When I started this thread, I used the results of a trip before the Summer really cranked up.

Driving Northbound avg 39.8 (32.8 - 44.5) on regular, 39.1 (35.9 - 45.1) on premium. Total miles 1,881.

Driving Southbound avg 40.2(31.6 - 45.4) on regular, 39.3 (34.4 - 46.5) on premium. Total miles driven 1,912.

Since then I have continued to average about 37 around town in 50/50 freeway and surface street driving. The Summer mileage is with the A/C going every afternoon, so I can't complain.

I now have 24K on my '10 and am now using synthetic oil. I hope to have enough mileage on it by it's first birthday to make a more comprehensive report of mileage. The only fuels I have used are Shell regular and V-power.

2010 Taffetta White
Sport, 5 spd

 

you got any references for this? Sounds like double-talk to me.

If you burn regular grade gasoline in your car designed for regular fuel it will not "detune." This only occurs in cars that are designed for premium.

When leaded fuel disappeared (1970s) the cars did not have computers controlling electronic fuel injection. They did not have computers controlling timing. They did not have computers controlling variable valve timing. They didn't have variable valve timing. Combustion chambers were not efficient. Don't compare cars today with cars built 40 years ago.

And no, premium gasoline doesn't have more energy than regular. It may have less. Any differences are not meaningful. The energy content will vary more from batch to batch of premium than it will between premium and unleaded. The energy content is not what makes it premium fuel.

cite.
cite.
cite.
cite.
cite.
cite.
cite.
my favorite cite.

 

After reading the cites Steve244 posted (+ rep, great cites) I'm going with bp reg. bcuz of the lower ethanol content and see were the MPG goes. I've been using Exxon 93 for about 6 months and have been seeing 28-33 MPG. GD3 and have kept all fillups on "My Mile Marker.com" since 11/3/09 lowest 25.98 highest 36.63 (highway trip) average to date 29.8 mpg. I do have an ETC and hammer MzFiT a lot change oil & filter @ 3-4k. The only other thing is short ram intake. Used Amsoil then switched to Motorcraft syn blend @ 1/3 the price. Not noticable loss in mpg just a gain in greenbacks.
Drained trans @12k filled with Universal Amsoil and added a small cooler this summer.

 

[QUOTE=Steve244;898587]you got any references for this? Sounds like double-talk to me.

If you burn regular grade gasoline in your car designed for regular fuel it will not "detune." This only occurs in cars that are designed for premium.

When leaded fuel disappeared (1970s) the cars did not have computers controlling electronic fuel injection. They did not have computers controlling timing. They did not have computers controlling variable valve timing. They didn't have variable valve timing. Combustion chambers were not efficient. Don't compare cars today with cars built 40 years ago.

And no, premium gasoline doesn't have more energy than regular. It may have less. Any differences are not meaningful. The energy content will vary more from batch to batch of premium than it will between premium and unleaded. The energy content is not what makes it premium fuel.

ROCKETT BRAND RACING FUEL
Tech - Closed Loop
February 2009 Total Performance Solutions
Daytona Sensors LLC - Tech FAQ Engine Tuning
HIGH OCTANE UNLEADED FUEL COMPOSITIONS AND METHODS FOR INCREASING THE MAXIMUM TORQUE OUTPUT VALUE PRODUCED BURNING SAME - Patent application
Insiders Theory
How, EXACTLY, does the ECU work? - Toyota Tundra Forums : Tundra Solutions Forum

The ecu does adjust to what ever gas use use, Regular will work but that doesn't mean higher octane wont give you better mileage.
Every one thinks that because the mfg says you can use 87 or higher that you can only use 87, it only means that your car can run it but dont mean premium wont ever be needed. The government wants you to use regular, because premium is harder to make.

Ive been using regular in my car for two tanks and getting better mileage but thats because I am driving slower and using the scangauge to get better mileage. Ive already noticed that its retuning and mileage is going down, My average speed is 5 mph slower then running premium and the mileage is averaging 1 mpg higher and dropping. I will use 1 more tank of regular and with lower humidity's next week I expect my mileage to average 36 mpg.

Premium gas does have more energy and your car can take advantage of it. I see lots of people using regular complaining of carbon problems and very poor mileage in normal suburban driving. Based on a 12000 miles year of premium is not 150.00 dollars its more like 10.00 dollars the cost is less than 1 bottle of a good fuel injection cleaner. 12000/34 mpg=353 gallons *3 dollars regular=1059

12000/36.5 mpg=329 gallons*3.25 premium= 1069 difference 10.00dollars and using less gas.
I used my 3 year average on premium and use the car mfg numbers on highway. Savings could be more.
I dont believe those sites because there is no science behind it. and every car is different because of the way you drive.

 

Well, from my own experience with an older 1997 Mitsubishi Mirage and a 1999.5 Nissan Pathfinder.

I find that in their old age, using premium gas is better for some performance, which equates a little to better MPG (not per $ though).

The reason I think so... is because of the engine's "lower" ability to efficiently burn gas. That somehow, the 87 octane isn't burning at the right timing/pressure needed. In one of the cites and on wiki, it talks about older engines building up carbon deposits inside the engine that result in slightly higher than normal compression. That can cause lower octane to detonate prematurely.

Which, incidentally, would've been better solved with an actual engine cleaning. Oh, well. Too late for that.

BTW, Steve... at least one of your cites, contradicts others. The "Myth" about using regular gas in a car that requires premium.

 

I just want you guys to understand how a car works and to be able to make up your own minds. Use what you want but have a understanding that you have an option. If you have to use fuel injection cleaner then the damage to motor is already started. If regular has additives to prevent problems then why use fuel injector cleaner? It all depends on how you drive. If you drive all city for many miles you should take your car on the interstate to blow carbons deposits off the pistons once a week.

Any time the engine knocks even if you dont hear it, there is damage to the engine and any time a mfg says a little knock is OK trade in that car. Little pits of aluminium on pistons and valves holds more carbon deposits and becomes a glow plug and the engine is dying a slow death.

 

Premium does not have more energy. I'm not sure where this is coming from. Premium has a higher resistance of pre-detonation which means a high compression engine (which itself can produce more power because of the high compression) will need Premium to run properly. It's not the gas that gives the engine more power, it is the engine itself that has the power and has strict requirements in order to obtain that power. (Premium fuel) Many will say, what's the difference.... The diff? a high compression engine designed to run on premium can generate more power using premium. an Engine designed to run on regular will not have any benefit because the gas itself has no more energy than regular.

Fuel injector cleaner is useful for the super cheap fuels that do not contain additives. It's also mostly a placebo for many drivers who used to actually need it "back in the day" (who now use top tier fuels).

What people need to know is that it's not the grade of fuel that produces the power but the engine itself and using the correct grade of fuel aides in allowing the engine to produce the power.

~SB

 

Premium does have more energy because its denser, 2 things happen.
1. Less fuel is need so your car runs leaner. 3-4 percent mileage gain
That can be because less ethanol too. 1-2 percent mileage gain
2. No knock so your car runs in the most advanced settings. 4-5 percent mileage gain over the trip.

I agree the premium is more resistant to knock and thats the energy needed cool the pistons and make for a denser charge, raises the mechanical efficiency's hence better mileage and less stress on engine.

If all gas has the minimum additive (government required) in the gas then their is no need for fuel injection cleaner. If all gas is the same and there is no differences between regular and premium except for cost. I agree that top tier gas is what is needed but you cant have it both ways.

Premium gas in a Corvette, BMW is because 1. It runs cleaner. BMW 50000 deposit test,100000 miles test. 2. When nailed it goes to open loop and runs a 12.5 afr for max horsepower and the extra cooling, and faster burn characteristic of premium insure a clean engine with no knock.

The engine tunes itself to how you drive. But when knock is present it detunes car and gas mileage goes down. Knock is a misfire and more gas is used and the dirtier you motor gets.

 

Did you bother reading any of the links you provided? Either they have nothing to do with the topic or they are talking about non-factory tunes and/or high performance engines.

edit: I'm guilty of not reading your post carefully.

You said, "Ive been using regular in my car for two tanks and getting better mileage but thats because I am driving slower and using the scangauge to get better mileage. Ive already noticed that its retuning and mileage is going down, My average speed is 5 mph slower then running premium and the mileage is averaging 1 mpg higher and dropping."

How do you figure your average speed is 5mph slower?!!!!! (the smilies here just aren't appropriate for what I think about this statement.) Are you taking it to a track?!!!! And after two tanks your mileage is going back to what it was? Premium/regular has no effect on mileage (although there is some anecdotal evidence (note your own statement!) that premium can reduce mileage in cars designed for regular due to less efficient burning).

 

I'm not sure I see a conflict. The Car Guys say they don't think using regular in a car designed for premium will damage the car. They don't say it would be smart. What conflict are you referring to?

For the record, I have a forced induction GM LNF engine sitting on wheels in my garage that recommends premium. After flashing with a new tune (GM Performance Parts tune covered by factory warranty) it "requires" premium (they even made us put stickers inside the gas cap cover stating so). I'm not going to put regular in this car. But if I did, I suspect it would go into limp mode before any damage was done to the engine.

 

I wanted to save money and use regular gas, but I noticed that I slowed down to get better mileage and that the ecu was tuning back to a regular tune. So for me no savings. I put links to explain how ecu works, If you dont understand that then how do you know premium gas wont give better mileage. I was being cautious like every one else on this website, if you want to hammer me go ahead, Its good that you stand for something.

They are not talking about high performance tunes, they are explaining how a ecu works. If you want more horsepower just richen up the fuel trim to 12 to 1 fuel air and take out timing. You are missing the point.

 

I think you're ignoring the fact those links are talking about aftermarket tunes on high-performance engines.

I don't think anyone except Honda is aware the GE8's ecu mapping. You haven't provided any evidence of such.

The Fit is designed for regular gas. Running premium in it won't hurt it. There is zero evidence (including your own) to indicate that it helps.

edit: put your money where your mouth is: Assuming you have a manual, get it dyno'ed after a couple tanks of regular, and then after a couple tanks of premium. Until someone claiming the benefit of running premium on a Honda L15 does this and provides objective evidence, they're just blowing smoke.

 

I get 36-38 on regular and 40-42 on premium driving and average of 45 mph per scangauge. I got 42-48 mpg on scangauge in a high humidity atmosphere and an average of 40 mph average driving the same route for 10 years. Also I noticed that the car was in open loop and timing was not as high because the fuel trim was richen up. If your happy with the mileage your getting fine. I just love the scangauge it tells you what going on. It matches pretty close to fillup and old fashion mpg check.

 

You've stated, on two tanks of regular your mileage was higher. Now you're saying it wasn't? Which is it?

Instantaneous readings on your scanguage aren't any more useful than the mpg dash bar indicator for comparison purposes. It's only a way of giving feedback on how you the driver are doing at the moment.

Yes, as you've pointed out, your driving patterns and characteristics have an effect on MPG. We're in agreement on this. Unless you can separate these from the fuel variable (i.e. by having dyno runs performed by a professional) there is no way to objectively compare the benefits of running regular vs. premium.

No where, has anyone been able to show documented evidence of greater performance running premium fuel in a car designed for regular. If you have a link stating this simple fact, please share it. Quoting the passage that supports this as well as linking to it will help your case. Technobabble unrelated to economy cars in general and Honda L15A's specifically does not.

There is no dispute that running premium in a car designed for premium fuel gives better performance.

 

^^_^^ I'm still trying to understand that engine and have little 'info' sourced material. Honda puts out scant little.

 

Scangauge gives a trip readout and tank readout so you can compare it also shows average mpg, speed and engine temp. Economy on premium is based on how you drive, because it makes the engine run more efficient you change the way you drive.

GD3 Honda Fit Jazz VTEC Full Review

This is the same car. 2007-2008 Honda fit.

I especially like this quote
The Jazz 1.5VTEC seems to have a habit of giving me surprises after surprises. Most certainly not as controversial as the timed performance tests of course, the Jazz VTEC also impressed me with its fuel economy under general driving conditions and indeed often shocked me by the excellent fuel economy I could get out of it under ideal conditions. The Jazz VTEC owners manual stipulated RON95 fuel as the minimum required fuel. Here in Malaysia, we generally have RON91 and RON97 fuel available at the stations, with Shell's 'V-Power' unofficially rated at RON98 (this fuel is not rated at the pump). So for the Jazz VTEC, I used RON97 fuel of course. For fuel economy measurement, I rely exclusively on the computer readout as this would be what owners will be using anyway.

At one time or another, most of us have probably been approached by friends asking about heavy fuel consumption on their cars, be it Honda or other makes. More likely than not, we would have told them that it all really depends on how heavy their right foot is on the throttle. For the Jazz 1.5VTEC, this adage holds more true than ever before. Under general driving conditions, with generally smooth moving traffic, occasional heavy traffic or slight congestion and under what might be caledl a "typical enthusiast's driving habits" : periods of light throttle cruising punctuated by frequent heavy or WOT spurts to overtake or simply to distance away from other cars on the road, perhaps an annoying tail-gater, or that heavy vehicle which seems to be slowing squeezing itself onto our lane. Under this kind of conditions and driving style, the Jazz 1.5VTEC can return between 12 to 14 km/litre, yes even with occasional, say 10 to 20% of time spent in slow moving heavy traffic conditions or even light traffic jams.

But exercise restraint and practise driving with a very light right foot and the Jazz VTEC will return amazing fuel economy levels. In one case, after topping up to a full tank, I first enter into slow moving traffic. The fuel consumption read-out started with 14l/km, eventually leveling out to 9.0l/km as the traffic slowly and painful stutters through a traffic light. Clearing this bottleneck, I entered onto a free flowing 4 lane highway, then uphill onto a 3lane highway, all the while with light traffic. I ended the journey, approximately 18km long with the fuel meter reading 5.5l/km or 18.2km/l ! My typical speed was around 80 - 90kph and I was even overtaking slower moving vehicles and the journey includes that period of getting stuck with the congestion at the traffic lights and also the cautious journey through a multi-storied basement car-park.

On the return journey, leaving the computer readout at 5.5l/km, I made my way back with the meter only going up to 5.9l/km (17km/l). This return journey involved going through a lot of uphill roads and getting stuck in a slow moving traffic jam. It also included a short period of WOT to out-drag a Perodua Kenari (another popular Malaysian made K-car) trying to cut me off, getting stuck for a while behind a tow-truck towing an E36 BMW 3-series and finally two rounds around the block looking for a parking space. In both journies, throttle position was very light, probably 5% or so and with engine revs hardly ever much above 2,000rpm except for that short period of madness outdragging the Kenari K-car. And even with such light throttle positions, speeds of 70 - 90 kph are easily reached. Good patience is of course needed since pickup is definitely going to be lack-lustre with so light a throttle position.

Honda officially rates the Fit/Jazz 1.5VTEC for a fuel economy of 20.0km/l (or 5.0l/km) for the 10.15 mode. As might be expected, this figure become an obsession for me during the fuel economy phase of the test-drive. I was obsessed with acheiving this same level of fuel economy, eventhough I know it to be a tough task since the official figure have probably been achieved under ideal test conditions on an empty test-track without traffic, conditions which are definitely not available on public roads ! Nevertheless, I was shocked that not only was I able to acheive 5.0l/km on the fuel computer, I was actually able to better this level during my test !

The 'all out' fuel economy test phase I conducted was during a week-day morning. After topping up to full tank at a Shell station, I made my way through a short stretch of city road to the North-South highway toll-gate, a journey of 11km with relatively heavy traffic (many are still driving to work) and with speeds of around 70-80kph. I stayed in the middle lane as most cars there were going this speed, with only occasional 'excursions' to the rightmost lane to overtake. The average consumption for this portion of the journey ? An amazing 4.8l/km appeared on the computer readout. That's 20.8km/l !

For the next stage of the journey, from the entry toll to the exit toll, a journey of around 7 km, i.e. all highway travel where traffic is now only moderate and of course speed and throttle positions are constant, the overall accumulate fuel consumption dropped even further, to only 4.5l/km or 22.2km/l. Average speeds were around 60 - 70kph and I stayed mostly in the leftmost, slow lane as the cars in the middle lane were going around 90 - 100kph since speed limit was 90kph. This journey ended at the exit toll gate queue where I waited for maybe 3-4 minutes and watch the overall consumption go back up to 5.0l/km or 20.0 km/l. So, it is actually quite possible to acheive the rated fuel economy for the Jazz 1.5VTEC even on public roads and under quite less than ideal conditions too !

 

2nd Gen Honda Jazz i-VTEC Test Drive Here is a review of the 209-2010 Fit

 

nice articles, but they have no information, opinions or otherwise, to support using premium fuel when regular is all that's required.

 

Agreed. Since fuel is used for the energy it produces and premium does not produce any more energy than regular, I still do not see where using premium fuel in an engine designed for regular will improve anything.

~SB

 

I am back to once again quoting my owners manual that states that fuel with an octane rating of less than 87 will harm your engine and is not to be used.... Nowhere have I seen in print from any Honda literature that the Fit is tuned specifically for the use of 87 octane fuel.... The ECU advances timing to a setting just short of pinging and with regular fuel about 25 degrees , premium fuel shows ignition advance under the same driving conditions 10 degrees higher on average.... Using octane booster I have seen ignition advance as high as 49 degrees dropping to as low as 10 degrees at full boost at 4500 RPM and increasing as the A/F ratio becomes richer as the revs climb...... What this proves is that the ECU is constantly making adjustments to make the absolute best fuel mileage possible for the grade of fuel being used and still maintaining a margin of safety too prevent damage being done to the engine.... If there is a problem where the ignition advance remains at a higher level than is safe for low octane fuel there is going to be a costly problem in time where this wouldn't be the case if higher octane fuel is being used.