Reg versus Premium Fuel experiament in 09 PT Cruiser

"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

jim > wrote in
:

>
>
> "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

Jim Yanik wrote:
>
> jim > wrote in
> :
>
> >
> >
> > "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

On Mon, 2 Nov 2009 14:25:56 +0000 (UTC), Brent
> wrote:

>On 2009-11-02, C. E. White > wrote:
>>
>> "Brent" > wrote in message
>> ...
>>> On 2009-11-02, 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.
>>>
>>> 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_A...olines&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.

On Mon, 02 Nov 2009 10:25:45 -0500, elmer > wrote:

>Brent wrote:
>> On 2009-11-02, 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.
>>
>> 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.

On Mon, 02 Nov 2009 08:16:06 -0600, Don Stauffer
> wrote:

>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).


My preliminary assessment is that it's down at least 2 mpg and
possibly as much as 3 or 4.

Ashton Crusher wrote:
>
>
> 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.

In our town, they can put up to 10% ethanol in the gas. I think it's
some kind of scam the state is taking part in but that's the brakes.
There is a slight drop in gas mileage but the good news is that I can
use the lowest grade of gas in my cars without knocking. Previously, the
cars had to use mid-grade.

Ashton Crusher wrote:

> ...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.

They also finally figured out how to and/or decided to make CV joint
boots that could generally last the life of the car. They had to
replace those recurring multi-hundred $$ maintenance needs with
something else. That's when some genius said "Hey! I've got it! Let's
start driving the cams with timing belts in almost every engine, *AND*
let's bury the water pump inside the engine and have it be driven by the
timing belt! And to really mess up a few people's bank accounts, let's
make those same engines with the cams driven by high-tech rubber bands
to be interference!!".

--
Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

Ashton Crusher wrote:
> On Mon, 02 Nov 2009 10:25:45 -0500, elmer > wrote:
>
>> Brent wrote:
>>> On 2009-11-02, 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.
>>> 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 befor
> that point. There used to be a thriving industry doing ring and valve
> jobs there was such a demand for it.
Remember the Hemi of the late 60s, not the mid sixties. It put out an
honest 800 hp and 860 ft lbs according to modern testing a year or so ago.
They came apart because that much power and trying to rev past 8000 rpm.
If you kept it at 7000 or below everytime it stayed together. However
the head block gasket would seep a little bit of oil, if constantly
stressed.
Name me one engine that puts out that torque that you can afford. I've
got one of the modern high hp jobs. It revs like crazy but hasn't got
any torque. Next time you get a chance ride in a 70 442 w 410 gears, or
a Hemi Cuda properly tuned. A 429 Cobra Jet or a 428 for that Matter, or
a high winding 427 or a bunch more.
The new engines don't come apart becaause they don't put out power that
will break them. you 3.3 mph per second regulated electronic throttle is
a wuse. A hemi with modern developments could probably push 900 hp.
Street Rod Standards are now in the 1000 hp range. Try that with a
Mercedes engine short of 6.3 twin turbo. None of them will survive.
The reason the don't run 186 mph or above is rear gearing and no
overdrives in the gearbox. A 440 or hemi and a number of others would do
155 at 8000 but don't expect it to live.
Ride in a 427 Vette and wish it had the gearing etc box of the new
Vette. The technology is far more developed today but it is not applied
but who "needs" a 250 mph 900-1000 hp Hemi.
The new Hemi is more a Polsphere head It has an unfinished area to hold
heat and twin plugs to burn junk fuel.

Ashton Crusher wrote:
>
> On Mon, 02 Nov 2009 10:25:45 -0500, elmer > wrote:
>
> >Brent wrote:
> >> On 2009-11-02, 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.
> >>
> >> 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.

But that has nothing to with the engine itself. To claim that burning
rings and valves is evidence of a "weak" engine is silly. That
definition would mean the weakest engines are the ones used in dragsters
and race cars.

Take a hundred of what you think are the best built car engines today
and install a breaker-point ignition and a carburetor on them and you'll
find out the rings and valves don't hold up as well as the cars that
were designed with those old fuel and ignition systems.

The point that I think was being made was that toady's manufacturers
and oil companies are delivering cheaper quality to the consumer, but
the electronics used today more than compensate for that.

-jim