Hi everyone,

Pontiac trans am GTA 1988 350 5,7 tpi

I was searching for information on how much fuel these engines consume, but I don't trust my terrible math skills when it comes to converting MPG. Here's the actual fuel consumption of my engine: 2.32 liters per 100 kilometers (Converted: 117.61 MPG, although I'm not sure if this conversion is accurate. I apologize).

Is this really how much it should be comsuming? or is my car running to rich?

 

Those ordinarily get about 16 miles per gallon or thereabouts in typical city driving, in like-new condition. That would be in the neighborhood of 7 km per liter. Might be 20 - 25% better than that on the highway, so, perhaps as much as 8 - 9 km per liter.

A Toyota Prius gets around 50 miles per gallon on the highway. So, yeah... Seems like there's more than just arithmetic at question here.

 

I would agree with about 16mpg doing average mostly city driving, I have gotten upwards of 26mpg on the highway (empty car, windows closed t-tops on) although 23mpg with a passenger and cargo, t-tops off is more typical.

I was getting 11-13mpg for the first couple hundred miles after dragging the car out of hibernation.

 

1989 GTA 350/Auto 3.27 rear. When I daily drove it, about 16MPG around town and 20MPG highway. When it became a nice weather car, about 13MPG since when it came it, my driving was more "spirited".

 

There's something off with your initial measurement, for sure. A 2021 Toyota Corolla gets 7.1L/100km. Your initial measurement suggests you're somehow getting around three times better fuel economy than a modern 4 cylinder efficiency vehicle.

How are you getting that initial measurement? I wouldn't trust the fuel gauge on one of these cars for any sort of accurate measurement (for example, a quarter of a tank on the gauge doesn't translate into precisely one quarter of the fuel tank's capacity). If you're starting with a full tank, driving for a bit, then topping it off to see how much you used over X distance, that should give you a better number. The further you drive the more realistic the calculated value will be.

 

A moped might get 2.32L/100KM but not a 1988 V8 in a 3600 pound car

Fuel mileage from that era of cars is usually in the 16-20 MPG(US). It depends on a lot of options such as transmission, gear ratio and driving style. Not doing the math but that would work out to be somewhere in the 12-15L/100KM

My 91 454SS got around 28L/100KM on a good day
My 04 F350 superduty diesel got around 16L/100KM
My 14 F150 with a 6.0L gas engine got around 14L/100KM
My 19 F150 with a 2.7L TT gets around 9L/100KM and has more torque and HP that the 454SS ever had.

Fuel management systems have greatly improved over the years. Yes there were carburated 350's that got 25 MPG back in the days but also belted out a lot of pollution. As engine designs and fuel management changed, power levels went up and fuel mileage got better. I've been watching a few of the Drag N Drive races this year. There are 3000+ HP cars (running on alcohol), that can cruise down the highway getting 20 MPG on gasoline.

As mentioned above, fill the tank and go for a long drive. Refill the tank and record the distance you drove. That's going to give you mileage. The longer distance you drive, the more accurate the result will be.

Third gen fuel tanks are around 60L. If you are getting a good 15L/100KM, a full tank should give you a maximum range of 900KM before it's empty. If you're only getting 12L/100KM then you only have a range of 720KM

 

Im sorry everyone! i typed wrong,

The consumption is 20l/100km

i forgot the extra zero .....

 

That makes better sense. It works out to about 12 miles per gallon, which is lower than the car is capable of, though probably not lower than many of them get nowadays.

As far as "running rich", it's hard to say. An engine can use too much fuel due to running lean, as well. Anything that reduces its efficiency can increase fuel use.

What maintenance has been done to the car? Have the spark plugs, distributor cap, & rotor been replaced? are there any "codes"? how long have you had it? has it always used this much gas? any odors like escaping fuel around it? etc. Details might help you find out whatever it is you want to know.