Originally Posted by G.Subramaniam
Does the WRX / GT give less mileage than the RS, and by how much
Does increasing compression increase mileage, and by how much
1. Yes, especially in the city. But on the highway the 04 WRX gets only 1 mpg less than my 98 RS. My RS cruises at about 500rpms higher than the WRX and still gets better mileage.
2. Increasing compression ratio raises the Engines Thermal Efficiency. IIRC it continues to increase until a 19:1 compression ratio. There was a graph inside one of the E85 threads from the EPA that showed this. Raising thermal efficiency means more of fuel gets turned to motion instead of just heat.
The RS should always get better fuel mileage than the turbo models, mostly because of compression ratio.