Premium Gasoline

I recently purchased my first BMW -- a 1994 352i. I think it's a great
car. However, I notice that the owner's manual indicates that I should
fill my tank with high-octane ("premium" here in the United States)
gasoline. I've never before used premium gas, figuring that it was not
necessary and never previously having had a problem with regular (87
octane) unleaded with my other cars (mostly Volvos). Now, with the
price of gasoline reaching all-time highs here in the U.S., I want to
make quite sure that my "new" BMW really needs 89- or 92-octane
gasoline. Any perspectives on this issue would be much appreciated.
Thanks in advance.

Jeff Morris
Arlington, VA
USA

M y '94 352s (sic) get mid-grade gas.




> wrote in message
ups.com...
>I recently purchased my first BMW -- a 1994 352i. I think it's a great
> car. However, I notice that the owner's manual indicates that I should
> fill my tank with high-octane ("premium" here in the United States)
> gasoline. I've never before used premium gas, figuring that it was not
> necessary and never previously having had a problem with regular (87
> octane) unleaded with my other cars (mostly Volvos). Now, with the
> price of gasoline reaching all-time highs here in the U.S., I want to
> make quite sure that my "new" BMW really needs 89- or 92-octane
> gasoline. Any perspectives on this issue would be much appreciated.
> Thanks in advance.
>
> Jeff Morris
> Arlington, VA
> USA
>

> wrote
>I recently purchased my first BMW -- a 1994 352i. I think it's a great
> car. However, I notice that the owner's manual indicates that I should
> fill my tank with high-octane ("premium" here in the United States)
> gasoline. I've never before used premium gas, figuring that it was not
> necessary and never previously having had a problem with regular (87
> octane) unleaded with my other cars (mostly Volvos). Now, with the
> price of gasoline reaching all-time highs here in the U.S., I want to
> make quite sure that my "new" BMW really needs 89- or 92-octane
> gasoline. Any perspectives on this issue would be much appreciated.

There have been many discussions on this subject in this group,
and also IIRC in rec.autos.driving - you should google them.
Basic story is: you probably can use regular without engine damage.
You *will* get less power, as BMW engines are optimized for premium.

Given that, I'm not sure that the M50 engine in your car (I presume
you actually have a 2.5L not 5.2L engine ;->) has as *good* a set
of knock sensors and engine controller as the current crop of BMW
engines do: if your car pings *at all* on regular, move up to mid-grade
and then premium.

FloydR

On 24 Jun 2006 16:43:14 -0700, "
> wrote:

>I recently purchased my first BMW -- a 1994 352i. I think it's a great
>car. However, I notice that the owner's manual indicates that I should
>fill my tank with high-octane ("premium" here in the United States)
>gasoline. I've never before used premium gas, figuring that it was not
>necessary and never previously having had a problem with regular (87
>octane) unleaded with my other cars (mostly Volvos). Now, with the
>price of gasoline reaching all-time highs here in the U.S., I want to
>make quite sure that my "new" BMW really needs 89- or 92-octane
>gasoline. Any perspectives on this issue would be much appreciated.
>Thanks in advance.
>
>Jeff Morris
>Arlington, VA
>USA

Premium car = premium gas. If you don't want to, that's your
decision. The cost over time isn't really all that much, especially
when compared to out-of-warranty engine repairs.

"Toby" wrote
> Premium car = premium gas. If you don't want to, that's your
> decision. The cost over time isn't really all that much, especially
> when compared to out-of-warranty engine repairs.

Being a '94 model year, I doubt he still has warranty.

Besides, a knock sensor would most likely pull timing and not allow the
engine to get damaged. However, given the worse performance and
possibly higher fuel consumption, I agree that using a low-octane gas is
hardly a bargain.

Cheers,

Pete

"Pete" wrote
>
> Being a '94 model year, I doubt he still has warranty.

Nevermind that comment. Too many beers tonight...

Pete

"Pete" > wrote in message
...
>
> "Pete" wrote
>>
>> Being a '94 model year, I doubt he still has warranty.
>
> Nevermind that comment. Too many beers tonight...


Then I'll say it. Being a '94 model year, I doubt he still has a warranty.

I run the mid-grade in my 3 Series car and have done it for more than
120,000 miles and approaching 6 years. He won't exercise his warranty
because of the gas he uses.

On 6/24/2006 7:42 PM, Jeff Strickland went clickity-clack on the
keyboard and produced this interesting bit of text:
>
> "Pete" > wrote in message
> ...
>>
>> "Pete" wrote
>>>
>>> Being a '94 model year, I doubt he still has warranty.
>>
>> Nevermind that comment. Too many beers tonight...
>
>
> Then I'll say it. Being a '94 model year, I doubt he still has a warranty.
>
> I run the mid-grade in my 3 Series car and have done it for more than
> 120,000 miles and approaching 6 years. He won't exercise his warranty
> because of the gas he uses.

This brings up a question I've recently begun to ponder. From what I've
read all the octane level means is that it changes the pressure under
which the fuel will detonate. Higher octane is harder to detonate. The
purpose of this is so that the fuel won't detonate early in high
compression engines.

The question: What constitutes a high compression engine, low
compression engine and mid-compression engine? I suspect the engines in
the M cars are going to have higher compression engines, but what about
the other ones? My M60 has a compression ratio of 10:1. Is this high?

--
You got to be careful if you don't know where you're going, because you
might not get there. - Yogi Berra

"Jeff Strickland"wrote
> Then I'll say it. Being a '94 model year, I doubt he still has a
> warranty.

Yeah, I think Toby realized that and that's why he wrote
"out-of-warranty".

Pete

"Voinin" > wrote in message
...
> On 6/24/2006 7:42 PM, Jeff Strickland went clickity-clack on the keyboard
> and produced this interesting bit of text:
>>
>> "Pete" > wrote in message
>> ...
>>>
>>> "Pete" wrote
>>>>
>>>> Being a '94 model year, I doubt he still has warranty.
>>>
>>> Nevermind that comment. Too many beers tonight...
>>
>>
>> Then I'll say it. Being a '94 model year, I doubt he still has a
>> warranty.
>>
>> I run the mid-grade in my 3 Series car and have done it for more than
>> 120,000 miles and approaching 6 years. He won't exercise his warranty
>> because of the gas he uses.
>
> This brings up a question I've recently begun to ponder. From what I've
> read all the octane level means is that it changes the pressure under
> which the fuel will detonate. Higher octane is harder to detonate. The
> purpose of this is so that the fuel won't detonate early in high
> compression engines.
>
> The question: What constitutes a high compression engine, low compression
> engine and mid-compression engine? I suspect the engines in the M cars
> are going to have higher compression engines, but what about the other
> ones? My M60 has a compression ratio of 10:1. Is this high?
>

Sorta.

Your hunch is correct, higher octane will not spontaniously combust the way
that low octane fuel will, this is how high octane gas prevents ping. When
the car has a knock sensor (knock and ping are two words that are used
interchangeably, however I've been told that they are not really
interchangeable words -- but that is another post). Anyhow, if the knock
sensor detects knock (as when low octane fuel is introduced) the computer
can retard the timing so that the engine fires closer to TDC. This gives
slightly less power because the spark comes when the piston is already on
the way down, instead of just peaking over the top. A result of retarding
the timing a few degrees is that the motor runs a bit cooler to avoid
pre-ignition that comes from heat, but the cost of retarding the timing is a
loss of power. Frankly, the average driver will not miss the lost power on
his daily commute to and from the salt mine.

10:1 is on the edge of high compression. I have said several times that I
use the mid-grade fuel with never a hitch.