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What's sad about it is you could have put an original GM LT1 or LS1 type engine back in the car, and got nearly the same mileage with about 300+ HP.
(Note these two engines weren't available for that year)
 

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I'd have expected more mpg from a car that slippery.
Maybe it's gearing holding it back.
 

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1850 RPM's at 65MPH in OD. Seems to be almost ideal. I'm surprised too as to why MPG is so mediocre. A light pick-up truck should get that - I was expecting a car to do better.
 

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What's sad about it is you could have put an original GM LT1 or LS1 type engine back in the car, and got nearly the same mileage with about 300+ HP.
(Note these two engines weren't available for that year)
\\

30 mpg with an LT1---no way! I put one in a Vega, much lighter than a Firebird, and only got 17 mpg avg.. 3.08 gears 26" tire dia. no overdrive. High 11's, and low 12's in the quarter though. I did have my foot in it most of the time though. But even with a light foot, it wouldn't get better than 20mpg--ever.
Bob B.
 

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I bet it gets better mileage, he probably just can't resist doing burnouts around every corner :)
 

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I had a 94 LT1 Trans Am that got 27 on the highway during the day (it lost 3 mpg at night when the lights were up). With some custom tuning and lower gears, it would have seen 30 mpg with the LT1. Where the mileage will show up with that 4bt Firebird will be around town. People in my family have owned 3 Firebirds and none got better than 14 in town driving.

As far as fit, isn't the 4bt a bit narrower than a V8? You've got to have some tiny, flexible hands to change all those spark plugs. Another thing you wouldn't have to worry about with a 4bt :)
 

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my 95 Impala SS got 30mpg on the highway... not so much in town tho...
 
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