I made a 2500 mile test run for mileage (Road trip) and got some interesting info. I recorded altitude, temps and got some interesting info. Altitude was recorded with my altimeter which is accurate to with in one foot and reacts almost immediatly.
I averaged 70 miles per hour for the whole trip including stops for gas, food, traffic jams and to do the job in Arizona. On the way out there I ran 75+ most all the way, left at 2:45 in the morning and was there by 8:00 at night mountain standard time. Stopping only for gas and restroom breaks.
I averaged 28.7 MPG on the return trip 1250 miles. I had to kick it down hard many times in the mountains and to pass but for the most part I kept it on cruise control to check mileage. I was not able to get much info on 60 and 65 MPH because I ran the speed limit or 5 mph faster most all of the trip. On the times I was doing 65 or less there was usually traffic etc. It was cool so I did not have to run the Air conditioner much the whole trip surely that saved me some.
60 approx 39.
70 MPH averaged 35 MPG.
75 averaged 30.8
80 averaged 28.4
The altitude started at 660 feet and went up to over 4500 feet and back down to 304 at my destination. Then did the job and drove back home back over the mountains.
It was very windy most of the trip both ways and most of it was a headwind.
The car performed like a champ, it was comfortable enough that I was able to basically go 1250 miles stopping only for gas. The car handled great in the high winds and that is because of the lowering springs. It did not handle NEARLY as good with stock springs in high winds.
I do not reccomend driving 2500 miles in 2 days with little sleep but the desert was beautiful and I got the job done and got home. The car was the least fo my worries. Poor little car is very dirty now and one small bird decided to commit suicide on the front of my car. The car did well, the bird,... not so much.

Glad You Had A Safe Trip ! The Sweet Spot For Best Gas Mileage On My Ss Is Around 63-65 Mph. I Average Mid To Hi 30's With That.

I read a book about '55-'57 Chevrolets. Motor Trend Magazine tested a '55 having a 265 V8 with 180 hp, and weight of 3100 lbs. Similar to an HHR. They got 16 mpg at 60 nph, and 14 mpg at 75 mph.

I would rather have an HHR instead of a '55.

Well, the 55-57 has all of the aerodynamics of a brick. Plus the drivetrain is much more effecient now than they were back then. With one of these little 2.2 or 2.4 motors in them they would be much better on fuel effeciency but still not as good as we are getting due to aerodynamics.
Also the 55 did not have air conditioning, electric windows, good radio, comfortable interior and it was not nearly as nice and quiet of a ride. We have come a long way in only 53 years.
We also had to change points, plugs, plug wires and oil every 3000 miles. Now we just drive them.

lol, so you just decided to drive to arizona just to check your MPG average? wish i had that much extra time on my hands....but glad to hear you had fun....take any pics?

lol, so you just decided to drive to arizona just to check your MPG average? wish i had that much extra time on my hands....but glad to hear you had fun....take any pics?

lol no andrew.. he said.. "to do the job in Arizona" ..
meaning he went there to work on something. :p:

2500 miles in 56 hours with 10 hours sleep total during that time was not fun. I had a problem with one of my compressors and had to fix it. I got the call Tuesday afternoon and Wed morning at 2:45 I was on the highway Friday morning I was back home. Then I had a bunch of catch up work to do when I got home so it has been a little hectic. The whole trip only cost about $160 in gas and that was pretty cool, the last time I went to Las Vegas in my dually truck (about same distance) I spent about $1500 in gas. Curly

2500 miles in 56 hours with 10 hours sleep total during that time was not fun. I had a problem with one of my compressors and had to fix it. I got the call Tuesday afternoon and Wed morning at 2:45 I was on the highway Friday morning I was back home. Then I had a bunch of catch up work to do when I got home so it has been a little hectic. The whole trip only cost about $160 in gas and that was pretty cool, the last time I went to Las Vegas in my dually truck (about same distance) I spent about $1500 in gas. Curly

thats a hectic few days for sure. but atleast u save 1300$ n gas :lol:

Guys,

We drove to my Mom's in central Florida this Christmas. It all begins at 12 midnight and we drive 14+ hours until we get there. The car had 2700 miles on it when we left and the only mod is a radar detector and a Mobil 1 oil change.
On an earlier trip when the car was new we got 26-34.7 mpg. This trip we got 24-26 mpg which is different I think. I tried to think of what it was that was done differently but except for more luggage and cargo, we drove the same route 95 at 70-85 mph. The temperatures were colder and the wind was stronger.

I have noticed that our city mileage varies quite a bit as well. It has been as good as 25 city or can be barely over 20 MPG.

This is neither good or bad it is just that it is variable by quite a bit. I wonder how in the world we ever got 34.7 MPG; I remember us driving less than economically on that tank?

QuickRick

My mileage is all over the place and I do not know why. I might get 35 MPG and then in similar conditions later same speeds get 29????
Until I get some sort of consistant results all are suspect. If you find out why your mileage dropped from 34.7 to 26 let me know.

Curly,

I will bet good money that 10% ethenol or not in the fuel is part of the reason. You will note that the tag on the pump states that it "MAY" contain 10% (or it may not!)

I also think that the car isn't all that aerodynamic so there is probabaly a huge diff in MPG vs road speeds. Now that we have been in town doing errands and such in mixed driving, I am getting more MPG in city /urban driving than we got on the highway....it's odd.

I too would love an explanation.

QuickRick

Ethanol certainly may be part of the reason. Sounds like a good topic for a new thread.
Why is the mileage worse in cold weather? Why is there no consistancy? Weather? Ethanol? A car performs better and makes more horsepower in cold weather so you would think it would get better mileage (have to use less throttle)
How much Ethanol is in the gas we use and how much does it hurt mileage?
What is the mileage difference in Winter and Summer blend gas?

Still my car can get different results on the same tank of gas?

We do not have any snow here in the United States of Texas but we have got some temps in the teens and twenties.

I am looking for some consistancy or I can never know for sure if my changes are improvements or not.

For instance I do not pay much attention to city mileage because there is too many variables. But my average mileage started at about 21 for a tank, then went to 23 with some of the mods and with exhaust it went to 25 MPG.
So in the last 9 months my city average went up 4 MPG and that is significant. Last tank went to 19 MPG and I do not have a clue why? I was thinking my mods were working and the BAM! I get 19 and do not know why. That was not a full tank and it is climbing.
I expect (Hope) that with the Trifecta tune and underdrive pulleys it will gain a little more.
The EPA ratings was 21/30 and that was very close to what I was getting when I got the car. Now I am about 25/35 and hope to end up with it about 28/40 when all of the mods are done.
I think that would probably be around the max for mechanical mods with out going to adding ugly aero tails on the back, wheel well covers or other hideous looking aeromods.

From there I can start doing some Hypermiling techniques and possibly improve the overall even more. Right now I am working on mechanical mods and for the most part it seems to be working but not as consistant as I think it should be.

Its possible you have other issues at hand.Maybe you have a sensor thats operating on the fringes,not enuf to kick off a light but enuf to vari the parameters.O2 sensors can do this.A vacuum leak can play games too,at certain temps may work good and others cause it to leak.Stupid things like voltage swings, you do have a lot of stereo .. coil output is dependant on voltage..(I wonder how these would run on a step up box,say 16v?)If this is something thats ALWAYS been happening then I'd look at everything.Otherwise if this started after a particular mod,backtrack and troubleshoot that mod.You said you changed tire size,was it recal'd after?The ECM may be trying to compensate and confusing itself. Its like a puter,go back to the last known stable state and work from there.

I just filled up and got the final mileage on that tank of gas. I had been getting 24 tp 26 in the city and this one was 21. It has been windy and cooler lately but 21 is not very good.