22mpg is a pritty good mpg. I usually top off at 21 on hwy and stay near 19 with mixed city/hwy driving. I've changed the plugs, wires, air filter, cleaned fuel injectors and checked tire pressure to be at 29.
From what I've read on other posts some people get close to 30 mpg...don't know what they're doing to get that.
To answer your question, the most I've gone with an orange light is 30 miles. I wonder whats the max it can go.