dmanwi

Has anyone experienced an increase in gas milage when moving down a grade? I was getting 15.9-16.5 MPG while on 92 octane and that has jumped up to 18MPG using a tank of 89 octane. Same outside temp, same driving routes.

mdbrown

Theoretically, there is more combustible fuel and fewer additives in lower grade gasoline that should increase mileage but it shouldn't be that drastic. It's possible that you switched over at about the same time your local stations switched from winter fuel to summer fuel although even both together really shouldn't make a difference that large.

mylexbaby

Is this based on the computer or actual calculation? And it might be due to differences in how full the tank was.

So maybe try a couple of more tanks and see if the difference stays. (Even if it doesn't, why do you need 92 octane? )

RedGemini

I'm thinking the tank I got last Saturday when I was out of town might be summer blend, as my average is sitting around 20 with a good chunk being highway, and it's 89 instead of my usual 91-93 I usually get.

chris948

Even if true, and that's not a given, that's nothing compared to the benefits of additional compression that you would get at a higher octane.

Measuring gas consumption that precisely is a fun thing to do for the internet, but in the real world, a joke. Your car being parked on an uneven piece of concrete while filling up, or how the gas pump shuts off automatically as it nears full is going to make a much bigger difference than the grade you chose in an uncontrolled environment. Way too many variables.

BlackLexRX

There's a huge debate thread about this on the 4th gen forum. You can read through it to see others experiences and lots of opinions, but in the end, just opinions and no empirical evidence that any grade of fuel is better. It's also widely accepted that using lower grade fuels isn't detrimental. Personally, I stick with what's in my manual, the 91 octane that the Toyota engineers prescribed for my RX350. I've ran a few other vehicles North of 200K by sticking with manufacturers specs too.