Reg versus Premium Fuel experiament in 09 PT Cruiser
in [Cars]
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From: jim on 2 Nov 2009 13:07 "Dave C." wrote: > > > > that is why running hi-test in a car designed to use regular is a > > > waste of money. > > > > It may or may not be a waste of money (the only way to find > > out for sure is to try it). The EPA specifies higher octane fuel for > > its fuel economy tests - so it would stand to reason that some cars > > designed for regular fuel would get slightly better mileage with > > increased octane. > > > > -jim > > You've got that exactly backwards. Octane is a measure of the fuel's > resistance to pre-ignition (knock). This means higher octane fuel > doesn't burn as easily. Octane is measured by experimentation with a standard test engine ( incidentally, that standard engine was designed in 1909). It has nothing to do with burning easily (whatever you imagine that to mean). Hydrogen and methane seem to burn plenty easily as far as I can tell. How easily do kerosene and diesel fuel burn?. Which of those fuels has higher octane rating? > Thus, if you put high octane fuel in a car > designed to run on regular (like U.S. 87) then your fuel economy is > likely to DECREASE slightly. That is your belief... > > While this isn't technically correct, you could think of high octane > fuel as having less potential energy. I could think that if I wanted to be wrong some of the time. > The reason high octane fuel does > OK (mileage wise) in a car designed to used high octane fuel is that > high octane engines tend to be high compression. Thus, the engine gets > more energy out of the fuel. The EPA Fuel economy test uses 91 octane fuel. For a few years after the Car manufacturers started using knock sensors the EPA considered an administrative rule that a manufacturer could not make an engine that which got better mileage on 91 octane if the manufacturers recommendation for the car was to use regular fuel. This was because it was understood by everyone that with the presence of a knock sensor the engine management system could now be designed to learn to accommodate to the fuel octane. After some debate about whether the EPA should be requiring auto-makers to derate the potential gas mileage of their engines, they quietly dropped the idea. The current EPA policy on whether regular rated engines get better mileage on premium fuel is 'don't ask don't tell'. The EPA and the engine designers do not hold the same beliefs you do. There is a significant financial incentive for car manufacturers to design engines that get better mileage on 91 octane than they do on regular gasoline. -jim
From: Jim Yanik on 2 Nov 2009 16:22 jim <".sjedgingN0sp"@m(a)mwt.net> wrote in news:a9-dnWF4j890gnLXnZ2dnUVZ_gSdnZ2d(a)bright.net: > > > "Dave C." wrote: >> >> > > that is why running hi-test in a car designed to use regular is a >> > > waste of money. >> > >> > It may or may not be a waste of money (the only way to find >> > out for sure is to try it). The EPA specifies higher octane fuel >> > for its fuel economy tests - so it would stand to reason that some >> > cars designed for regular fuel would get slightly better mileage >> > with increased octane. >> > >> > -jim >> >> You've got that exactly backwards. Octane is a measure of the fuel's >> resistance to pre-ignition (knock). This means higher octane fuel >> doesn't burn as easily. > > Octane is measured by experimentation with a standard test engine ( > incidentally, that standard engine was designed in 1909). > It has nothing to do with burning easily (whatever you imagine > that to mean). the above is wrong. octane is a measure of a fuel's ignition characteristics. http://en.wikipedia.org/wiki/Octane_rating from answers.com; octane number n. A numerical representation of the antiknock properties of motor fuel, compared with a standard reference fuel, such as isooctane, > Hydrogen and methane seem to burn plenty easily as far as I can tell. > How easily do kerosene and diesel fuel burn?. Which of those fuels has > higher octane rating? > >> Thus, if you put high octane fuel in a car >> designed to run on regular (like U.S. 87) then your fuel economy is >> likely to DECREASE slightly. > > That is your belief... > > >> >> While this isn't technically correct, you could think of high octane >> fuel as having less potential energy. > > I could think that if I wanted to be wrong some of the time. > > >> The reason high octane fuel does >> OK (mileage wise) in a car designed to used high octane fuel is that >> high octane engines tend to be high compression. Thus, the engine >> gets more energy out of the fuel. > > > > The EPA Fuel economy test uses 91 octane fuel. For a few years > after the Car > manufacturers started using knock sensors the EPA considered an > administrative rule that a manufacturer could not make an engine that > which got better mileage on 91 octane if the manufacturers > recommendation for the car was to use regular fuel. This was because > it was understood by everyone that with the presence of a knock sensor > the engine management system could now be designed to learn to > accommodate to the fuel octane. After some debate about whether the > EPA should be requiring auto-makers to derate the potential gas > mileage of their engines, they quietly dropped the idea. The current > EPA policy on whether regular rated engines get better mileage on > premium fuel is 'don't ask don't tell'. > The EPA and the engine designers do not hold the same beliefs you do. > There is > a significant financial incentive for car manufacturers to design > engines that get better mileage on 91 octane than they do on regular > gasoline. > > -jim > Oh? What is that "financial incentive"? cites,please. It seems to me that manufacturers have a greater financial incentive to design cars for regular grade fuel. would you get enough of a mileage increase using premium to offset the added cost of premium fuel? -- Jim Yanik jyanik at localnet dot com
From: jim on 2 Nov 2009 19:42 Jim Yanik wrote: > > jim <".sjedgingN0sp"@m(a)mwt.net> wrote in > news:a9-dnWF4j890gnLXnZ2dnUVZ_gSdnZ2d(a)bright.net: > > > > > > > "Dave C." wrote: > >> > >> > > that is why running hi-test in a car designed to use regular is a > >> > > waste of money. > >> > > >> > It may or may not be a waste of money (the only way to find > >> > out for sure is to try it). The EPA specifies higher octane fuel > >> > for its fuel economy tests - so it would stand to reason that some > >> > cars designed for regular fuel would get slightly better mileage > >> > with increased octane. > >> > > >> > -jim > >> > >> You've got that exactly backwards. Octane is a measure of the fuel's > >> resistance to pre-ignition (knock). This means higher octane fuel > >> doesn't burn as easily. > > > > Octane is measured by experimentation with a standard test engine ( > > incidentally, that standard engine was designed in 1909). > > > It has nothing to do with burning easily (whatever you imagine > > that to mean). > > the above is wrong. octane is a measure of a fuel's ignition > characteristics. > http://en.wikipedia.org/wiki/Octane_rating That article in the wikipedia was written by an ignorant amateur. The length of stroke has nothing to do with compression ratio of an engine. There are high and low compression versions of the same engine (in case you don't know what that means - they both have the same stroke length). And there is no direct relation ship between how fast a fuel burns and detonation. Hydrogen burns faster than gasoline (the combustion spreads faster), yet it also has a much higher octane rating. > > from answers.com; > octane number n. A numerical representation of the antiknock properties of > motor fuel, compared with a standard reference fuel, such as isooctane, Yeah, so how does that statement support your mistaken beliefs? > > > Hydrogen and methane seem to burn plenty easily as far as I can tell. > > How easily do kerosene and diesel fuel burn?. Which of those fuels has > > higher octane rating? > > > >> Thus, if you put high octane fuel in a car > >> designed to run on regular (like U.S. 87) then your fuel economy is > >> likely to DECREASE slightly. > > > > That is your belief... > > > > > >> > >> While this isn't technically correct, you could think of high octane > >> fuel as having less potential energy. > > > > I could think that if I wanted to be wrong some of the time. > > > > > >> The reason high octane fuel does > >> OK (mileage wise) in a car designed to used high octane fuel is that > >> high octane engines tend to be high compression. Thus, the engine > >> gets more energy out of the fuel. > > > > > > > > The EPA Fuel economy test uses 91 octane fuel. For a few years > > after the Car > > manufacturers started using knock sensors the EPA considered an > > administrative rule that a manufacturer could not make an engine that > > which got better mileage on 91 octane if the manufacturers > > recommendation for the car was to use regular fuel. This was because > > it was understood by everyone that with the presence of a knock sensor > > the engine management system could now be designed to learn to > > accommodate to the fuel octane. After some debate about whether the > > EPA should be requiring auto-makers to derate the potential gas > > mileage of their engines, they quietly dropped the idea. The current > > EPA policy on whether regular rated engines get better mileage on > > premium fuel is 'don't ask don't tell'. > > The EPA and the engine designers do not hold the same beliefs you do. > > > There is > > a significant financial incentive for car manufacturers to design > > engines that get better mileage on 91 octane than they do on regular > > gasoline. > > > > -jim > > > > Oh? What is that "financial incentive"? cites,please. Did you just crawl out of the cardboard box you have been living in the last 40 years? You want me to prove to you that the car manufacturers have a financial stake in the fuel economy numbers they put on every new car they sell? Do your own research. > > It seems to me that manufacturers have a greater financial incentive to > design cars for regular grade fuel. > > would you get enough of a mileage increase using premium to offset the > added cost of premium fuel? I didn't say you will get any better mileage. Some cars do some don't. One things for sure - You won't find out if your car does get better mileage by asking on usenet. -jim
From: Ashton Crusher on 2 Nov 2009 22:51 On Mon, 2 Nov 2009 14:25:56 +0000 (UTC), Brent <tetraethylleadREMOVETHIS(a)yahoo.com> wrote: >On 2009-11-02, C. E. White <cewhite3(a)removemindspring.com> wrote: >> >> "Brent" <tetraethylleadREMOVETHIS(a)yahoo.com> wrote in message >> news:hclgpn$tpt$1(a)news.eternal-september.org... >>> On 2009-11-02, Ashton Crusher <demi(a)moore.net> wrote: >>>> I have pretty much gotten a decent feel for the gas mileage to >>>> expect >>>> from my PT. The last three tanks averaged about 23 mpg. So when I >>>> filled up yesterday I put premium in it instead of regular. It's >>>> too >>>> early for a definitive answer but so far it looks like it's down 2 >>>> mpg >>>> over what I'd been getting. About what I expected but I thought >>>> I'd >>>> test it out. >>> >>> It should be down a little. Premium has less energy per unit volume. >> >> That used to be true (say 30 years ago), but these days it is not >> ture. > >If higher octane ratings are achieved through oxygenates it certainly >will be lower because those high octane oxygenates have less >energy/volume. I think it is highly unlikely that higher octane ratings >would be achieved through aromatics these days for fuels one can buy at >regular gas station. > >http://www.epa.gov/oms/rfgecon.htm >http://books.google.com/books?id=J_AkNu-Y1wQC&pg=PA72&lpg=PA72&dq=energy+content+of+gasolines&source=bl&ots=j-Dw6PAVcq&sig=ZQI4tXkW_YZMjLf2epOMuDAA3OE&hl=en&ei=TeruSs7BOIuQMefywIQM&sa=X&oi=book_result&ct=result&resnum=10&ved=0CCcQ6AEwCTgK#v=onepage&q=energy%20content%20of%20gasolines&f=false > That's what I was thinking. I wonder how much alcohol they are allowed to put in basic gasoline. Maybe the main difference between regular and premium these days is the amount of alcohol they put in it.
From: Ashton Crusher on 2 Nov 2009 22:56
On Mon, 02 Nov 2009 10:25:45 -0500, elmer <e(a)f.udd> wrote: >Brent wrote: >> On 2009-11-02, Ashton Crusher <demi(a)moore.net> wrote: >>> I have pretty much gotten a decent feel for the gas mileage to expect >>> from my PT. The last three tanks averaged about 23 mpg. So when I >>> filled up yesterday I put premium in it instead of regular. It's too >>> early for a definitive answer but so far it looks like it's down 2 mpg >>> over what I'd been getting. About what I expected but I thought I'd >>> test it out. >> >> It should be down a little. Premium has less energy per unit volume. >> >High Octane has the same energy. It has a higher OCTANE and is wasted or >may not be burned as completly in a low compression motor or with >retarded or less advance in the timing of ignition. It burns slower and >does not detonate under heat of compression as easily as regular. >Fuel that uses more ethanol to increase octane has less energy. Regular >fuel with ethanol has less energy. >A 12 to 1 compression or even 14 to 1 compression motor burning 105 >octane or higher will get better mileage and torque if the ignition >curve etc are right. >Just like diesel the motor has to be built for the stress. >What we have now and for a long time is junk engines designed to be >built as cheaply as possible and to run on junk fuel as per EPA or >California really. The electronics are good at getting the most from >junk. Just imagine what great engine structure and electronics would do >with great fuel. I don't understand you claims of "junk" engines. Today's engines are far better in pretty much every way then everything that came before them including durability. That's a general statement, there will always be a few bad designs. Up until the mid/late sixties, engines were so weak that it was common for them to need valve jobs before 100K and for many of them they needed both rings and valves before that point. There used to be a thriving industry doing ring and valve jobs there was such a demand for it. |