Re: More on Top Tier gasoline

"Retired VIP" <jackj.extradots.180@[EMAIL PROTECTED]
> wrote in message 
news:6bj0945krobtl9il2go8jqu933eun13q5n@[EMAIL PROTECTED]
> On Tue, 29 Jul 2008 21:17:58 -0700 (PDT), coachrose13@[EMAIL PROTECTED]
> wrote:
>
>>On Jul 29, 7:13 am, "Elmo P. Shagnasty" <el...@[EMAIL PROTECTED]
>
>>wrote:
>>> In article <488ef841$0$4014$bbae4...@[EMAIL PROTECTED]
>,
>>> Fat Moe <Fat...@[EMAIL PROTECTED]
> 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.

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.

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'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!