Batass

I've been out of the loop for a while. I remember gen III cars getting close to 30mpg with the T56.

What are they getting now? I see they are rated 27 highway. That number was less for the gen III cars but I know they changed their calculation formula.

So far it seems that a well tuned gen III engine is very close in mpg to a newer vehicle. Power however is much improved.

RPM WS6

iTrader: (3)

MPG is about more than just the engine; many other vehicle factors will have an impact. You can't directly compare fuel efficiency of two engines unless they have been installed in an otherwise same vehicle.

Batass

Yea....not much difference from car to car. Aerodynamics are very similar.
Rear axle efficiency plays a small role, but what factory GM car runs the high drag 9" ford??

Transmission, big part sure.

Wild guess, but I would say a Corvette, a camaro, an SS, a G8 GT, and a CTS-V would all get very similar mpg given the same engine and transmission. Neat.

RPM WS6

iTrader: (3)

So what are you comparing then? Moderns cars to each other, or those modern platforms (with different weight, different transmissions, and a different engine) to the older 4th gen F-bodies/C5s?

I guess I don't understand what you're asking or trying to compare here?

Batass

Say the camaro gen v to gen iv. I hear the autos now do just as well or better than a manual....

Or, how much of a mileage gain would a guy get if he swapped out his ls2 manual in a cts-v to an LT-1 with a manual?

Im just curious. If I swapped out to a modern engine, it would be the 6.6, if anything.

67_ls1

I went with an LFX V6 and a 6 speed auto in an attempt to get max mpg out of my 66 Chevelle daily driver. It’s about 750 lbs lighter than the 2013 Camaro donor but not near as aerodynamic.
I tried to stay as close as possible to the Camaro's rear end ratio but couldn’t fit the same diameter tires so there is a difference there.
The Camaro was rated 30 mpg highway so I thought I would shoot for 35 mpg in the Chevelle by being super light. That didn’t work.
If I drive for mpg I get right at 32 which isn’t bad. I’m trying to figure out a front air dam to try and keep more air out from under the car and hope that will help.

Batass

I think aerodynamics have much more effect than weight. Once you're already moving, weight doesnt matter much. I found at cruising speed, with 3000 lbs in the bed of my truck, my mileage almost stayed the same.

It used to be that you could get better mpg than what the sticker said. It seems now that it is much closer to actual.

I'm guessing a v8 would be very similar mpg under cruising conditions and much worse in heavy stop and go.

99 Black Bird T/A

iTrader: (4)

Had a rental 2019 SS Camaro convertible, A10 for a few days and it seemed to get ~27-28 mpg highway.

My 02 Z28 A4 gets 27.5 mpg highway but has 2.73 gears and is several hundred pounds lighter.

Stock my 99 TA M6 hit 31-32 mpg highway many times.

Stock my 91 RS with a 305 TBI, 700R4. A4 & 2.73 rear gear got 32+ mpg highway many times.

Doesn't seem to me mpg has changed much over the last 30 years but power has greatly increased.

Batass

That does seem to be the case. After a tune I get 17mpg with my lq4 and 3.73 gears in my truck. Up from 13.
I bet if it had a 6l80 or a better OD, I would be very close to what the newer trucks are getting.

I see the little cars are getting around 40, but my last few econoboxes from late 90s/early 2k were getting 35ish with some simple mods and snow tires.