Since everyone is talking about gas mileage, I’m just wondering what a stock 305 and stock 350 v8 should be getting in average mileage.

Second, what have most people done to improve their vehicles mileage, and does adding performance parts decrease or increase it? For example, the usual Open Element, Headers, Cat back and 3inch to dual exhaust.


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un4givin89



1989 Camaro Ralley Sport
305 TBI
Edelbrock Open Element Elite Series
1 1/2 lowering springs
Hooker Shorty Headers
Str8 3inch Pipes No Cat
Flowmaster series 40 muffler with dual outlet.
www.mikekey.net

[This message has been edited by un4givin89 (edited September 25, 2001).]

 

On a trip from Jacksonville FL to Oceanside CA my 89 5.0 TBI got between 25 and 27. That was with the cruise set at 75.

Phil



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89 IROC 5.0 TBI
89 RS 5.0 TBI, T-Tops, Soon to be a IROC clone.

 

The camaro with a 305 and a few mods gets about the same as the bone-stock formula with a 350: 16 in the city, and 22 on the highway (at about 75 mph). As for mods that improve gas mileage, headers and other free-flowing exhaust components help a lot. I gained almost 2mpg on the highway when I put headers on my camaro. Hehe, then I lost about 3 mpg after putting in a cam, stall, and 3.73s. Upgrading the ignition will help as well. And although I've never heard or read this anywhere, cleaning and flowmatching the injectors ought to help also.

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Michelle
92 Formula 350
91 Z28

 

The single modification that gave me the greatest increase in gas mileage was "optimizing" my eprom, and then invoking "Highway Mode". I run around 17.2:1 with 47* spark advance in part throttle cruise.

 

I have a 84 with the LG4 305 and I get 17 - 18 MPG around town and 25 MPG on the highway. My main mods include Dynomax headers and catback, comp cams XE250, and home ported heads (416s). That goes through my T5 and 3.23 rear.

 

Get between 27-29mpg on the freewat @ 75. About 20-22 in town. Car has 102K on it now. Also 2.73 rear gears. The rest in noted in the sig. at the bottom.

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'92 firebird t-tops
305tbi,670cfm tbi, 2 1/2" Dynomax catback, 9x3 K&N open element

 

obviously I meant freeway. not freewat. computer just won't spell well.

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'92 firebird t-tops
305tbi,670cfm tbi, 2 1/2" Dynomax catback, 9x3 K&N open element

 

CLearly a better breathing car does seriously improve Gas mileage.