I understand your GD is supercharged. Are you running an aftermarket tune as well?

While I don't expect you to run comparisons now using regular fuel, I hope ItstheWoo continues his.

 

PLEASE STOP QUOTING STEVE!!! He's on my ignore list, which means I don't want to read his drivel.

Arigatou gozaimasu.

 

Give it a try Steve - you might just experience a difference.

 

I think my bias against the use of premium where it's not recommended/required might bias the results.

If you or anyone could provide a published article that states there is an advantage to using premium where it's not recommended/required I might be persuaded to try it.

The whole internet is at your fingertips, this should be easy.

 

Steve, you remind me of a person that vehemently hates Chinese food based on what someone else said about it instead of having gone to the trouble of sitting down at a table and trying it himself.... "Follow the leaders, read the parking meters. People that think like you are why we will soon be a 3rd world country.

 

Reps to itsthewoo for switching to premium. Thanks to good people like tex and silver I made the switch and I will not go back to low grade.

Ever hear the saying you get what you pay for...gas is no exception!!!

I went to see my father today in the hospital, he is having open heart surgery on tuesday...keep him in your prayers. The hospital is 50 miles away. The way up I averaged 39.6 mpg going 70mph. On the way back I went 80 to 85mph and my average for the trip was 38.5 mpg. This is with the a/c on and doing some city driving. These are great numbers that I know from experience I could never realize using 87 octane.

I have kept records of every tank I have put in my fit and my mpg reading on the cars computer is very accurate.

@Itsthewoo, it may take several drives or several tanks for the ecu to fully adjust to the change in octane. You will at least break even using premium and your engine will run better and last longer.

 

Are you really comparing the technical aspects of running higher octane when it's not needed to getting take-out?

edit: answered my own question.

 

Are you really as clueless as you are portraying yourself to be?

 

KC, I'd say drive a steady 60 mph, reset the trip odometer, continue with cruise control on for 20 miles. Two similar cars, one with premium, one with regular. Both almost out of fuel... then fill them with the opposite fuel, make the same run.

Yes, I know, the computer has to learn, but it's the closest I can think of to scientific. Alas, you're a 3 hour drive away from me...

 

The computer won't know the difference unless you put a full throttle load on the engine a few times and let it rev beyond the VTEC transition so it will reset the ignition advance and air/fuel ratio to take advantage of the difference in octane.

 

I'm a former world-class rower and I'm over 4 feet tall- so I can easily push the accelerator all the way to the floor. I've done it before and I'll do it again.

But you're saying that otherwise the computer never tries to slightly push timing to see if it starts knocking (again)?

 

I'm feeling some of those subterranean blues right now.... The pump don’t work
’Cause the vandals took the handles.

Sound advice from experienced people who have an interest in sharing...

Where have all those flowers gone, long time ago???

 

Yeah, the ECU is constantly taking info from sensors and making adjustments as needed to optimize efficiency but if you don't jump down on it on occasion there is no reason for it to advance and relearn how much the ignition can be advanced... Advance adjustment is based on the knock, exhaust temperature sensor and intake (MAP, MAF, sensors... Since day one of owning my car I have gotten worse fuel mileage when shifting at very low RPM and not getting on the throttle at least once or twice when I first take off after the engine has reached operating temperature.

 

That's an awfully dumb computer- the car has a bad day, knocks a lot, retards timing and then it just sits there scared, never trying again to advance timing?

Fortunately I have to floor my car to 50 mph whenever I visit my parents because of one highway entrance. And I see them at least a couple of times a week.

 

Shaun, hook up the ultra gauge and watch you timing advance running regular. I run ultra93 when ever I can get it - 91 otherwise. I see the advance going beyond 50d. Would be interested in seeing what yours does. It's always a good idea to push an engine now and again.

 

Just deposited two nice checks this week, let me order the new toy and we'll see what happens.

 

My wife's Forester seems to do the same thing.. I don't drive it any where near as wound out as I do my Fit but I do let it rev up a bit before I shift and I do open the throttle at mid range revs. She gets a pretty consistent 25.5 MPG and I get close to 28 MPG when I drive it...

 

Premium helps low end torque and that is where the most engine load is. When your trying to get better mpg you want to keep the rpms as low as possible. I notice running premium that the car wont down shift and builds speed at low rpms so less gas is used too.

The knock sensor tells the ecu that there is no knock and allow the fuel trims to lean out.

I found a good paper to explain knock control with fuels. http://pid.sagepub.com/content/215/3/419.full.pdf

 

A bit off topic and anyone can answer, but since I've switched to a freer flowing exhaust, I've lost a bit of back pressure on the low end and tend to rev a bit higher on every gear to get up to speed, so would premium fuel help my MPG if I'm revving higher overall? I drive a 50/50 mix of freeway/suburbs and go about 65-75 on freeways.

 

Hope your dad is OK. I was wondering what was going on since the last time I talked to you. You are right on several tanks to get full effect but should notice the power improvement right away.