All things being equal (car, trans., rear gears and driving style) does 4-5 mpg sound right between a 305 and 350? Also, all things being equal, does 2 mpg sound right between 3.42s and 3.73s?

 

All things being equal a 305 and 350 can get the same, and same with the gears. I went from 2:73s to 3:73s and didn't drop any.

 

Never heard that before. If that is the case, why did they even sell cars with 305s and 2.73s?

 

My guess would be emission purposes and the price of the car for the public. Offering 2:73s I'm guessing because it matched the powerband of the motor better.

 

If a 305 gives off less emissions does that not mean it uses less fuel per unit of time? It does not cost more to make 350s than 305s. They charge more because they can get away with it. Anyone else can chime in here.

 

Maybe not, but offering a 350 included a premium that they could charge for performance. There's no reason a 350 and 305 can't get the same mpg, with all being equal.

 

I disagree with that. I lost 2mpg going from 2.73's to 3.23's (highway mileage). My city mileage, however, stayed the same

as for the 305/350 question, I don't have any hard data, but I would be inclined to agree with that, except I would say a 350 can get NEARLY the same as a 305

 

I actually got better mileage going from 3.23 to 3.73 with my wee-05. That is city though, I dont do too much expressway driving...so I couldnt tell ya.

 

I guess that could make sense. The lower gears makes stop and go travel easier on the engine and it uses less fuel. And if you ran a tank with each just riding the freeway only the opposite would occur. The higher gears take advantage of the engine not being asked for much power and allow the engine to turn less rpms per mile thereby using less fuel. It seems that fuel economy as it relates to gears depends on who you are.

 

when i switched from 2.73's tro 3.54s my mileage stayed the same for highway, around town it suffered for a while cause i played with my new launch too much.
a 305 and a 350 woudl get the same mileage, mayeb a tiny difference, but nothing that woudl be noticable.
i seem to remeber the EPA ratings of LB9's and L98's being teh same or similar, not 100% on that though. anyoen know?

later
tim

 

EPA numbers don't really work for this scenario (all things being equal) as the EPA will explain themselves. They are rough numbers based on average vehicles and only deal with engine and transmission combos. The don't deal with gear ratios, weight, wind resistance and other factors. Cars with the same combos were stickered with the same numbers even though one may have been a trim Formula for example and the other a heavy GTA. You can't compare the 305 and 350 with the EPA numbers even if you ignore factors such as weight because they did not come with the same gear ratios.