Originally Posted by salvadorik
When I see this the only word comes up to my mind - it really "sucks". Well below EPA estimates. I have the following: IS350 with 12K miles. about 50/50 highway/city. 19 Avg MPG
EPA estimates are based on putting the car on a dyno and simulating "typical driving" controlled conditions. It does not simulate "enthusiast" driving. In other words yes if you put a IS350 and a IS250 through the standard EPA test cases, you will see only about a 10 percent difference in MPG. However, most people that buy a IS350 want to use the extra horsepower -- the extra horsepower that does not really get utilized much during the EPA tests. So, in real world driving you might see a 20%-30% difference in MPG between the cars.
But it's not the car. It's the driver.
I've said it before here but it's worth saying it again. How you drive the car is the single biggest factor in your gas mileage. The EPA calculations are accurate in that they measure MPG in a controlled environment. Drivers who buy fast cars because they want punchy acceleration drive their cars differently than the car as its tested on the dynamometer for the EPA ratings.