What are the effects of driving around in 4th between 2800- 3200 RPM on the highway instead of upshifting to 5th? I know it decrease gas mileage but does it decrease engine life?I just took a 1000 mile trip in the car and kept it in 4th over half of the trip. It sounds so sweet. I plan to make this a track- only car when I reach 40-50,000 miles. Thanks.