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My gas mileage seems unrealistic....


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Stopped at the shell yesterday on the way to KY, put $20 in the tank. Drove the 55 miles to Pineville, then drove 57 miles back to the house, and then another 7 miles to and from the Verizon store. Then today drove the 57 miles to Pineville, and then the 55 miles to the shell because I was empty again. That 6.3 gallons of gas got me 231 miles. That's 460 miles to a tank, and that's 36mpg overall. This is unbelievable to me because it now has a four speed transmission so I'm lacking a good highway gear, it runs pretty high rpms on the highway. I also need to readjust my carb slightly, and I need a smaller idle jet. This is an '84 hardtop with a 1.8 and a rebuilt Weber. Most of the time I average about 30 but that's mixed, this was all highway. What the hell should I expect if I drop another 5 speed and throttle body injection?? I'm guessing freaking 40. Is my gas mileage realistic? Am I doing something wrong? I'm using mapquest to figure the distance. I'm having a hard time believing I'm getting that kind of mileage because it doesn't seem to run that great honestly.

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609 km to run out of fuel in one EA81 Brumby/BRAT running std tyres, look at 55 litres to refill - all highway running at about the 60 mph mark.

Jetting ?? oops, this was standard Hitachi and was on fresh full rebuild minus a crank pin grind - all it needed was a linish, 20/60 cam and 4 speed DR.

 

$3 a US gallon ! Kill for that almost !! A$1.68 per litre here with exchange rate - aussie dollar buys about 88 US cents ...

Edited by jono
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That sounds great! How is your Weber jetted?

I don't remember honestly, I have it written down but it was all pretty much exactly what Redline/Weber calls for except I remember the idle jets were a tad too big.

 

 

probably high because your measure relied on guessing the end point of fuel consumption was the same as starting point.

I put $20 in it at the same gas station paying the same amount per gallon and it put me exactly at a half tank again. This gas gauge has always been really accurate, unlike my EJs.

Edited by Subaru_dude
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I can tell you directly from experience, that's nowhere near true.

 

4th in the 4 spd is nearly the same as 5th in the 5spd.  But the 5spd is a bit taller.  .780:1 5spd  vs. .885:1 for the 4spd.

 

 

But the jump from 3rd to 4th is very large......like going from 3rd to 5th w/ the 5spd.

 

4spd:

3rd = 1.26:1

4th = .885:1

 

5spd

3rd = 1.366:1

4th = .972:1

5th = .780:1

 

I put $20 in it at the same gas station paying the same amount per gallon and it put me exactly at a half tank again. This gas gauge has always been really accurate, unlike my EJs.

 

This is not an accurate way to measure.  You don't know how much gas is in there at "empty" before you put 20 in to get to "half a tank"

 

Even an accurate gas gauge can be off by a few gallons.....espescially near the middle......"halfway" could be 6 gallons, could be 8.

 

I'm sure your getting good mileage, but I'm guessing that these #s are padded a bit by the variations of partial fills, unknown excact mileage, and only based on 1 or 2 half fills.

 

Get the app "mileage keeper"

 

Enter your odometer # and amount of gas every time you put gas in......after a while, espescially if you do complete fillups a few times you will get an average mileage #

 

 

I've been tracking my EJ18 swapped GL for about 4 mounts now.  I'm on;y getting 19.3 MPG.  I drive fast, High RPMs, tow trailers, and I have 215/60/15 tires (my ODO is correct cause I have an outback 4.11 5spd)

 

but still, I've purchased 143.45 gallons and have gone 3159 miles on that. And there is still half a tank in the car.

 

Hmm......now that I do some math that gives~ 22 mpg.....I wonder why the app is telling me 19.3???  Anyhow it's nice to have the app to enter the data every time I buy gas.

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I think you're looking at 4wd transmissions. I NEVER have to gear down for mountains anymore, and I've been passed by Honda Civics I could plainly see were doing 60 and my car is screaming. I drive up a "mountain" everyday and with the 5spd I had to gear down to 4th, now I think if I tried to downshift I'd blow a hose or something. Also, my spedometer/odometer does not work and this is a DL with no tach. That's why I have to use the speed of other vehicles for reference, and those newer model Honda civics are a good reference with those huge digital dashes. You could very well be right about the gauge not being accurate I guess, but back when I had the money to fill it to the brim, $41 and some change consistently topped it off from E with gas right at $3/gallon. But one thing is definitely for sure, ever since the 4 speed swap $20 consistently gets me anywhere from 215 to 230 miles. If the gauge wasn't reading accurately and I was getting less mileage, I would think I would run out of gas despite what the gauge says correct?? There would be quite a deficit building up, and I would have hit the Empty wall by now. I was thinking maybe these engines with the Weber prefer higher rpms on the highway? With the 5 speed I was constantly shifting between 4th and 5th gear because the entire 57 miles to work is hilly and curvy, and by my jerry-rigged calculations I was getting 33. Now that I'm running nice high RPMs and I don't have to worry about shifting, I'm getting further to a tank it seems...

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I average 28mpg city and from 30-35 on hwy in 84 E81 4x4 1.8L engine. the variance is from the gas. non-ethanol 92 octane gets me about 5 more miles to the gallon on hwy, and I get more power too. sure wish there was 95 on the west coast!

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