Hey guys newbie here just got an 84 Z28 305 HO a couple weeks ago and the gas mileage sucks bad. I changed the air filter and seafoamed the carbeurator and im driving like a grandma and still only get about 15mpg. what else can I do to increase gas mileage? My tires are inflated properly and just did an oil change.

 

Are you getting 15 on street I think that's good

 

im not to sure there is much you can do, that is pretty good for a carb. what kind of gears do you have in the rear end?

 

If you're only driving in town, 15 is reasonable. But out on the open highway, you should be able to get 25 mpg. You didn't mention a tune-up, and you should also do a new Exhaust Gas Oxygen sensor. It's in the driver's-side exhaust manifold.

 

a exhaust gas sensor..? hm ive seafoamed the carbeurator and put in a new air filter and changed the oil.. gonna get a new cap and rotor then later plugs and wires but how bout a mass air flow sensor? do i even have one if so where is it located? in case anyone forgot i have an 84 Z28 high output. oh another question i have 215s in the front and 235s in the back 215s call for 44psi and 235s call for 35psi i have 40 psi all way round should i do 44 in front and 35 in back or leave it like it is? im getn 13 mpg and i think it has 3:73 gears

 

MAF is on a TPI car - you are carbed so no MAF. Plugs, wires, dist cap, rotor - basic tune up is about it. Change fuel filter. Check/set timing. Atilla means O2 sensor.

 

I speak for myself only here, but I personally would follow the recommended tire pressures (44 up front and 35 in the rear). Your tires are rated to operate at their best at those pressures. There is no need to fool with tire pressure on a daily driver, that's more of a track/racing thing. JMO

 

The front tires are smaller, and are carrying more weight, so 44 up front, and 35 in back, seems best to me. If you run the rear tires overinflated, the center of the tread will wear fast even if you don't spin the tires.

 

sorry there isn't much... you can spend alot of money on a few miles per gallon upgrade or get a prius.. i've always thought if you can't afford the gas you need a better job...lol enjoy the car thats what its about

 

you could spend some money and put fuel injection on it, you might touch 25 if you drive it conservatively with that upgrade. But i wouldnt think itd be worth the money or hassle, just a thought.

 

Not sure where you're coming up iwth those numbers, should be 35/35 for the 84's. At least that's what my 84 T/A says on the door for any size tire. Of course it is pretty faded and I can only read the numbers for the PSI just barely. I'm running 235/60/15's and was running the 215/65/15's before and ran 35 all around.

Other than that, I completely agree with the tune up. Plugs, wires, cap, and rotor. Also an O2 sensor (LOL Atilla using big words in his first post!) Before I swapped in my 350, I would get 15-17 in town and 22-25 on the highway with the cruise set at 65 with my L69 305 and 3.73's.

 

if your talking about the pressure written on the tire that's max pressure 44 psi is high I run 35 psi all around with stock size 15's.

 

Yes, don't go by the pressure on the tire...that's MAX...never inflate over that, could cause an explosive unseating of the bead. People lose fingers and hands when that happens. The numbers to go by are on the door near the latch (on the end of the door where the striker actually latches the door closed). There should be a sticker that has stuff like vehicle weight, weight distribution, and tire pressure. Should say 35psi.

 

yes, big no-no running max tire pressures. I usually fill to 75% psi on a cold tire.

Like above, 15 mpg in the city isn't horrible. I think a better indication would be a highway trip.

Definately finish the tune-up and post back.

 

It's always best to use the vehicles recommended air pressure. Too much or too little and you'll wear your tires out faster. Also, keep them rotated every oil change or 3000 miles. This will ensure max life from the tires.

 

My brother had an 85 Camaro and he would get around 18 mpg. He did a lot of city as well as highway driving. I would think that 15 mpg is a bit on the low side of gas mileage. I know that in my 91 Firebird with a 305 I would average about 21 mpg with a combo of city and highway. My only good suggestion besides those that have already been given is to keep your foot out of it at all costs and continue to drive like a grandma.

 

I don't drive conservative by any means and I get 17. I do have TPI though.

 

I have an 86 with a tweaked LG4, and I probably get about the same mpg. Carbed 305's just arn't as efficient as fuelies. I have tuned it, but i haven't changed the o2 sensor. I thought a bad 02 sensor would cause the engine to run rough, not just get bad mileage. Correct me if I'm wrong.