Different States, Different Gas Milage?

I'm trying to explain to myself why my vehicle ('98 'Burb) has never gotten over 15 mpg while others report up to 20 mph. In my experience, the roof racks I
have on it are good for maybe 1 mpg - which leaves the rest in question.
Does anybody notice different MPG figures for the same temperature ranges in different states?
Somewhere I heard that different states mandate different percentages of ethanol in gas that's sold there.
I'm pretty sure that adding ethanol reduces MPG....but don't have any idea whether it's by a significant amount.
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PeteCresswell

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(PeteCresswell) wrote:

Good question. There are a lot of varibles here. Tire size, tread type(cleated tires have more rolling resistance)axle ratio and grade of gas as well as its content (gas with alchol has less heat energy in it and heat energy drives a IC engine). Modern engiens really need more than 87 octane and Detriot maintain compatabitly with 87 octane fuel by using knock detection and control to sense knock before you hear it and retarding the timing to control it and while doing so reduces engine efficency and power and MPG with it. I get a honest 17 to 18 MPG on highway regularly with my 89 4x4 burb with stock smooth tires and a 175K on it and have gotten as high as 19 at times too but I never use 87 in it as power and MPG greatly suffers when I use it.
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Per TheSnoMan:

What octane do you regularly use?
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(PeteCresswell) wrote:

I use mostly 91 or better though I used 89 sometimes in cooler months. Even in my 2000 K3500 with a Vortec 350 in it I use at least 89 all the time too and you can feel the difference driving it too.
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By using higher octane is just a bunch of B.S,unless you have a higher compression engine. I used 92 in my 97' Z71 several times,in several states,and it did nothing. I have gotten 20+ mpg on 87.
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Bill wrote:

The BS is beliving you do not need it. You do not now what your are missing until you run a few tanks of it because 87 was designed for 8 to 1 CR in the 70's and 80's not today 9 to 1 plus engine. If it was such a great gas, modern engine would not have knock sensors to control consumer complaints. Plug a realtime monitor into your OBDII port and watch the timing and see the difference between 87 and 91.
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Lots of the engines are not 9 to 1, but are designed to be run on 87 octane. except the foriegn cars. all mine run fine on 87 and the knock sensor works if they don't. Besides, the lower price offsets any little problem. old john
BUY AMERICAN or you are part of the problem.
Hello, TheSnoMan! You wrote on Tue, 10 Jan 2006 01:41:05 GMT:
T> Bill wrote: ??>> By using higher octane is just a bunch of B.S,unless you have a ??>> higher compression engine. I used 92 in my 97' Z71 several times,in ??>> several states,and it did nothing. I have gotten 20+ mpg on 87. ??>> T> The BS is beliving you do not need it. You do not now what your are T> missing until you run a few tanks of it because 87 was designed for 8 to T> 1 CR in the 70's and 80's not today 9 to 1 plus engine. If it was such a T> great gas, modern engine would not have knock sensors to control T> consumer complaints. Plug a realtime monitor into your OBDII port and T> watch the timing and see the difference between 87 and 91.
With best regards, snipped-for-privacy@comcast.net. E-mail: snipped-for-privacy@comcast.net
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snipped-for-privacy@comcast.net wrote:

Narrow thinking indeed. 20 or 30k or more car and burn the cheapest gas you can find. Thye run "fine" because you know no different and if they were designed for 87, then why does detriot use premium in all of their EPA MPG tests???? They do not tell you a lot of things about those tests. Knock sensors are for keeping people such as yourself in happy bliss with less than maximum performance. You caanot retard spark with low octane fuel without losing power plain and simple. 87 should have died with carbs and low compression.
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But to me, the real question is whether or not
((MilesDriven/MPG@87) * CostOf87)
is less than, greater than, or equal to
((MilesDriven/MPG@91) * CostOf91)
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Have a 91 S-10 that gets (at best) 20-21 mpg on Calif freeways, but last Spring I filled up with Nevada gas and made 26 mpg on that tank going down US 395...Amazing just how crappy our state has made our gas
We burn 20% more of it and the state gets 20% more in taxes..and it's suposta reduce smog? How? By using more of it? (end of rant)
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Exactly, Ken... Though we all know that driving habits and things can make a big difference, the bottom line is that the "clean burning" crap we get in Calif. is a very bad idea..
We travel from central CA to the Seattle area several times a year and the difference between our "normal" mpg and the mpg on the way home (after we've burned the CA crap out of the truck) is always over 10% higher...
They try to make it cleaner burning (and use crap that screws up the ground water) and even if it worked to clean up the air, the fact that you need more of it to drive each mile more than offsets any good from it, IMHO..
We've taken several trips up 395 to Topaz Lake and the mileage is always better on Nevada gas...
I think that they need to make it a little easier on us and the oil companies by creating some sort of national standard for at least regular unleaded, so they could sell the same stuff in each state...
mac.. who hates paying high gas prices because gas can't be shipped in from neighboring states when needed..
mac
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(PeteCresswell) wrote:

    Elevation can make a difference as well. Compare Denver to death valley, and your talking a mile difference in elevation. Cars preform better at or below sea-level.
    At drag strips a "corrected" time slip means they have adjusted for the therietical at sea-level. Charles
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Charles Bendig wrote:

Actually I have gotten some of my best MPG at altitude a few times because of reduced wind drag in thinner air. Once I got a honest 42 MPG with a 91 Camary with a 4cyl and 5peed when it was a year old on a trip thru the high plains of WY averaging 70 to 75 MPH with A/C on. At lower elevations it would do 35 to 38 most of the time.
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Hey Snoman, I have an 89 GMC with TBI 7.4, would that have the knock sensor and all that in it too? My mileage thus far hasn't been all that good, all on 87 gas, wondering if 91 is worth a shot...
BTW great thread guys, interesting just to hear some solid numbers on what people are getting, I've been trying to convince the wife to ditch her minivan for a suburban(for towing) and those numbers may just help me win ;-)
Ed
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89GMC wrote:

All GM TBI and Vortec engine have knock sensors. ALso with you 89 7.4 you can also advance the baseline timing easily when you switch to 91 to take advantage of the additional spark for power and MPG. I do run my 89350 at 6BTCD for static timing instead of TDC as specs call for and I had to run it at 2ATDC with 87 to bevent it from knocking at times with 87 when it was newer before I switched over many years ago. The TBI engine cannot vary the spark as much as the Vortec engine can to control knock so they are a bit more prone to want to knock at times. My burb runs like a completely different animal withtiming set the way it is and better gas. Even after owning it since new I am still amazed at the fuel mileage it can deliver on long highway trips today. 600 miles with some gas left over is not a problem with its 40 gallon tank.
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<snip>

I wondered about that, too, Sno.... maybe EFI compensates better than a carb does?
Some of our best mpg is on nevada gas running over the passes... 6,000 to 9,000 feet... we always expect low mpg there because of thin air and pulling hills, but it's always pretty good..
Over the years, I've seen the higher mpg on those trips in a mazda b2200, an S-10 blazer, a Dodge ram and a Dakota, so it sure isn't just gearing or truck type.. (Sonora pass has a 26% grade.. more fun up than down)
mac
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PLEASE don't remind me of THAT trip over Hwy 108
(Sonora pass has a 26% grade.. more fun up than down)
Driving my old POS 69 Econoline 6 cyl and a 3-speed..the throw-out bearing went south on the wrong side of the Sierra's....and had no choice other than try to make it home to the Bay Area without using the clutch or stopping.....
(It wasn't pretty)
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