugs/COPs, heat shield, cleaned o2 sensors and seafoamed and now im getting 19.5 mpg. just my .02. also drove like a granny haha
 
There's only one throttle plate and you'd notice other drivability problems if that was you problem. There's no spark plug wires on the ls. Flowmaster, yes a magnaflow exhaust would flow better but I don't think you will see a return on you investment anytime soon. Have you used any of cleaners like I suggested previously?
 
So I finally took out my ls for a good drive on the freeway and got alright gas mileage. Before I left I reset the mpg reader and I was getting just over 24 mpg on the freeway with no traffic. When I got home after city driving and all that it was at 19.4 or something like that. M boy I have put in the seafoam and another oil additive can't remember the name right now but hasn't really done much. If I were to switch out my o2 sensor would that help?
 
flowmaster02 said:
So I finally took out my ls for a good drive on the freeway and got alright gas mileage. Before I left I reset the mpg reader and I was getting just over 24 mpg on the freeway with no traffic. When I got home after city driving and all that it was at 19.4 or something like that. M boy I have put in the seafoam and another oil additive can't remember the name right now but hasn't really done much. If I were to switch out my o2 sensor would that help?
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That would be about right, especially if you're running the a/c. Ethanol "enhanced" fuel will also give you fewer miles per. Remember, ethanol has ~10% less energy than gasoline.
 
15 Mpg is my average but I really dint go by the computer unless you reset it ag every fill up and drive only local.
 
Just a heads up, after swapping my upstream O2 sensors, I noticed no difference in mileage. Driver-side sensor was causing a CEL.

Your mileage sounds about right. Like LS4me suggested, is the gasoline you use Ethanol-free?

Also, take note of miles/km traveled between fillups and amount of gas added, and manually calculate your MPGs for more accuracy.
 
Next time I fill up i'll do it manually and see if the computer is off. I'm not sure if the gas is ethanol-free or not. Does 76 use that stuff?
 
flowmaster02 said:
Next time I fill up i'll do it manually and see if the computer is off. I'm not sure if the gas is ethanol-free or not. Does 76 use that stuff?
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If the station doesn't have easy to see signs saying that it is ethanol free, then it very probably isn't.
 
flowmaster02 said:
So I finally took out my ls for a good drive on the freeway and got alright gas mileage. Before I left I reset the mpg reader and I was getting just over 24 mpg on the freeway with no traffic. When I got home after city driving and all that it was at 19.4 or something like that. M boy I have put in the seafoam and another oil additive can't remember the name right now but hasn't really done much. If I were to switch out my o2 sensor would that help?
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About 24-25 is about right for HWY MPG. I would say it's not plugged cats because you would likely have observed lower MPG than that.

The others are right on hear about the ethanol. Unfortunately ethanol free gas is about non-existent in CA. I believe that ethanol is less efficient than gasoline fr more than 10%, I believe it to be closer to 25% less fuel efficient. Another problem california drivers have been facing is even though the sticker on most pumps say up to 10% ethanol may be contained in the fuel independent tests have shown up to 20% ethanol at those pumps. Your only alternative is to try different brands of gasoline for several tanks with the same driving habits and see if the MPG gets better on one or another. It's really hit and miss and I can't really suggest any good gas just stay away from off brands.

Changing your front O2 sensors(since there's two of the fronts and two in the rear, the fronts being the important ones) may or may not help your MPG. I replaced mine thinking it was causing a fuel problem and was completely wrong and basically wasted my money. I do have piece of mind knowing that they were good though as my MPG didn't change noticeably after replacing my front O2 sensors. If for some reason you believe yours are actually bad and want to replace them just for giggles I'd sell you my old ones for say, $20 shipped(pending shipping price is cheap) for the pair of old ones I pulled out I know worked. I'll guarantee them against DOA in case something happens and I'll refund your money no questions asked(even shipping).

I can't remember if you did this or not but have you cleaned your MAF sensor? And we ruler out a high idle right?
 
One thing to keep in mind is that the computer MPG is more accurate with the more miles you drive since reset. Certain things like sitting at long lights or a fast food drive thru kills the computer MPG. The computer averages the total consumption and doesnt necessarily reflect the actual driving MPG. You can be getting 24 highway and 18 city MPG, which is normal... but the more traffic or stop lights or idleing you do lowers the average quickly.
 
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