1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Gas Mileage

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Old 09-09-02, 09:34 PM
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Gas Mileage

I know my car's exact gas mileage!!
My gas gauge doesn't work so I was thinking about 18-20 mpg. So I fill the tank and think I can get 300 miles, boy was I wrong. I was driving to school and it startes loosing power big time and dies, I pull to the side of the rode and leave it there. I tow it home that night to find it was out of gas.
I put more gas in it and it runs great.

I figure I get 16.666... mpg. Is that good, I don't try and conserve gas at all.
Old 09-09-02, 10:38 PM
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It seems rotaries have a big gulp difference between highway and freeway. On highway, I could get around 30 with my stock 84. I get about 24 with my 85 GSL (power crap). On the highway I was getting about 18.7 with only one ignitor, I replaced it so the car runs like glass. Guess what, down to 15 MPG. I think it's because I am accelerating harder now that she runs smooth and I am using my AC since she idles good now. If I was you, I would assume no more than 15 MPG to be safe. Remember those Nikkis can deliver .34 gallons per minute so go easy.
Old 09-09-02, 10:42 PM
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It depends on what engine and tank you have.

With a 12a I get over 400 miles on a tank while rural driving, dropping to 300-320 in the city.

If you have a 12a then without mods 22-25 mpg would be normal.

At the other end of the spectrum a 13bt ported will get 12-15 mpg.

Thus 16.7 is very poor unless you drive redline most of the time.
Old 09-09-02, 10:52 PM
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I have the 16.8 tank and my 84 could go 365 miles to phoenix AZ and have a quarter tank left. My 85 GSL gets crap for mileage and so does most others who own one that I've talked to. I don't know if it's increased resistance from the hypoid LS diff or the power crap. My timing is perfect, smog is good so I don't know what could be dragging her down. I even ran the carb from my 84 on her and she still drank gas. THere's the possibility of plugged cats, but one cat is new and they passed inspection at the muffler shop.
Old 09-09-02, 11:05 PM
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My 12A streetport would get 25 or so MPG on the highway, 20-22mpg combined city.

Then I moved, and my work was rather close to home. Took all city streets. When the temps dropped, the choke wouldn't release until I was pulling into my parking lot! MPG dropped to a whoppingly poor 9mpg! I took to driving a long, circuitous highway route home just to get the oil warmed up and clear the engine out.

With stock port/stock exhaust/stock everything, MPG tended to be in the 16-17 range mixed driving, 20-22mpg all highway. (I hate city driving and I'd use highways whenever at all possible, so I don't have a city-only figure) That was with the '80. The '85 is stock except for a header, no cats, and an aftermarket muffler, and it also seems to follow this form. I say seems, because all the time i was driving it the T-bar was off and I'd never get more than about 1/3 throttle
Old 09-10-02, 01:20 AM
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the best way to figure out your gas mileage is to fill up the tank then drive 100 miles then fill it back up and divide the miles by the amount of gas used to refill the tank today i drove 95 miles on 4.8 gallons of gas all of it was freeway except for the 50 minute traffic jam
Old 09-10-02, 01:42 AM
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The car has a trip odometer for a REASON

I could get only about 250, maybe 260 miles on the tiny '80 tank before I felt nervous enough to get fuel again. On the 140mi each way trip to my parents', I'd usually fill up before leaving. Then stop 1/2way on the way back home.

With the '85s bigger tank, even though it gets worse mileage I could go the whole weekend with only having to fill up once at home, then once when I got back.
Old 09-10-02, 04:09 AM
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To me a critical point is to never get below 1/3rd of a tank because of potential dirt in the bottom. No fuel filter is ever perfect.
Old 09-10-02, 05:07 AM
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Well, since the fuel pickup is on the bottom of the tank anyway, I doubt it'd much matter Although it would worry me if there was a chance there was water in the tank. Water floats on fuel, so when you get low on fuel you could get a shot of the water floating on top instead of fuel. Engines don't run on water too well...
Old 09-10-02, 01:36 PM
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i have a RB header/pre-silencer, k&n, secondary spring removed, and a 4 spd. and i usually fill up at about 190 or so miles, usually have about 3 or so gallons left in the tank. but i usually get aobut 13 mpg. i drive city allot and highway about 1/3 of the time. hard to get good gas mileage when you are at 4k rpm at 70mph.
Old 09-10-02, 01:59 PM
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In town I get crummy mileage, about 15 mpg or so. On the highway, however, there's a huge difference. I can drive to Calgary, about 6.5 hours from here, on under 2 tanks of gas.
Old 09-10-02, 02:23 PM
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When I first installed my Holley I was running 1.5!! mpg and with help from others (thanks peejay) I am now running 12-14 mpg on hard driving (stop and go).

-Error402
Old 09-10-02, 04:51 PM
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my window sticker on my 82 says 18mpg city, 24mpg hwy. with the dellorto on there, i usually got around 14mpg city, 21mpg hwy until i got the carb fairly tuned. now it's about 16mpg city, 25mpg hwy. on average, lil bit o' city, and a 30 min freeway drive to and from work each day, and a lot of hotfootin' in between, i average 18mpg or so.
Old 09-10-02, 05:47 PM
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i tear *** all over the place and my tank never seems to be empty.

I think i get about 22-25 mpg.

It seemed to get better after all my mods...
Old 09-10-02, 07:38 PM
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What kinda mods do you have4 82streetracer?
Old 09-10-02, 09:16 PM
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I have an 84 se. I think it has a 15 gallon tank and I do have to sit in traffic, that might be why It gets bad gas mileage.
Are there any spots that the fuel sensor wires could corrode and were are they located?
Old 09-10-02, 09:42 PM
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I get about 130 Miles Rural on a Tank on my GSL. Basicaly the carb and intake are so bad it has to be run super rich in order to idle...so untill i can save the $$ for a Holley from racing beat im fillin up every 4 days or so..lol
Old 09-10-02, 10:08 PM
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I get about 250kms to a tank of 50 litres in the city. I haven't done much highway driving in the 7 but I know it's a good deal better than that.

That works out to about 11-12mpg, assuming my maths isn't too bad.

I do tend to drive with the foot to the floor alot though.
Old 09-10-02, 10:27 PM
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Originally posted by peejay
Well, since the fuel pickup is on the bottom of the tank anyway, I doubt it'd much matter Although it would worry me if there was a chance there was water in the tank. Water floats on fuel, so when you get low on fuel you could get a shot of the water floating on top instead of fuel. Engines don't run on water too well...
I think you have that backwards, water is heaver than gas threfore it sits on the bottom of the tank so you'd be screwed if you had a full tank or a 1/3 tank.
Old 09-10-02, 10:45 PM
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Originally posted by S2-13BT

I do tend to drive with the foot to the floor alot though.
Who here doesn't?

I figured I was getting about 12mpg in stop-and-go traffic here... kinda crappy, considering my '86 S10 2.5L gets 25mpg in the same situation.. and produces more torque and HP... just a lot lower geared, so if I were to drag my car, it'd roast me

Jeff
Old 09-11-02, 01:01 AM
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IMHO sports cars, be they FBs or Ferraris, elicit the same fuel economy rated in "who cares/the car drives like hell"
Old 09-11-02, 01:37 AM
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Originally posted by Manntis
IMHO sports cars, be they FBs or Ferraris, elicit the same fuel economy rated in "who cares/the car drives like hell"
Right On! If we where into cars for fuel economy, we would all subscribe to the Hyundai Excell Forum...

Last edited by RACavanaugh; 09-11-02 at 01:40 AM.
Old 09-11-02, 02:05 AM
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Originally posted by Manntis
IMHO sports cars, be they FBs or Ferraris, elicit the same fuel economy rated in "who cares/the car drives like hell"
Drive 3000 miles a month and tell me fuel economy doesn't matter

Poor fuel economy means it costs too much to drive... costs too much to drive means less driving... less driving is a Very Bad Thing.
Old 09-11-02, 03:08 AM
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82-13bt if I remember our brief conversation you have a ported engine which can use up the fuel. Thus only 250km a tank.

Canberra is not really city driving, the old definition of a Canberra traffic jam is a car ahead of you at the traffic lights in the peak hour!

I can easily get to Hay just over 530 km [340 miles]away on a 55 litre tank, but do not risk Balranald the next town at 650km. Its a good run cruising at 110-120 kph.

If you ever do the trip slow down at the Victorian state border, i got booked for 109 in a 100 zone on a Sunday afternoon with no traffic in sight on a straight road- the police are putting speed cameras behind bushes!

Last edited by PaulFitzwarryne; 09-11-02 at 03:17 AM.
Old 09-11-02, 11:37 AM
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Were I driving 3,000 miles per month in a sports car I'd have bigger problems than not enough gas money

But really, one should buy what one can afford, including fuel, upkeep, etc. I briefly flirted with owning a Lotus Esprit (used) but spoke with many owners and those cars manufactured during the Chapman era were like British versions of classic Ferraris - they'd be in the shop more often than on the road.

Given how cheap fuel is in the US I'd think 13 mpg was no big deal to an enthusiast in that country. I can understand groans in Italy, where fuel costs five times as much...


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