um... i can add there were EXTENSIVE IDLE times. It was only recently that I finally stopped idling my car at customers' places (sometime in the spring). Though it's kinda difficult when summers (and winters) reach their "peaks."

As while I walked the food to the door, the engine was still running... and some of these customers were bit... um, time consuming. Despite having told the food total over the phone, they waited until I got there to LOOK for money.

And during the first year (all the regular gas and some premium), I took a LOT of "little trips," where I would pick a direction and explore for a few hours (and used those to raise my mpg). I pretty much stopped, since there wasn't as much new stuff to see without going much further and taking too much time (I was doing these after getting out of work 9/10pm).

edit: um... where did the 0.55 come from?

Ignoring my road trip (since that raised my premium mpg average by about 2 mpg)... my regular mpg average is 29.68 and at the start of the road trip, my premium is 30.48... making the difference 0.80 mpg (road trip "start" was the last pump before heading out of the city).

one of these days, I'll add more data since I still track my receipts. In the interim, I reset ultragauge after my road trip, and it's reporting a lifetime average of 31.2 mpg, it actually went up from 30.7 when I stopped idling so much.

While it's true that my regular pumps were only for about 7 months... about 2 weeks after starting to pump premium, I installed Swifts and then, about 6 weeks after that, I got my flat dunlop, which was when I switched over to 205/50/16 Continental DWS tires. Some folks claim wider tires lose mpg and some claim otherwise, so who knows.

I'd say... pretty good on premium, considering.

 

Beats the hell out of me... I get 0.42mpg difference between premium and regular checking it today...

11342 Miles travelled premium
375.996 gallons premium
30.16521452 mpg premium


8658 miles travelled regular
291.073 gallons regular
29.74511549 mpg regular

0.420099037 difference (premium mpg - regular mpg)

data



cool!

 

Sure it's anecdotal. It's also empirical. It's the only data set I've seen that carefully compiles the mpg using premium and regular for an individual car and driver for a large number of fills.

The standard deviation in mpg using premium is 1.99mpg. Using regular it's 1.64 (goober's data). A 0.5mpg difference isn't significant.

choosing outliers to prove a point?

What absurd absolutes? The only one I see is the insistence that premium fuel performs better than regular gas in terms of MPG in our Fits.

 

One I need to mention... by rearranging the lines... you're actually pulling wrong info... 3 of the premium pumps are actually regular gas... and two regular pumps are premium (the two lone premium pumps and regular pumps that directly follow need to be swapped and the very first premium after I stopped pumping regular, is regular gas).

You have to remember, the gas receipt indicates what type and how much gas was pumped, but the odometer reading is for all the fuel PRIOR to that pump... meaning if you look specifically at the two individual premium gas pumped in the sea of regulate gas. You'll only see how that tank of premium gas did by looking at the next line.

The formulas in the cells after the first four columns (my input columns), are all calculated and then in the columns that deal with total reg or premium they pull data from the next line. Notice the last line I put, the premium total is duplicated from the previous line because there is no next receipt inputted.

For all the data ending on 6/28/2011 as per your grouping, the numbers actually are:

Reg - 8941 miles on 301.214 gallons for 29.68 MPG
Prem - 11311 miles on 374.05 gallons for 30.24 MPG

Finally, a difference of 0.56 MPG (but there's a rounding issue with both MPG numbers, it's closer to 0.5567...).

Ding ding... found where the .55 came from.

 

Anyone notice a difference between using 10% ethanol gas and 100% pure gasoline? In my previous car ('03 Civic Hybrid) ethanol reduced my mileage by at least 3-4 mpg. Winter gas formulation also dropped me by 2-3 (regardless of ethanol content). My local station carries only non-ethanol gas year round, and that's what I always try to use. I don't like supporting the ethanol industry and the myth that it's somehow cleaner than gasoline. With hungry people in the world I can't justify burning corn in my car (yes, I know it's more complicated than that).

 

Having lived in a County where 10% ethanol has been required for about 20 years I have plenty of experience using the craponol "blended fuel. Luckily, the counties next to me are out of the Craponol required zones and the fuel terminal supplying those counties does not have Ethanol mixing capability. So I usually buy non-ethanol diluted fuel but also have accumulated data for both types across 5 different GM vehicles. I should mention I am on the road all the time. One of my regular clients is 158 miles away and I have some even farther.

The results are Craponol blended fuel gives me a consistent 11% loss in mileage. I also have the predictable loss in winter for the higher vapor pressure fuel but that is a separate issue.

As a side note the EPA dictates state what the vapor pressure should be by region. That number varies monthly with mid-winter being the worse and mid-summer be the best. There is actually less BTU's (energy) per gallon in mid-winter fuel vs. the best mid-summer fuel. When Craponol in mixed in they allow an additional 1 point vapor pressure variation.

Premium fuel "theoretically" should get no better mileage in the same vehicle if that vehicle is designed to use regular fuel. Regular fuel in the US is 87 to 85 octane (depending o the regional altitude) using the R+M/2 measurement method. Actually a very small amount of increase in mileage might be seen using premium because the engine computer can increase the timing advance to take advantage of the higher octane. That improvement could be in the 1-2% range.

There is another improvement others may see is in some states and provinces where ethanol is dictated for use for political reasons but not required as an oxygenate. Exceptions have been passed in a few states to allow premium fuels to be sold without ethanol added. Minnesota and Missouri are two example of this.

Here are some general BTU numbers without showing the differences for winter and summer.

1 gal of E0 gasoline =124,884 BTU
1 gal of E10 gasoline =120,096 BTU
1 gal of E85 gasoline =84,460 BTU
1 gal of E100 Ethanol =77,000 BTU

1 gal of No.2 diesel =138,874 BTU

 

Not sure where your getting your numbers from. RFG has about 111,000 BTUs and What is a Engine designed for regular gas? Premium is heavier so there is more BTUs per gallon which is about 2-3 percent. Then you have the advanced timing which is another 2-3 percent or more and that is not including the Knock retard which more mpg is lost. Its all about MBT timing which is tested at 91 r/m octane fuel.

I would agree on your premise of higher octane is not needed for a 8 to 1 compression motor but the compression ratio is 10.4 and more with carbon build up on all new Honda motors.

I just got a new Honda and hooked up the ultra gauge and my fuel trims are 2.34 for both and timing is -0.5 on regular at idle compared to my old Honda which was 8-9 degrees timing and -5.5 for both at idle with premium. Same motor designed for regular.

So as long as there is no knock my mpg should be 35 new car compared to 40 on premium of my old car under the same driving conditions.

 

I see no correlation between weight and energy available during combustion. You are correct that gasoline weighs 6.073 pounds per US gallon while ethanol weighs a little more at 6.584.

But the BTU content of gasoline is 124K while ethanol is only 77K. I think if you will check your owners manual they state that regular fuel is suggested. Most, not all, premium fuel get's it's higher octane rating by adding Ethanol, Prior to this using ethanol we got that octane boost by adding Tetra-ethyl (lead) . Octane is the resistance to auto-detonation In higher compression engines and has nothing to do with energy content.

Now we get into semantics on what is regular fuel. The biggest problem we run into is the measurement scale or method of the fuel you are using. In Japan the measurement method is RON while in the US the scale is RON+MON/2 (Also know as AKI). Since MON usually runs 8 to 10 points lower than RON, the number you see in the US and Canada is the average of RON and MON That average number (AKI) is 4 to 5 octane lower than RON for the same fuel.

So if your Japanese built and tested engine says use 91 Octane RON that equates to a US (and Canada) number of 86 to 87.

 

Except 98/99 RON and up is what is most common in Japan, and with out the MON you can't just pull the AKI equivalent out of your ass.

Octane is not a measure of resistance to detonation, and it is not a commentary on burn speed.

I can make two different combinations of petroleum based fuel with the same AKI, RON, MON whatever and they can burn at different speeds, require different range plugs etc.

Stop, you are looking silly.

 

I'm back after a long hiatus, and I get to come back to another one of these? Heck, 2 dumb discussions in the SAME thread. Wow.

I'll repeat it again: I've used 87 for a long time, and I've used 93 octane for a long time. I get better torque AND better mileage for MY driving style, because I take advantage of the better torque to stay in 5th gear. You can say whatever you like, but I bet y'all with the 87 or 85 octane fuel can't cruise all day at 25 MPH in 5th gear like I can. Just try it. I dare you.

The 10% ethanol claim is not much better, I'm afraid. You almost have a point if you're still using the 87 octane fuel, because it's not really 87 octane you're using. It's 81 or 83 octane, mixed with 114 octane ethanol. The chemicals in that stuff really are pretty crappy, compared with 100% 87 octane gasoline. 93 octane fuel with 10% ethanol will not have the low-grade crap in it, as it's more like an 87 octane fuel with some 114 octane ethanol. Unfortunately, the oxygenators in 100% 87 octane are more expensive, and some have been banned so you don't get cancer from your drinking water (MTBE), so you can have quality fuel, or cheap fuel.

Your 10% ethanol gas mileage claims are untrue, however, if you're comparing to quality fuel. I have run ethanol blends up to 70%. I haven't changed anything inside the engine, aside from routine valve clearance adjustments. My mileage difference is about 10% worse, but only if I use a whopping 30% ethanol or more. If you're getting 11% worse mileage, it's probably not because of the 10% ethanol, it's something else.

Great to be back.

 

I hate it when people can not carry on a decent conversation without trying to best the other person. I have more that a few years in the petroleum industry and I have have a few letters following my name defining my qualifications.

First this car is sold world wide, all be it, with three different engines for the various markets. Regular fuel is usually recognized as being 91 RON, mid range (called premium is some markets) is generally recognized as 93-95 and premium (super in some markets is 97-98. BP, Shell, and a few others do offer 100-102 in some markets.

The last time I was in Japan in 2008, Regular was 92 RON, Midrange was 95 RON, and Premium was available at 98 RON. In 1986 the Japanese set minimum standards. They are: Regular grade 89 RON, and "High octane" 96 RON. Those values are spelled out in JIS standard K 2202.

Looking at the international market for this car,

The last time I was in Australia (2007), they had 91, 95, and 98 RON. Also Shell was selling some ethanol "Blended" 100 RON fuel in Sydney, Brisbane, and Melborne. If I remember correctly it was 5% ethanol. I heard that offering went away a year or two after I was there.

New Zealand is 91 RON and 95 MON.

The Europeans have 91 RON in some countries with 95 and 98 almost everywhere.

In China almost everything is 93 RON.

Russia 92 RON and 95 RON

Saudi Arabia is 91 RON and 95 RON

I have no example for Africa as I was never involved with that market.

Years ago, before I got my advanced degree, I worked in a testing lab of a large oil company. We ran various engines and tested fuel against a standard of isooctane which is 100RON and 100MON. The RON standard was tested at 600 rpm with no load and a rich mixture. The MON value was tested at 900 RPM under load at a lean mixture. That results usually met the recognized difference of 9 or 10 between RON and MON.

If the results varied off of those values we had to reject the batch and use they used the fuel for something else. Besides random the batch testing we did, we were required to test everything going to aviation and military. RON/MON averaging (R+M/2) was not acceptable to them. As an example aviation regular that was labeled as 80/87 (dyed red and no longer available) or 100/115 (dyed green). This meant that those were the minimum numbers we had to see. The 80/87 usually came in at 82/90 While the 100/115 usually came in at 105/115 or a little better. Again while RON and MON separation are not always exactly the same spread, they are almost always 10 apart with an occasional drop to as low as 8.

So the MON numbers I gave you were from years of experience and internationally recognized numbers.

Rather than be antagonistic to other people's postings, I suggest that you read them and then decide for yourself if the information is of value to you. Trying to belittle another poster get's you nowhere. Others here can choose to use or not use the information provided.

I'm finished with this thread.

 

If I cruised all day at 25 I would get run over or run in by the cops, one of the two. Speed limit in front of my house is 40. At the end of my street it changes to 55.

The 11.1% figure is over 21 years, 8 vehicles (including my motorhome), 3 drivers, and 420,000 miles. The engine sizes vary between 1.5 and 7.3 liters. The summertime RVP is 9.0 in this area. Tell me what the problem is and I'll gladly go fix it. Oh by the way, The fuel around here is all supplied by BP no matter what brand you buy. The next county over is also supplied by the same BP refinery but it is shipped via pipeline to a different terminal that has no ethanol mixing facilities.

 

I thought you were finished with this thread?

That's just precious that you have some lab time with these fuels, that doesn't make you authoritative. I work with them in real world conditions on a week to week basis for the better part of a decade.

My clients live around the world. From Jacksonville to Johannesburg to Jakarta.

Data from varied climates and myriad platforms tells me more than the bench testing in school ever could have.

High load with lambda >1.0 at 600 and 900rpm are not exactly common values during operation in gas motors, let alone Hondas. It's really not an especially useful test other than it provides a benchmark to compare fuel. Octane is only a small part of the equation.

String out the pump gas in a 9:1 motor under 30psi boost turning through 9k rpm and you'll start to get a feel for whats actually going on in the combustion chamber when you've got a full standalone, thermocouples, a wideband, and pull the plugs after a good whack.

Or MTBE additives in a specialized Oxygenated E85 with 4 bar boost in a punched out high comp max effort big block V8 where you need to run an extra 10* advance over that pump gas in spite of the boost and compression because the bore sizes need it for a full burn and making your pressures peak at the optimum crank/rod angle.

/I have an Exxon refinery 40 miles from my house, they aren't the only ones delivering here however.

 

ok, so you are comparing 100percent 87 gas with e10 87. why don't you try comparing the 93 blends? that way, you have some kind of half decent fuel to compare with. if you have access to both 93 octane e10 and 93 octane e0, you'll be able to isolate the source of the mileage difference, if you care to do so. Otherwise, it will be impossible to tell if it's from the ethanol, or from the inferior fuel that has the ethanol which barely brings it up to 87.

 

All I know is that when I use my calculator and calculate miles/gallons, I get a bigger number when I use non-ethanol gasoline vs. 10%. Say what you will, but I'm fairly confident in my math skills. I buy gas (the real stuff) at the same station every time, so I'm satisfied that it's pretty much the same gas each time. When I did the comparison, I bought 10% ethanol wherever it was I happened to be on the road at the time. The mileage was always less when I burned it. Case closed as far as I'm concerned.

 

Ignorance is bliss. I just buy the cheapest gas, go vroom, vroom till i need some more and know that i'm doing better mpg wise than i would in a Truck..etc or most any car i've owned previously and not worry about it.
Gas prices are only going to go up n up, i don't see a point in getting all scientific about what fuel grade to use because you might as well get a hybrid or electric car and be done with it.

 

Welcome back, How is your e85 and premium doing? I thought maybe it died and you didn't want to talk about it?

I just got a new Honda Civic again after trying to get a Fit but because of no deals and people putting down the Fit, I decided to stay with the Civic. It has the Econ and with the ultra gauge it looks like a airplane cockpit. It says I am getting 44 mpg but I know that is wrong. 1/4 tank and 110 miles is more like 35 if I am lucky. The ultra gauge wont read a full tank like my other Civic. I also see positive fuel trims which with premium gas and the temps out side would be -5.5 for both with 8-9 degrees timing. On regular I see 3.56 long term and 6+ short fuel trims. Timing is -2 which is almost like a diesel. A car builds up cylinder pressure per degree in the range of 20psi to 40 psi and any thing faster is considered knock. On ECON the car wont get out of its way and without it I have to floor it for it to move.


Honda says timing should be 8 degrees at idle and with -2 it does not have the right fuel in it. I plan on running a few tanks of regular before bumping it up but I know what will happen. I might get OK mpg but it will fall as I put on miles until I change over. I also do not like the ecu adding fuel, every book and paper I have read about a properly running motor, fuel should be pulled out because engine damage can result.

 

Yeah, I'm not doing the e85 much anymore. I moved to another county last year, and they require you pass emissions. That means no CEL's, and it means the ECU must be all primped and proper and ready for the emissions test.

It took me almost a year of driving before the ECU was in the "ready" mode. I never could figure out why, but I stopped feeding it extra ethanol until it became "ready", then I got my emissions done. I did some E50 on my road trip to Chicago earlier this year, and the CEL came back as usual, but feeding it normal blends hasn't returned it to "ready" state.

I'm wondering if it's a fuel injector issue, but I consider it unlikely, since I'm averaging about 44 MPG with mild hypermiling. Timing is around 21 degrees at 80 load at my typical 2-3000 RPM. Still running 93 octane.

 

Oh, and I get about 12-15% worse mileage with E70 (9 gallons E85 mixed with 2.5 gallons 93 octane E10, if I remember right). Price per mile is within a dollar difference per tank, for ME, in my area.

@SilverBullet: Did you buy your Civic new? How many miles have you put on it? And, can you adjust the fuel tank size on the UltraGauge? What does your timing look like under load for 87 versus 93?

 

Wow you got it to 70 percent. I am impressed. Glad to know that.


I leased both cars new. Cheaper than buying new with all the miles I drive. The old '10 Civic had 34000 miles and needed tires and brakes plus all the filters and trans service. If I bought it my payment would have been the same as new with warranty so now I have a '12 without a worry. I filled the '10 with regular before the ultra gauge so I dont have the fuel trims but the 1st tank was 36 and second regular was 35 then I went to mid-grade and it went up to 38 and then premium to 40 plus. The fuel trims were always -3.1 winter and -5.5 summer or lower to -10. Its the percentage of fuel being pulled from the stock maps. That is why I was surprised to see positive fuel trims and especially the timing difference with the '12.

Unless more fuel is added to protect the engine during break in. People think 87 is what Honda recommends, its just the lowest octane that can be used. They say timing should be 8 degrees but -2 is 10 degrees away from what I seen with premium.

I am seeing lower engine loads with the new car but that might be the ECON feature. The motor is a little different too. The old Civic was 10.5 compression and new 10.6 but the HP and Torque is the same so I think the cam is different to bleed off the extra pressure. My old car was quick and this new vehicle like I said wont get out of its own way. The instant mpg is 20 percent lower too 50mpg compared to 60. Mpg is a average of all operating and temp. conditions. So its always changing and I have found its all easier to get repeatable mpg with premium. Right now I am in ECON mode trying to save money because gas prices here is almost 5 dollars a gallon. In Chicago it already is 5.09 for premium.

My old '08 Fit got better mpg in the winter and had the same mpg average as the '10.