More on Top Tier gasoline

"EdV" > wrote
>I hate to bring up the Direct injection thing again, but its related
> to top tier gas.
> True or False?
> Fuels without more detergents/cleaners wont affect a direct injection
> engine as much since the intake valves dont carry gasoline since the
> fuel is injected via nozzles.

As Elmo says, you've got to keep the injectors clean. Diesel engines
have major problems when the fuel is dirty, so I would expect similar
problems, although somewhat reduced due to gasoline's viscosity and
other problems.

However, I have seen a recent post on roadfly on the E90/92 forum
about at least one early 335i having trouble with deposit buildups on
their intake valves. Since gasoline is injected into the cylinder (rather
than intake manifold before the valves), and "bad" things are happening
as far as valve deposits:
http://forums.roadfly.com/forums/bmw...8991298-1.html
As with any anecdote, caution is in order, especially since this isn't
the first direct injection gasoline engine around.

FloydR

> "They fitted cameras to the inside of the combustion chambers"

Combustion chamber viewing was used for the last 100 years to assess
fuel quality. Sir Harry Ricardo was the first to play with it on a
single cylinder variable compression engine with a 1" thick optical
micah viewing port. Pre-ignition and detonation were seen as yellow
colored, and led the the quantification of gasoline's detonation
properties via the octane-heptane ratio.
Many gasoline test engines (variable compression, viewing port with
high speed cameras) are still in use in industry and academia, but are
somewhat obsolete with the introduction of ultra-fast pressure and
temperature sensors and computer modeling.
hth,
Ben

"Retired VIP" > wrote in message
news
> On Wed, 30 Jul 2008 18:09:05 -0400, "Mike Marlow"
> > wrote:
>
>>
>>"doug" > wrote in message
m...
>>>
>>>> wow, how uninformed can one person be.
>>>>
>>>>
>>> I wonder - just how uninformed are you? The 3.8 supercharged engine
>>> uses
>>> a knock sensor to vary engine operation - higher octane permits it to
>>> run
>>> at full optimization. Unless you have a foot of pure lead, this results
>>> in increased engine efficiency/fuel economy.
>>>
>>
>>Yeah - I know. But - real world experience... I owned a 3.8L Supercharged
>>Buick. I saw no significant difference in mileage or performance between
>>87
>>octane and high octane. The engine adjusts itself to the gas, and
>>optimizes
>>for what's in the tank. Granted - that will be somewhat lower for 87
>>octane
>>than for high octane, but I never saw enough of a difference to make a
>>difference. Don't know about the other poster Doug - but I'm informed.
>>Beyond what the spec sheet says.
>
> Today's cars don't tune themselves for better performance if you put
> in higher octane gas than they need. They have a default point of
> operation which is usually their most economical operating tune. Only
> if the fuel doesn't meet the engine's requirements does the computer
> de-tune the engine. It the engine is designed to run on 87 octane
> gas, the engine efficiency will be at it's best if you use 87 octane
> gas. You can burn 89 or 91 octane gas in a car designed for 87 with
> no drop in performance or mileage but there won't be any increase over
> what 87 octane provides.
>
> Octane is a measurement of how hard it is to catch the fuel on fire,
> not how much heat energy the fuel contains. The heat energy will be
> about the same in all grades of gas. If ethanol is used as the octane
> booster then 91 octane will have slightly less heat energy since
> ethanol contains about 30% less heat energy than gasoline.
>
> The octane requirement of an engine is determined by the engine's
> compression ratio, valve timing, ignition timing, fuel/air mixture,
> etc. The engine computer can control some of these in all engines but
> it can only de-tune to compensate for a fuel that doesn't meet the
> engine's requirements.
>
> A supercharged or turbocharged engine runs at an effectively higher
> compression ratio under boost than it's spec sheet ratio. Boost
> forces more fuel/air mixture into the engine which will raise the
> effective compression ratio. So a boosted engine will almost always
> require premium fuel.
>
> Jack

In the past, Ford claimed that the 5.4L V-8, which was intended to run on
regular fuel would have slightly higher fuel economy and slightly more power
if premium fuel was used. Their claim was a maximum improvement of around 3%
increase in fuel economy and maybe an extra 5 horsepower. I don't think must
people could reliably detect either change. I owned 2 Expeditions with the
5.4L V-8 and tried both regular and premium for extended periods and I never
could see any difference in mileage between the two. And there is no way I'd
ever be able to tell the difference between 265 hp and 270 hp just by
driving. I have also compared regular and premium in my Nissan Frontier
(4.0L V-6). Nissan says the truck is designed to run on regular fuel, but
that for maximum economy and performance premium should be used. The first
time I ran premium, the mileage records indicated a significant increase in
fuel economy, However, when I switched back to regular, the mileage stayed
the same. Since then I have tried premium for other extended periods, and
the mileage has not shown any improvement compared to regular.

One factor you guys don't seem to be considering is the effect of the
driver. Knock sensors adjust the engine parameters based on detecting knock.
The PCM doesn't know the type of fuel, only how the engine is reacting as
indicated by the presence of knock. What do you suppose happens in the case
of a driver who is very gentle and never provokes the engine to knock even
when running on regular? I am guessing it will adjust the engine parameters
in the same manner as if the engine was running premium. I suspect this
might be why some people claim significant difference when running premium,
while other (like me) see no difference.

Chevron used to have a really good set of web pages discussing gasoline.
Unfortunately they have replaced those with some advertising inspired
drivel. As I recall, the old Chevron pages addressed the question of energy
content of premium and regular. They claimed premium contained around 3%
more energy than regular on average, but that the energy content of gasoline
in general varied by around this same amount, so in some cases a particular
batch of premium might have less energy than a particular batch of regular.

At least in North Carolina, gasoline samples are routinely checked to verify
the octane.

The gasoline FAQ http://www.faqs.org/faqs/autos/gasoline-faq/part1/ is an
interesting, if not always accurate source of information on gasoline.

Regards,

Ed White

"C. E. White" > wrote
> "Retired VIP" > wrote
>> On Wed, 30 Jul 2008 18:09:05 -0400, "Mike Marlow" wrote:
>>>"doug" > wrote
> In the past, Ford claimed that the 5.4L V-8, which was intended to run on
> regular fuel would have slightly higher fuel economy and slightly more
> power if premium fuel was used. Their claim was a maximum improvement of
> around 3% increase in fuel economy and maybe an extra 5 horsepower. I
> don't think must people could reliably detect either change.

Yeah, I agree. There's a very nice article on Dinan's website about
dynonometer
testing that has a section on 93 vs. 91 octane fuels. They measured an 11
HP
(IIRC - can't get to their website right now) on an E46 M3 - but that's only
3%.
Important on the racetrack, but inconsequential in everyday driving, as 343
hp
is more than sufficient.

> One factor you guys don't seem to be considering is the effect of the
> driver. Knock sensors adjust the engine parameters based on detecting
> knock. The PCM doesn't know the type of fuel, only how the engine is
> reacting as indicated by the presence of knock. What do you suppose
> happens in the case of a driver who is very gentle and never provokes the
> engine to knock even when running on regular? I am guessing it will adjust
> the engine parameters in the same manner as if the engine was running
> premium. I suspect this might be why some people claim significant
> difference when running premium, while other (like me) see no difference.

I completely agree. Although it's likely that, in very well-controlled
experiments premium fuel may give someone with an engine designed
for high-octane fuels a little more mpg, in everyday driving you're not
likely to notice any differences. As I've mentioned in other sub-threads,
the effect on blends, especially of ethanol, is likely to be more
noticeable.

The faq gives some nice info on how closely experiments must be
controlled, particularly temperature. Also, I hadn't really considered the
fact that the high operating temperatures that BMW's are set up for also
increase the need to run them on premium, for max performance.

It's too bad that Jim won't read and believe the faq.

FloydR

On Jul 30, 7:51*am, "Mortimer" > wrote:
> "Retired VIP" > wrote in message
>
> ...
>
>
>
>
>
> > On Tue, 29 Jul 2008 21:17:58 -0700 (PDT),
> > wrote:
>
> >>On Jul 29, 7:13 am, "Elmo P. Shagnasty" >
> >>wrote:
> >>> In article >,
> >>> Fat Moe > wrote:
>
> >>> > As far as getting extra mileage with
> >>> > higher octane? I don't buy it,
>
> >>> Octane is not the issue. Cleanliness of the fuel injectors and intake
> >>> valves and combustion chambers is the issue.
> >>I've had my 98 Pontiac Grand Prix GTP for a little over ten years now,
> >>and follow the gas mileage carefully. Using 92 octane, I will get a
> >>full mile per gallon better than using mid-grade. Using 87 octane will
> >>cost me 3-4 mpg, so it costs me a LOT more by using the cheaper
> >>gasoline. The difference in acceleration is very noticeable as well.
>
> I'm interested that you say you get "a full mile per gallon better". That
> suggests that you normally get results which are consistent to within a
> fraction of an mpg, such that a difference between fuels is significantly
> greater than the difference between successive tank-fillings on the same
> fuel.
>

When I say "a full mile per gallon better ", I mean that driving under
the same type driving conditons, speed, weather, pay load, highway or
city, air conditoner use, etc if I drive the SAME way, I will get one
mile per gallon better on a consistent basis. Have done so for years.
Maybe not a noticeable difference, but the higher octane gasoline is
better for my particular automobile.


> My experience, with both petrol and diesel cars, is that the variation
> between one tank filling and another is about +/- 3 mpg, depending on
> factors such as the type of driving (mainly urban / mainly high-speed / some
> mixture of the two) and different points that different fuel pumps cut off
> when they sense that the tank is full.
>

Of course, if I am driving 85 on the interstate, I will get less
mileage than if I am cruising at 70 (which is the speed I usually use
to test my gas mileage), even less if I slow down to 65 or so.


> My figures are for filling the car to the pump cut-off point and then
> running it until the tank is fairly low - typically for fillings of about 50
> litres (11 gallons UK / 13.5 gallons US) and journeys of around 550-650
> miles.
>

I use my car's on board mileage calculator, which I have tested and
found to be extremely reliable.



> I've noticed a difference in the smoothness of the engine and the
> acceleration between supermarket diesel and BP Ultimate diesel, though some
> of this could be wishful thinking to compensate for the extra cost of BP
> Ultimate - when you pay gold-plated prices maybe your brain thinks it can
> see extra gold-plated performance!- Hide quoted text -
>


I feel the same way about using Shell's Premium. My car runs a little
better on it than on other brands. (At least I THINIK it does!)
> - Show quoted text -

The formerly named British Petroleum operates only Amoco and Arco in
the US. Not the top names or on the Tier 1 list. So I guess your shop
is probably right.

However, BP does have excellent lubrication products like Castrol oils
and the likes of GT Low Moisture Activity brake fluids. Maybe their
European gas is Tier 1 equivalent? Don't know.



On Jul 29, 9:59*am, "Elmo P. Shagnasty" >
wrote:
> That's hilarious, because the local lawnmower shop specifies NOT to use
> BP under any circumstances.
>
> This place has been around for 50 years, and they've said that for as
> long as I can remember.

"doug" ...
> After reviewing the list of TOP TIER Gasoline Retailers at their website,
> http://www.toptiergas.com/retailers.html , I couldn't help but notice that
> Valero, one of the largest independent refiners in the eastern US, was not
> on the list. Here in Delaware, the Valero refinery in Delaware City was
> built in the mid 1950's specifically designed to handle sour crude. It is
> still in operation, providing numerous retail operations in this region,
> including Shell (which IS on the list) with their gasoline.
>
> If suppliers like Turkey Hill Minit Markets and Qwik Trip are identified
> as being Top Tier gasolinr retailers, why isn't Valero? Especially if they
> are supplying gasoline to companies that ARE on the list?
>
It is all in the additive package added to the tanker truck
after/during/before the same base gas is transferred to the trick. Same
gas, different additives.

I, for one, am not convinced that this Top Tier stuff has any meaning at all
anyway.
Tomes