I was getting 47-49 with Exxon. From the posts here I decided to try Shell. I put in a bottle of carburator cleaner (for the first time in 35,000miles) and a full tank of Shell. I see 43.6 mpg from Shell. Also interesting is that the gas indicator shows 7 bars down at 213 miles. I don't understand that! Shouldn't it be more like 4 or 5 bars down? Of Shell, it will take more to impress me. I'm going back to Exxon as soon as I empty this tank.
Gasoline is 'regional' so what I get in Huntsville AL is different from Birmingham or Nashville. Birmingham has all 10% ethanol. Nashville I can't tell but they also have ethanol. But Huntsville is straight gas from all local stations. East Coast gas is going to be imported from the Middle East and South America. Southern gas is going to be the Gulf of Mexico and South America. California is going to have Alaska and Middle East feedstock. The Mid West is going to have Canadian. Each feedstock is going to have a slightly different mix of organics and then there is the ethanol blends. But still, you have to go with what you can buy. My recommendation is to consider adding instrumentation so you can do a brake specific fuel consumption study. For this you'll need engine torque and RPM and mass airflow or injector timing. This will let you measure how much power you are getting for each unit of fuel. This takes out all of the environmental issues such as rolling and aerodynamic drag. I've done this with my NHW11 using Huntsville fuel from two years ago. I'll stick with Shell, Exxon or Chevron. I don't care for Texaco, BP, Citgo or other brands. If you are interested in the mechanics, we can go over it. Bob Wilson
I stay away from Shell. Too many of the things I have say in the owner's manual "do not use Shell gasoline, the additives are not good for this mechanism." So I just don't buy it for anything, not even the car.
You do realise the Prius does not have a carburetor don't you? Also you should take a look at Top Tier Gasoline. Exxon is not a Top Tier gasoline, but Shell is.
I don't have a Prius, but I've almost used Shell gasoline exclusively for my last 2 cars and my wife's last 2 cars and have had really no problem with anything that might be related to fuel quality. And I've pretty much run the gamut of cars with them - import & domestic, V4 and V8, luxury & piece of crap...
