I dont have much opinion on the gas mileage quoted by this tune, however, the Auto ECO states 38 on the window sticker, if Im not mistaken. The 6MT lists 42. Now owning and tuning over a dozen forced induction cars. I will tell you that there is a lot to be had when you start tuning the ECU. The factory sets the ECU up for extreme longevity. Most tuning can be gained by leaning the fuel mixture out from what the factory sets it at. All cars run on the rich side from the factory, on purpose, so you can drive them at all elevations and the air fuel mixture is still at a safe level. Driving a car at 6,000 feet with thinner air makes a hige difference in the way the engine performs.
In this tune, it seems that most, if not all of the tuning has been done by datalogging the car at various levels while leaning out the fuel mixture. The other is done by simultaneously raising the boost level to 20PSI. Data logging the runs, you can add and remove fuel at certain RPM points to tune for optimum performance. This car has a long way to go with tuning. Turbo charged cars from the factory are very easy to tune and no one has even cracked the surface of this car. It hasnt really caught on yet. I emailed a few turbo builders that I know, and they have nothing on the drawing board for this car. I dont know how easy its going to be to get turbo builders to do something with this turbo. They are used to messing with Garrett and Mitsubishi turbos. Honeywell is one of the biggest manufacturers of turbos, so I have no doubt that there will be options eventually. I just dont see this car going dead in the water anytime soon.
Now, depending on just how lean this car really runs from the factory may mean a few things. Chevy has purposely detuned the vehicle to allow the vehicle to grow in its class. If they come out with the 2013 Cruze and it gets 46MPG, they dont have to do anything except tune the ecu a little. A manual getting 42 MPG and a Trifecta tuned Eco getting 48, isnt that much of a change. With the boost turned up, the car is going to be making much more power, which is also easier for the engine to get up to speed. So with that, I think its possible with the right tuning. Not all cars are the same from the factory. This is why the EPA gives you an average. The factory would be getting hammered advertising a car getting 50MPG when thats the theoretical max. Cars simply will not get the same gas mileage as they did in the mid 1990s and 2000s. Cars today are so much safer than cars from 10 years ago. Cars back then had no airbags, today this one has 10. 5 Star crash safety rating across the board with the exception of roll over. most didnt have ABS, traction control, or anything like that. So things have changed. With the safety standards of the mid 90s, this car would get 60MPG all the time.