Reg versus Premium Fuel experiament in 09 PT Cruiser
in [Cars]
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From: Don Stauffer on 2 Nov 2009 09:16 Ashton Crusher 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. I had a Neon RT. I did an extensive milage test early on. I did ten tankfuls of regular, then ten of premium, figuring the variance of each set. The milage with premium was down a little, but less than one mpg. However, the variance in each set of runs was over 1.5 mpg, so I had to conclude it made no difference. I think the Neon engine was very similar to that in the PT (though mine had the DOHC heads).
From: Brent on 2 Nov 2009 09:25 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
From: jim on 2 Nov 2009 09:45 Jim Yanik wrote: > > Bill Putney <bptn(a)kinez.net> wrote in > news:7l6qnpF3c67veU2(a)mid.individual.net: > > > Ashton Crusher 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. > > > > I don't know for sure, but there are those that would say that you have > > to give your PCM time to adjust to the different fuel to make a > > meaningful mileage measurement. > > > > if the motor is not knocking with regular fuel,then changing to hi-test > isn't going to make any difference.ECUs don't have any way of discerning > octane levels,and the O2 sensor will not read different for hi-test. Actually the computer does have a way of detecting octane - it is called the knock sensor. And the O2 sensor may read differently if the fuel oxygen content is different, which may or may not be the case depending on where you get the fuel. > > 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
From: Dave C. on 1 Nov 2009 22:26 > > 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. 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. While this isn't technically correct, you could think of high octane fuel as having less potential energy. 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. -Dave
From: elmer on 2 Nov 2009 10:25
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. |