I heard a similar incident when someone put regular in instead of premium, and his mileage went way up. It turned out he was afraid to nail it and get ping, that he was easy on the throttle, which gave him the better gas mileage.

It may be unconscious that you're driving a little more aggressive now.

 

That's not surprising for a manual transmission car. Few drivers can hit ideal shift points every time. The auto always does. So auto city mileage will almost always be better than for a manual. Example, I get 22-23 MPG in my automatic C6 around town. Your highway mileage really sucks, though. You should be getting 28-29 MPG regularly on the highway. That's what I get with my auto, and you should have slightly less driveline loss with the manual.

 

22 to 23 mpg city was norm for about 2 years till I changed the exhurst system. Now that said. I do not drive it daily. once a week at most on weekends and the first trip over 2oo miles was last week. The City,, north of Dallas. So all of you around the metroplex know my driving has been cut to maybe once a month.... due to all the rain. I am not complaining about the mpg. I am just stating fact. it dropped.. I will give you that it does sound sweet and maybe I do get on it a little more know, but for it to drop that much my right foot would have to be in the fire wall all the time and it is not. The Hwy mpg before was 25 to 26. The reason I beleive it is lower then the 28, 29 and 30 I see on here all the time is because of the Dif. being a 3.15 and not a 2.73 that most 05s have.

As I said I was just wondering why it drop. The last time I got on it. It jumped in and out of the passing gear two or three time real quickly.. Making me beleive that maybe a plug wire or something like that is loose or cut cause it to jump.

 

Look ... here's a few things to consider:

1. The mpg calculation is an average. If you have gone very few miles and you get on it, the mpg will drop down very low. Same thing will happen if you sit at a traffic light or stop sign. When idling, for all the minutes at the light, your mpg is zero. Average that in with your highway driving and you can easily see why your average should be <20mpg
2. Averaging 17-20 avg mpg should be considered GOOD mileage if you average in a little bit of hard running, city/suburban driving and highway driving. Yes ... there are guys claiming to get 23, 25, etc. mpg+ over long periods of time. Well, guys getting that mileage must be spending the vast majority of their time cruising at even highway speeds in flat territory to achieve that result. They also have to live pretty close to a 55 mph zone so they don't have to idle too much or accelerate from stop signs or traffic lights on the way to the highway. Lastly, they have to drive with a very light touch on the pedal.

As some of the other forum members said ... you have more variability in your right foot than you do in the hardware mods you made. One last thing, automakers are notorious for optimizing the test conditions so the published mpg ratings can be as high as possible. It would be foolish to think the average car of the production line with an average drive in real world conditions will even achieve those ratings on a consistent basis. ... jmho

 

I am neither surprised nor disappointed by my mileage. I might see 28-29 mpg at some points if I just happen to be on a dead flat section of road cruising at 60 mpg. Frankly, I don't care about the mpg anyway. If I was driving a Civic, it might be an interesting project to see how high I could get the mpg. In the Corvette .... why bother. I drive only a few 1000 mi per year in the car and the cost of the extra gas is really meaningless.

 

Thanks Mitch.

Just seems a little low since I don't really get on it much. I'll recheck when I take it out and reset again.

 

The roads here in the foothills of the Appalachians are anything but flat, and I certainly don't poke along at 60 MPH when driving them. But I still average 28-29 MPG. 22 MPG is really bad for highway mileage in this car. It should get that in the city. Something is wrong, either with the car or the way it is driven, to get mileage that poor. You may not care, its your car and your money, but it would concern me. I drive my car a lot, about 1800 miles a month, so I care if it is running at peak efficiency. If my MPG was sharply lower than it should be, I'd want to know why.

 

that is the CORRECT answer if any change at all were to happen the lowering of backpressure would give you a slight increase but i have seen it many,many times throughout the years.....um take your foot out the gas !