Buy 100% gas. 10% ethanol added crap can drop almost 90 miles a tank compared to 100% gasoline.

 

No way.. even if it was 10% nothing gas, and I was only getting 90% of the energy I had from a full tank before, it'd only be a ~30 mile change on a tank.

I don't think there's anybody in my region that sells gas without ethanol anymore anyway

 

I'm fairly certain it's not a sticky brake caliper...at least my car hasn't been smoking or anything. I'm planning on doing a combination of changing my air filter, cleaning the throttle body, valve adjustment, and possibly also cleaning the fuel injectors. I'll probably also try to see if I can pull some codes that will provide some more info. Thanks for all the help guys!

 

I found a station in Nashville with no ethanol added. Just drove 290 miles back home on a full tank. With the 10% ethanol best I was doing was 200-230 on a full tank.

Ethanol has less btu's by volume than gasoline. Try a tank of gas with no ethanol added. You may be surprised.

 

mostly free moving. But there is some stop and go for a few minutes both in the morning and the afternoon.

 

that does explain a lot. Even if you're on city streets, if the lights are properly synched so you get all greens (or mostly) then you'd get much better mileage. At first, I thought something was wrong with my car/my driving when I was getting 20ish max, but I realized after doing everything (tune up, semi-hypermiling techniques, etc) that its most likely due to hawaii roads. Crappy traffic, up & down hills, etc.

 

Must be some factor other than the ethanol... Bad gas, evnironmental changes, something. I routinely get 280-290 miles per tank on the 10% ethanol stuff when I'm mostly on the highway. I know it has less energy, but it doesn't have *that* much less energy.

Like I said, theoretically even if the ethanol has absolutely zero energy (which obviously it doesn't), you should still only have a 10% drop in economy, nothing even close to the 20-30% drop that you experienced. In reality, I think the difference is somewhere in the range of a 2-4% change in energy density.

Not trying to be argumentative, I just don't want people to be unjustly afraid of 10% ethanol gas. 100% gasoline is definitely better, but only a tiny bit. Something else must have affected your car.

 

Just made the return trip... 25 mpg instead of 28mpg. Only change was the fuel.

 

Weird... Definitely a bigger difference than I would expect (not that 2 tanks is a very big data set). Guess it's time for me to find a 100% gasoline station near me, if they still exist, and see if I notice a difference. As much commuting as I do, I wouldn't mind another 3 mpg.

Edit: Just found this map of states/counties mandating RFG gasoline. I'm sure there are other areas where E10 is hard to avoid, but in the red areas of this map, it's mandated that E10 be sold, so you have no chance: http://www.epa.gov/otaq/rfg/whereyoulive.htm

It includes everything within a reasonable driving distance of me

 

It could definitely be this because the car is not tuned for oxygenated fuel from the factory. The fuel itself might have only a couple percent less energy density, but it all depends on how the car reads the A/F ratio, with oxygenated fuels the car might be getting confused "wheres this excess O2 that my sensor isnt reading coming from... " just an idea