Is a 2010 Chevrolet Impala good on gas?

No, the 2010 Chevrolet Impala is not known for being good on gas. Its fuel economy is considered average to below average for its size and class. While the exact MPG will depend on the engine (there were a few options available that year), you're unlikely to see highway numbers much above 30 mpg and city numbers will be significantly lower. For comparison, many modern vehicles offer considerably better fuel efficiency.