OK, 89 GTA/auto with the stock TPI-350, and 3.27 gears, what kind of mileage should i be getting with this car? Of course that would be driving like a normal, sane human being . It just seems like it is sucking a lot of gas. New injectors, and tune up. Also 106,000 miles if that helps.

 

My car gets about 21 MPG highway and around 14 city. I have 3.27 gears, and the mileage was the same with the stock engine too.

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Black 88 GTA L98
New engine is in!
ZZ4 bottom end, Edelbrock 6085 heads, LT4 HOT cam, GMPP 1.6 RR's, ported stock TPI, SLP 1 3/4" headers, no cat, Dynomax cat-back
E.T.F.A Member #11

 

I get just a hair over 20 with my formula. 305 5spd and 3.45 gears

 

Well, I used to go from Miami, Fl to Moroso Motorsports Park in Palm Beach, FL to have fun at the track and the drive was 110 miles each way. I would put 5 gallons on the way back and drive at 75 MPH with the occasional high speed burst and would make it all the way home. If you divide 110 miles by 5 gallons that's 22 MPG.
On the city, the beast sucks gas like crazy. I think I get about 10 MPG, but you have to consider that I do have a very heavy foot

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'88 GTA 350
Headers, catback, free mods, Xtreme energy cam, and intake pieces
13.51@104.27, but can run better as it is.

New 2100-2300 RPM converter is in. Hoping for 13.30 or better.

 

Sometimes I even race my shadow!

hehehe

 

With my 89 IROC withe L98 and 2.77's I get 16-18 city and 26-28 freeway...depending how i treat her.

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1989 IROCZ28, 5.7 liter TPI, 700R-4, 2.77 Rear, Gutted Air Boxes, Flowmaster 80 series muffler with dual 3 1/2" tips, Clarion 8575 Head, Infintiy Kappa 4x6 plates, Stock 6x9's, Alumapro 10" Aluminum Sub in sealed box, Orion 400 watt amp

 

I generally get 23-25 (highway) and 15-18 (city). The best highway I ever got was 26.5 and the worst city 13.

Mine is a basically stock 350 with over 160,000 miles (262,000 Kms), minor bolt-ons, auto, and 3.23s (at the moment).


[This message has been edited by Glenn91L98GTA (edited November 30, 2000).]

 

Believe it or not, with all my mods I get 27 Hwy and usually 20-23 around town. Thats with an auto and 3.27's. Don't ask how, I must have just the right combination of parts and perfect tuning.

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88'TA 305TPI 330HP, NATURALLY ASPIRATED, PASSES N.J. EMMISIONS. "I AM JUST THAT GOOD"

 

...

[This message has been edited by irocbsa (edited December 01, 2000).]

 

With my mods and 2.73s I have gotten a best of 27 on the highway. I usually only see about 12 around town though witha best of 15....
bsa

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"If they do not run, Then they will die." - Stonewall Jackson

'87 IROC, 355 TPI,700R4, Trick Flow Heads, Comp Cam, Comp 1.6 Rockers, Lucas 23# injectors, Edelbrock headers, Flowmaster 3'' exhaust, gutted cat,
Mallory coil, Mallory HyFire IV ignition box, Mallory Sidewinder 8mm wires, Autolite platinum plugs, K&N filters, Transgo Performance Shift Kit, Corvette Servo, 2,000 Torque Converter

 

Well I'm usually standing on the throttle being that it's mostly my "weekend cruiser" but I'm only around 9-12 in the city and I have no clue on the highway.

 

On the highway with cruise control, I've gotten as high as 25 mpg. 22-23 mpg is pretty typical for me for mostly highway driving.

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1989 Formula WS6 M5
SLP cold air induction, K&N filter, TPIS modified MAF, TPIS 52mm TB w/ airfoil, Random Tech cats, SLP cat-back, TPIS AFPR, March underdrive pulley, Accel 300+ coil & 8.8mm wires, Bosch Platinum+4 plugs, Hypertech 160°F t-stat & fan switch, Hypertech Streetrunner chip, Centerforce dual-friction clutch, PST front suspension kit, PowerStop cross-drilled rotors, Porterfield Carbon Kevlar pads, Russell SS brake lines, Firehawk SZ50 EP P255/50ZR16.

G-Tech Pro measurements:
0-60 mph: 6.0 sec
212 RWHP

1/8 mile results: 9.74 sec @ 74.5 mph; 0-60 ft @ 2.35 sec; +0.46 reaction

2001 Trans Am WS6 A4
Stock

More info at website:
www.fbody.com/members/stevenmh

 

Basically stock, 89 GTA, 350TPI, auto, 3.27 rear, 15 city, 21 highway. It boggles my mind how my brother's 305 TBI can get 27mpg on the highway with 3.73's, and I can only manage 21mpg with 3.27's. I think the 350's are just really bad on gas, but it's worth it.

89 Transam GTA, a few bolt ons

 

I get 26-27 on the highway and 18-19 in the city...and thats with my umm...semi-lead foot...hehe

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89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-700R4 (Rebuilt) Too much done to actually list
-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)
-MSD 8.5 mm plug wires
-Problems every other day with the car (probably not a mod, but to me it sure makes a difference)

 

I get 17-19 hwy/city sorry I do not have split figures, I have not taken it on any road trips since all the mods/installations.

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'84Z28/'92 305TPI
'92 complete rear suspension/PBR disc/Posi/3:42
Light weight 34.5mm stabilizer bar in front
23mm sta. bar in rear
rear lowered 1" by cutting 1 1/4 coils of '84Z28 springs
comp cam, flowmaster
TB coolantbypass/shutoff valve to heater core
MAT relocated
Ram-Air(home-made) gutted air-box
IROC ground effects/wheels GY245/50's
700R4 superior shift kit/ corvette servo(excellent shift kit
Rebuilt engine and transplanted it myself. Love this engine!
freshly painted OCT. 2000 bluegreen with two white stripes on the hood and deck lid
LOW performance people should drive low performance vehicles!

 

When I was in Oregon traveling from Eugene to Portland I would get 27 on the highway but only 15-18 in city. I seen the bigest increase in mileage when I changed the air filter to a K&N one. Now that I am in Texas and have a company car I have not driven it that much to check it.

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89 GTA
350
K&N air filter
Flowmaster muffler

 

I get 20 mpg average (hwy in rush hour).

* 87 Formula 350 (auto)
* synthetic oil for last 150K mi/9 yrs
* 3.27 gears

 

well, thanks for all your replies. They tell me something is very wrong with my car. Im getting around 10 mpg no matter how easy i drive it. Could a bad O2 sensor cause this? Also could it cause a rough idle? How about IAC? Is there any way to test either or do i have to go and buy new ones? What does an O2 cost anyway?

 

My numbers are in line with the others. Mine is a base 305 w/carb, 5 speed '85 T/A. Around 19 or so city, a high of almost 26 on highway. O2 sensor not expensive, easy to replace. Looks like a fancy spark plug, in your exhaust piping somewhere, with a wire coming out of it. I would think you might have a code show thru your ecm & "check engine" light if it was bad. A cheap fix, anyway, worth trying.

 

I'm looking at 8mpg town 13 highway


I do have a heavy foot but it still shouldnt be that bad. Maybe I'm doing it wrong. I usually get 50 miles for every $10 of gas at about $1.67/gallon

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1987 Firebird Formula 350[*]Stock except...[*]Cragar Street Stars
My Car Website w/ Pics
fyrebird350@hotmail.com
AIM/AOL: FIREBERD350
<<<<---THIS CAR IS FOR SALE(only 49k)--->>>>

 

I just checked mine, I get like 17 average with a ton of city/traffic driving. Gotta love New York. That's with 100k miles on the thing and leaky valves, and my semi heavy foot.

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-80 Camaro 350, Carter AFB, headers, dual exh, ram air, all sorts of crap
-88 Iroc-Z 350tpi, 3.27 gears, 4 wheel disc, MSD 6a, tpi airfoil, k+n's, white gauges, accel coil, flowmaster, pretty quick