Bad MPG's
Bad MPG's Alright I didn't buy my car to get great MPG's, but when I get 16.5 mpg with 70% freeway driving, I think we have an issue. I just recently SeaFoamed the car which netted me a little bit over 1mpg better. 
EDIT: mod's in sig
Anyone have any suggestions on what i should do? or what any problem it could be? Ill be changing the fuel filter, and spark plugs soon. Should i be looking for anything else.
EDIT: mod's in sig
Anyone have any suggestions on what i should do? or what any problem it could be? Ill be changing the fuel filter, and spark plugs soon. Should i be looking for anything else.
Last edited by WS6_Suicide_Machine; May 28, 2008 at 11:51 AM.
TECH Resident
Joined: Aug 2005
Posts: 821
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From: SW Florida
What kind of car is it, I see a Impala in your sig, but it says ^^not my car^^..
Also, if it is an F-body, is it an A4 or M6?
Ho many miles on the car? Plugs and wires would be good like you said you are already going to be doing. Simple things like making sure the air filter is clean, you are using the correct fuel (91+ octane), Tire Pressure (I find 35-37Psi results in better mileage than say 30-32psi) etc.. will all be things to consider as well.
If you have covered all of that I guess I am not sure where else to look, and will have to wait for someone else to chime in here.
But it would be good to know what kind of car you have as well.
Also, if it is an F-body, is it an A4 or M6?
Ho many miles on the car? Plugs and wires would be good like you said you are already going to be doing. Simple things like making sure the air filter is clean, you are using the correct fuel (91+ octane), Tire Pressure (I find 35-37Psi results in better mileage than say 30-32psi) etc.. will all be things to consider as well.
If you have covered all of that I guess I am not sure where else to look, and will have to wait for someone else to chime in here.
But it would be good to know what kind of car you have as well.
Launching!
Joined: Apr 2008
Posts: 201
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Driving habits can have a lot to do with fuel economy too. I can get 180KM to a tank of fuel with my LT1, or I can get 325KM depending on how I drive. keep your foot at ease when accelerating, shift at lower RPM's and just don't drive the s**t out of it, and you'll see mileage gains.
TECH Resident
Joined: Aug 2005
Posts: 821
Likes: 0
From: SW Florida
Well I am not sure about the Impala's LT1, but for us F-body guys we are supposed to use 91+ octane fuel, and I would assume the same for your car. The fact that you are using 87 will hurt mileage too, so in the end saving 20cents a gallon by using the cheap gas isn't really saving anything, as with 91+ octane fuel you will see better milleage.
Back when I had my first LT1 in Highschool I tried using regular 87 gas several times, and my mileage dropped at least 3mpg, then when going back to using the right fuel my mileage went back to where it was supposed to be.
Also, gasoline brand makes a difference! I have testing with different brand Gasolines, and the biggest difference I have seen was when for about 3 months straight I used to use Walmarts gas at their Murphy stations 92 octane. NEVER was able to get over 23-24mpg no matter what I did on the highway. I decided to try a different brand and started filling at Sinclair 92 octane. First Tank on a highway trip I got 29mpg, and averaged 27-29mpg on all other highway trips from there on out. Because of that, I have NEVER put Murphy fuel in my car ever again.
Back when I had my first LT1 in Highschool I tried using regular 87 gas several times, and my mileage dropped at least 3mpg, then when going back to using the right fuel my mileage went back to where it was supposed to be.
Also, gasoline brand makes a difference! I have testing with different brand Gasolines, and the biggest difference I have seen was when for about 3 months straight I used to use Walmarts gas at their Murphy stations 92 octane. NEVER was able to get over 23-24mpg no matter what I did on the highway. I decided to try a different brand and started filling at Sinclair 92 octane. First Tank on a highway trip I got 29mpg, and averaged 27-29mpg on all other highway trips from there on out. Because of that, I have NEVER put Murphy fuel in my car ever again.
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well after the change out of the plugs, i noticed a difference. Soon ill be doing a CAI, new o2 sensors, and clean the MAF.
gonna try do a full comparison on 91+ next time. see what happens, because from what ive been told impalas/9c1 caprices only need 87+
gonna try do a full comparison on 91+ next time. see what happens, because from what ive been told impalas/9c1 caprices only need 87+
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I was going to suggest new O2s as well. I remember seeing somewhere that certain brands of gasoline make slightly more power than others on the dyno and by the same token would get better mileage. I believe Shell Mobile and Sunoco were among the best which is why I use only Sunoco here (also the cheapest locally).
Well I am not sure about the Impala's LT1, but for us F-body guys we are supposed to use 91+ octane fuel, and I would assume the same for your car. The fact that you are using 87 will hurt mileage too, so in the end saving 20cents a gallon by using the cheap gas isn't really saving anything, as with 91+ octane fuel you will see better milleage.
Back when I had my first LT1 in Highschool I tried using regular 87 gas several times, and my mileage dropped at least 3mpg, then when going back to using the right fuel my mileage went back to where it was supposed to be.
Also, gasoline brand makes a difference! I have testing with different brand Gasolines, and the biggest difference I have seen was when for about 3 months straight I used to use Walmarts gas at their Murphy stations 92 octane. NEVER was able to get over 23-24mpg no matter what I did on the highway. I decided to try a different brand and started filling at Sinclair 92 octane. First Tank on a highway trip I got 29mpg, and averaged 27-29mpg on all other highway trips from there on out. Because of that, I have NEVER put Murphy fuel in my car ever again.
Back when I had my first LT1 in Highschool I tried using regular 87 gas several times, and my mileage dropped at least 3mpg, then when going back to using the right fuel my mileage went back to where it was supposed to be.
Also, gasoline brand makes a difference! I have testing with different brand Gasolines, and the biggest difference I have seen was when for about 3 months straight I used to use Walmarts gas at their Murphy stations 92 octane. NEVER was able to get over 23-24mpg no matter what I did on the highway. I decided to try a different brand and started filling at Sinclair 92 octane. First Tank on a highway trip I got 29mpg, and averaged 27-29mpg on all other highway trips from there on out. Because of that, I have NEVER put Murphy fuel in my car ever again.
TECH Senior Member
iTrader: (3)
Joined: Oct 2006
Posts: 7,564
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From: Decatur, TN (N-W of Athens)
Is it just me, or does his Dyno numbers (unless those aren't his too) seem WAYYY too low for a LT1? Baby LT1 on accident maybe? :S
I run 87, but I love to drive fas :\ So I can't input my mpg.
Be crazy, mod in an M6 with 3.42s and you'll get really good gas mileage! If you live outside of Ethenol mixed gas (not E85, but Midwest states have 10% mixed at normal pump) you'll get great gas mileage. Buddy in his vette (much lighter, I know) got 32mpg highway coming back from Oregon (to Minnesota).
I run 87, but I love to drive fas :\ So I can't input my mpg.
Be crazy, mod in an M6 with 3.42s and you'll get really good gas mileage! If you live outside of Ethenol mixed gas (not E85, but Midwest states have 10% mixed at normal pump) you'll get great gas mileage. Buddy in his vette (much lighter, I know) got 32mpg highway coming back from Oregon (to Minnesota).
TECH Fanatic
Joined: Jan 2007
Posts: 1,029
Likes: 0
From: LITH, IL.
my LT1 Caprice (also a '95) would run around 18 in town and 23 highway. It has 100K MORE miles than your Impala. Your power is about right, stock ones run about 215, but your torque is waaaay low. Should be seeing around 290 lb-ft at the wheels. I had trouble with the passenger side cat clogging and knocking my mileage down before it totally locked up on me (in hindsight, probably took 10K miles). Also, my Caprice is running 3.73 gears (vs your 3.08) and a 2800 stall. You have a mechanical problem someplace. I would check your exhaust first.
Also, the iron headed LT1's all had the 191/196 111 cam and are designed to run on 87 Octane.
There is exactly zero chemical energy differences between the different Octane fuels. No difference in flame propogation speed, Only think different is the higher Octane will take a higher temp to light off. If anyone was getting worse or better mileage, and was not having timing pulled due to knock, it had nothing to do with the rating of the fuel.
Also, the iron headed LT1's all had the 191/196 111 cam and are designed to run on 87 Octane.
There is exactly zero chemical energy differences between the different Octane fuels. No difference in flame propogation speed, Only think different is the higher Octane will take a higher temp to light off. If anyone was getting worse or better mileage, and was not having timing pulled due to knock, it had nothing to do with the rating of the fuel.
Definately switch to 91+ octane. I run 93 all the time. But, last week I decided to try 89 (10% ethanol). Usually I get somewhere around 175 miles, when the gauge is at half, with a heavy foot, on 93. With 89, my gauge was at half, with just 125 miles. And that was fairly easy driving. Not to mention, it was running like crap with the 89. I've never really factored up my MPG, so I don't know the difference. But, it seems like quite a bit. Plus, I can't really factor it up, by just saying half. Because the first half always seems to go alot quicker than the 2nd. The damn gauge is never right.
my LT1 Caprice (also a '95) would run around 18 in town and 23 highway. It has 100K MORE miles than your Impala. Your power is about right, stock ones run about 215, but your torque is waaaay low. Should be seeing around 290 lb-ft at the wheels. I had trouble with the passenger side cat clogging and knocking my mileage down before it totally locked up on me (in hindsight, probably took 10K miles). Also, my Caprice is running 3.73 gears (vs your 3.08) and a 2800 stall. You have a mechanical problem someplace. I would check your exhaust first.
Also, the iron headed LT1's all had the 191/196 111 cam and are designed to run on 87 Octane.
There is exactly zero chemical energy differences between the different Octane fuels. No difference in flame propogation speed, Only think different is the higher Octane will take a higher temp to light off. If anyone was getting worse or better mileage, and was not having timing pulled due to knock, it had nothing to do with the rating of the fuel.
Also, the iron headed LT1's all had the 191/196 111 cam and are designed to run on 87 Octane.
There is exactly zero chemical energy differences between the different Octane fuels. No difference in flame propogation speed, Only think different is the higher Octane will take a higher temp to light off. If anyone was getting worse or better mileage, and was not having timing pulled due to knock, it had nothing to do with the rating of the fuel.
when do you need to go toemissions again? why not just delet your cats? but if you insist on getiing cat I like my magnaflo cat but I also have a 95 z28 so fitmit may be different.
TECH Fanatic
Joined: Jan 2007
Posts: 1,029
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From: LITH, IL.
A shame too, just replaced the original tranny with a pretty stout one about 3K miles before it died. Tires/brakes under 2K miles, etc. Hard to justify spending the coin to replace the engine and having twice in the car than it would be worth...
Again to those throwing in their 2 cents about running the higher Octane; The Fe head LT1's DON'T need it with the stock cam and programming!!!
