Has anyone tried premium for better mileage?

[Klasse Act]

Having just gotten out of a 2010 Honda Fit sport w/5AT I'm used to good gas mileage. That car was "rated" at 27/33 w/ the 5AT but I never, ever got that, waaaay better. When it was pretty new I took back home to Detroit and got 36 mpg on the freeway. A couple trips after that I got 43 mpg coming back to Chicagoland. The route was the same along with how I drove too, right lane w/ the cruize on going 70 mph and only speeding to pass idiots that don't know how to drive on the freeway. Even after adding wider tires (205-50's) and 1" wider wheels the mileage stayed up and my last trip back home with the Fit, this past Labor Day weekend had me getting 43 mpg on the way home after filling up in Indiana and btw this was w/ the a/c on too.

Now that I've got that out of the way, I must say that I'm sold using premium in this little engine due to its high compression ratio. Yes I know its tuned to run on 87, fair enough but Honda doesn't say you CAN'T run 93 and hurt anything either, so I'm now trying it with the CR-Z, just filled it up for the first time today at my local BP ($4.25 a gallon)

When I first switched to premium the Fit was pulling down 22-23 mpg with mixed driving in the winter but when I switched to premium it went up within 2 tanks to 28-29 mpg. Now I will say that I had a K&N typhoon intake too which pulled in all that cold air and I'm sure the ECU dumped more fuel to compensate for it. About a month ago, when the summer heat started going away my mixed mileage was 38.8 mpg and in the middle of summer w/ the a/c blasting all the time would net me about 31.5-33.5 mpg on average.

So, has anyone tried premium for an extended period of time with good results? If noone has, I'll be chiming in with my results for sure, with this car its all about MPG and not MPH, right

[TinTin]

i was talking to some CRX people and they said that its the ethanol that kills our fuel economy. I usually look for stations that serve no ethanol/little ethanol in their fuel. The higher octane fuels have less and less amounts of ethanol in them. I feel like it helps get better economy. But in all honesty, i dont care about economy at all. I drive how i want and if the car needs a refuel it gets one when it needs it.

[Widget]

While I'm not going to attempt to refute the fact that you gained MPG when switching to premium on your previous vehicle - but it was probably more due to that special euphoric feeling you get when you add something new to your car and "WOW THIS IS SO MUCH BETTER!"

However, octane rating scientifically has literally nothing to do with your MPGs. In fact, it will literally make zero difference in the car's performance without drastically overhauling the car's tune. Your car's ECU does not magically realize that there is a higher octane fuel added into the car and starts pushing higher piston compression.
You can argue with the facts all you want - doesn't matter to me, however, the facts are facts.

You can read more about this on Wikipedia Octane rating - Wikipedia, the free encyclopedia

[Widget]

Originally Posted by TinTin

But in all honesty, i dont care about economy at all. I drive how i want and if the car needs a refuel it gets one when it needs it.

Even though it's completely off topic - I agree totally here.
Would've bought a Prius if I really wanted to pull high efficiency numbers.

Though, I do enjoy being able to drive around with a heavy foot throwing around WOT at every light and corner and looking down to 29-30 MPG average.

[MachVEvan]

The higher the octane rating, the more resistant to burning/detonation. With this in mind your fit only lost fuel economy for the first tank while the car was learning the new spark advance/retard strategy since it could change up the ignition sequence a bit to take advantage of the less volatile fuel mixture.

I don't trust that the CRZ would work the same, but it cant hurt the car. In fact, higher octane fuel can actually clean your engine/fuel system.

[Widget]

Originally Posted by MachVEvan

In fact, higher octane fuel can actually clean your engine/fuel system.

Hi, do you have any evidence or data backing this claim? I have not seen a single bit of information that supports this information.

Again, scientifically, higher octane has absolutely nothing to do with how clean the gasoline burns. It only makes a difference with compression ratio.

[Neutron256]

My wife and I have been testing this on both our Fit and the CR-Z. We see no noticeable difference in either car's MPG with Regular or Premium. That said, almost all the miles we put on are the worst kind of stop and go city driving.

Sometimes I think I feel a difference when accelerating hard, but it could easily just be my imagination.

[aerodan]

California gas is pretty bad due to ethanol, so I run 91 just to get less of it. I've noticed no difference. There's a station that sells 100 octane race gas here, but that's just silly unless someone wants to spot me a tank for a "scientific experiment" :-)

[andrewr]

I have only used 89 in my CRZ since I bought it, and my MPG blows the EPA numbers out of the water. Bone stock I can and have made many trips of 75-300 miles getting 45-52 MPG. A lot of things factor into MPG, but I am quite certain the CRZ loves 89 and probably higher octance gas both for performance and MPG, not to mention cleaner for the fuel system.
Ethanol in our gas sucks, big time. Google for gas stations around you that sell ethanol-free gas, your car will thank you. Also, keeping your tire's air pressure up helps a lot.

[YLA]

We have only 95 and 98 here in Europe (if these are the same meanings).
Al new cars use 95