Okay when I first got the car I would max out at 240. Then I put in 87 octane, unbolted the catback, added a cold air intake, and use Mobil 1 synthetic <-------if that does anything. And I set cruise at 70-75mph for 95% highway driving and I finally break 300 miles and finish with 311.7. My car has an auto tranny with 2.73's.

With that said, shouldn't I get better mpg? I mean that's really not even 20mpg on the highway. Didn't these cars get 25 or so on the highway? The car runs fine but pops when I let off the gas, doesn't that mean a "rich" condition? I read that on here somewhere, that the popping when letting off the gas means a rich condition? Anyway, I shall get a gallon of acetone tomorrow and add 1.5oz to my tank before I fill up.

How can I tune my car to run more fuel efficient? Will proper spark gap help? I believe mine are set at 40>.

Thanks!

 

try slowing down to 60 and see what happens, I would also lean the carb out some, check the timming and the gaps of the plug.

make sur the engine stays cool--loose some weight(the car) fiber glass pices ect. allum drive shaft and drums--1 pound of rolling weight is = to 10 lbs of dead weight

later and


GB

rlk

 

Car is TPI. It has the stock alum DS and alum drums. I'm not desperate for crazy MPG and driving 60mph is pretty UNSAFE here in Phoenix, considering the slow lane is 70mph, where I keep it.

Is that good for the age of these cars now? I hope not, 20mpg highway is 20% lower than stock.

 

Well I know that 60 deal is also unsafe in the cities in MN I would maybe put in a six speed and ifg you could lower the car that will help the aero of it . the octane will effect the millage if the car needs a higher octane. Keep in mind that our cars are not new anymore where and tear has its effects. have you done anything to the motor to make it more efficent-- If it has many miles on it a valve job will help. A gear vender over under drive will double your gears. a turbo will give better milage.

what do you want to achive

later and

GB

rick

 

Not too bad. I was able to go past 400 though on a car I used to have.

How is it you figure 20mpg? Are you completely emptying the tank?

 

well I just got 13.8mpg in my tpi pickup. It has 3.08 gears, but that was mixed driving. I'm trying to up the mileage. (heck I was getting 11mpg with a carbed 327 with a cam and TH350).

Anyways, I'm going to get some GM Top End cleaner, I put in some fuel injector cleaner, and next tank I'll switch to Premium....see if any of that helps.

 

dont wanna sound rude but the if you wanted fuel economy you got the wrong car. although i see where your coming from with gas priced as high as it is. i say screw gas prices just enjoy the car.

 

Rick, besides the CAI and unbolting the exhaust, the car is stock. I understand wear and tear. Now I have a question. I work roughly 25 miles away. 20 of those miles is highway and 5 are street to the freeway. Now would that mean that I only drive 80% highway, right? So If I were to drive to San Diego and stay on the highway the whole time, I would get roughly 20% better correct?

Madmax, I fill up at the same point, 2 ticks below empty. I can go further but I don't want to risk running out of gas and not having the car start.

Ackattack, I was thinking of getting some GM top engine cleaner, but I heard they no longer sell it for 1 reason or another.

A88GTA, I didn't buy the car for fuel economy, I need to get a 2nd car -OR- get a job closer to home. Buuuuuuuut, until that happens......when in Rome.

 

It really doesn't tell you much that you filled up at such and such point on the fuel guage, those things are very inacurate. The proper way to figure your gas milage is to start with a topped off tank and drive however long you want, then top it off again and divide the miles driven by the gallons you put in the tank. So your 300 miles could be 20mpg if you put in 15 gallons or it could be 25mpg if you put in 12 gallons.

 

Well those 25 mpg ratings from the factory are rated at 55 mph, where you turn very little rpm vs speed. Once you get past 60, the rpm's start to climb. 20 mpg isn't too bad, just make sure you have the normal tuning req. done already. G'luck!

 

BmonteSS, I always fill the tank and it's always within 1/2 gallon with the last tank when I filler' up.

87TPI350kid, that was gonna be my next question. 'What is the speed the factory gets their numbers from?' and that makes sense. I mean back in 1991 the Speed Limit on the highway was 55mph. Now it's 65-75mph. That also makes me feel better. Because I don't abuse the car. And it runs awesome.

And I actually got to 313.8. I stopped off at Home Depot to get some acetone before I stopped off at the Gas Station. Unfortunately I was only able to put in $6 so I couldn't use the acetone. I even had my little 1.5oz marked bottle with me.

I will get some numbers for you guys next week sometime.

 

maybe, maybe not all of this depends on the gearing and the rpms required by the motor to go those speeds. (i am sure you already knew that) however we did put in a tornado in the 94 taurus and on long trips at 75 mph we gained 3 miles to the gallon from 24 to 27. we only get about 12 in town with the car driving it nicly with the stop and go

then why are we doing this?
later and
GB

rick

 

yeah my tank guage is all over the place.. i start the car up sometimes and its 1/2 tank for 5 minutes adn then drops to 1/4 or less. LOL

i used to get around 18mpg a gallon with the catback and 2.77 gears... no converter.

i dropped to about 16 i think with some spirited driving. i havent really checked

 

Wow I didnt know that a restriction in the air intake got better gas milage.

 

I would think you'd be able to do a little better than 20 on the highway. Good tuneup is important- including things like cleaning out the TB, getting the injectors cleaned, setting the TPS properly, putting in a new O2 sensor, doing a diagnostic scan to make sure everything is reading "sane" while driving around, etc. More than just plugs, wires, cap & rotor. I haven't found a TPI car in the last 5-6 years (stock or not) that didn't have at least ONE thing out of whack on it, usually multiple things- almost none of which set a code or caused any serious drivability problems.

Here's an example of fuel economy I've been through recently, although not a TPI engine: 1985 Camaro with an original LG-4 305 computer controlled carburetor engine. Ran bad, leaked oil, got bad mileage. Fixed the oil leak (fuel pump bad internally) and suddenly the engine ran a little better (old pump was not providing adequate fuel pressure). Did plugs & wires- little better still. Did new coil, cap & rotor and got a noticable improvement. Checked the timing and found it to be retarded- reset back to factory spec of 0* and suddenly the engine grew some *****. Bumped it up to 4* BTDC and it got even stronger so I left it. Mileage improving the whole way. Rebuilt the carb but it didn't help- there was nothign wrong with it in the first place. Found a MASSIVE vacuum leak to the HVAC vacuum reservoir and fixed it- suddenly that sucker idled dead smooth and had much better off-idle throttle response. Replaced all the (miles of) vacuum lines and it stopped throwing intermittent EGR codes. Put in a new O2 sensor with no obvious change but the scan tool said the ECM was leaning out the mixture a little more than before. I'm sure I did some more stuff but I can't remember it all.

End result..... went from getting about 15 MPGs to 25 on the highway (yes- with a CARBURETOR). Imagine that..... put it back the way the factory intended it to be and it gets great mileage. Moral of the story.... poor mileage is often the result of a lot of little things being wrong, rather than one big thing.

 

I'll second that about lowering your car and getting better mileage. Once a month we do an 8 hour Banzai trip, all freeway there and back in one day. After lowering, headers and an airfoil plus pumping up the tires to max air. pressure and setting the cruise control, we averaged 25-27 mpg up from 20-24 previously. That is with two adults and my son in the IROC, running 91 octane. That's still with the occasional race up to the top of the two grades on the way down. We were happy with the 25-27. What is the best mileage you guys get?

 

Well, I'm not real sure what '2 ticks above E' translates to in gallons. You should be using what you put in the tank, gallons wise. You might only be using 10 gallons, I dont know.. but you do. I really doubt though that 2 ticks above E is 15 gallons of gas.

 

i get 10-12 mpg.. lucky 2 break 180 miles on a tank.. quit b*tch'n

 

2 ticks BELOW E. There isn't actual ticks but where 2 ticks would be, do ya follow?

Anyway, acetone is in, car is full 15.5 gallons full. That's what it said at the pump. And I was again, at 2 ticks below E. I hope to see at least 350 this time.

 

Ahhh that makes more sense. Please fire my reader!

 

This is the best way I know to find out what kind of mpg a car is getting:

Fill up car until the pump clicks off. Write down mileage on odometer. Run half of a tank or more out of it. Go back to the SAME pump and fill it up until it clicks off. Write down the number of gallons it took to fill it up and subtract the first odometer reading from the new odometer reading. Now divide that answer by the number of gallons used to find out your avg. miles per gallon.

I used to have a car with a broken fuel gauge, so I had to use the odometer as a fuel guage.

 

Although it warns me that its getting low by bouncing around a little bit. It gets about 200 before I worry about checking on the tank. Wish it went as fast as the gas does!!!

 

sorry about the crappy milage. i hate to say this but my camaro gets close to 32 mpg on the highway. i have a 89 rs with a 2.8 mpi V6. i still need to do stuff to it to get even better gas milage.
but if u guys want any info what i did to get that out of my engine let me know . my aim is gbm665 leave me a message. well ttyl
joe

 

Honestly the only thing I can think of was forgetting 2 cylinders on the factory floor.... But in all seriousness, the last v6 gm i had had a 3.1 in it and it got as good gas mileage as my 4 cylinder z24.
I wouldnt be suprised tune up and checking vacuum hoses helps. I know I am no expert, but my formy ran like crap till I replaced all the vacuum lines. Still does, but not as bad
Mike

 

Sounds like my old car - but I didn't have a 402. Stupid lil 2.8 Auto running like crap I didn't keep the car long enough to fix it - after all, it was a FI V6 (tho it only had 67K when I bought it three years ago...) avg'd 11.5, best was 13.5 - and no heavy foot.

Do like these guys are saying, use the actual amount of gas put into the tank, and the number of miles that you've driven since last fill-up. It's the only way to know your true MPG's.

 

why would you want the engine to stay cool if your trying to get better gas mileage?

 

a few things I have done to help out with gas mileage on my car

car required regular instead I put premium in there after I did that I upped the timing to compensate for increased octane.
tire pressure was upped a little also to make for less rolling resistance.
leaned out the fuel mixture a tad bit.
running full synthetic 5w-30 in the transmission.

just the timing, synthetic in the tranny, and slightly more air in the tires made me go from 33mpg on avg up to 38mpg avg

still waiting for the acetone to see what the gas mileage difference would be but wonder how much of a difference it is going to make being the car has 2 month old gas in it and I'm not sure how that is going to affect anything.

 

I've gotten 380 miles out of a tank, with still around 2 gallons left. That was all highway, cruising at 80 mph.

Car gets it's best mileage at about 80 - T56 in 6th gear with 3.27 gears.

Thing is I have a weird 18.5 or so gas tank.