Changing Gas - BMW Forum

benji84 · 03-06-2005, 05:52 PM

I just bought a 94 325is and i not sure if the car has been running on 87 oct or 91. I just filled up the tank with premium and i was wondering if the engine is gonna responed differently if all its life it has had regular gas. Will it just take some time to get used to it? Will it effect or hurt my engine in anyway. I havent noticed any thing wrong yet but have only driveing about 10miles on this tank. car has about 128miles

94BMW325i · 03-06-2005, 05:54 PM

Car might shake a little, and acceleration will not feel as smooth.

bitcore · 03-06-2005, 06:08 PM

You should put the lowest octane in the tank that prevents knocking or the lowest that the manual says.
mine says no less than 89 (mid-grade) so I put 89 in there every time.

The only thing that octane rating is, is the fuel's resistance to combust under pressure (knocking, or dieseling) You don't get more power from it. (as the marketing methods of gas stations will lead you to believe [Premium vs. Regular] to trick you into buying the more expensive gas)

benji84 · 03-06-2005, 06:13 PM

Quote:

Originally posted by bitcore@Mar 6 2005, 04:08 PM
You should put the lowest octane in the tank that prevents knocking or the lowest that the manual says.
mine says no less than 89 (mid-grade) so I put 89 in there every time.

The only thing that octane rating is, is the fuel's resistance to combust under pressure (knocking, or dieseling) You don't get more power from it. (as the marketing methods of gas stations will lead you to believe [Premium vs. Regular] to trick you into buying the more expensive gas)

[snapback]305059[/snapback]

So the higher the octane the lower the resistance? or is it the other way around?

And if i do experince runing rough should i switch to a lower octane or will it just take some time to get used to it?

e30fanm3 · 03-06-2005, 06:28 PM

it wont run any different, itll run the same unless you run like 104 which wouldnt be good. the only time it really helps is if the car has sat for a while

benji84 · 03-06-2005, 06:30 PM

ok thanks guys. I was thinking it wouldent matter to much but was just makeing sure.

Delmarco · 03-06-2005, 06:36 PM

my car had 94 as to the usual 93 and it ran like an M3....and when I once put 91 in there...my car was a 318i again....

there is a diff. but its subtle....my car is an auto so I can't speak for manual but I think mannys are more sensitive to octane conversion..

Cruzin 323is · 03-06-2005, 07:41 PM

higher the octane.. = better the gas... and better the gas... is better the car will repsond!

thekid · 03-06-2005, 08:40 PM

Quote:

Originally posted by Cruzin 323is@Mar 6 2005, 07:41 PM
higher the octane.. = better the gas... and better the gas... is better the car will repsond!

[snapback]305192[/snapback]

not exactly. The higher the octane the more resistance there is. If you put in too low octance then the gas combusts prematurely... causing knocking... this is bad. So why would putting in gas that combusts later then normal be good? or have any positive effect?

Ice90 · 03-06-2005, 11:19 PM

Go to howstuffworks.com and look up combustion engine ther is a section about octane of gasoline in there,

from what i know the higher the octane the less likely it is that the gas will combust b4 the spark due to compression, this means

if ur gonna be booting your car,, Put higher octane in if ur just a casual car just use mid or regular,,,

I use premium cuz i have a heavy foot,,

i consider it cheap insurnces u don't wann crack a block do to a misfire of a cylinder when ur car under load especially launching your car very hard on the engine and compression is high....

jshearer · 03-06-2005, 11:25 PM

Don't go lower than the manual tells you, it should be 89 octane. I have been running 89 since i bought the car without any problems, but since i just purchased my chip I have to use 91 or higher, so from now on its higher octane figure i will let the car run two tanks of 91 before i install the chip to make sure there is no 89 left in the tank.

bigred318 · 03-06-2005, 11:26 PM

i use 92, but i also have a chip

david

RedlinedRU · 03-06-2005, 11:53 PM

The higher the octane, the faster the gas will ignite. Octane does matter. Thats why turbo/SC cars have to have premium as well as high output engines. Many drag cars use at least 110+ octane gas (aka jet fuel) to promote faster exposions. Alcohol burns faster than gas so really hooked up racers run alcohol blowers etc. High compression and high revving engines do better with higher octane.

Delmarco · 03-07-2005, 12:15 AM

no chip....in fact the only performance mod on my car is 93 octane or 94/95 octane when i can get some....

trust me I feel the difference....aceleration and momentum is more consistent and smoother.....

when I had 91/92 I had to keep my foot on the gas in order to maintain momentun and keep up my aceleration especially on hilly roads....

as for 87/89 octane my car will never have to worry about getting that weak shit...cause I don't do lower than 93 oct.....

believe that!

benji84 · 03-07-2005, 01:06 AM

Quote:

Originally posted by Delmarco@Mar 6 2005, 10:15 PM
no chip....in fact the only performance mod on my car is 93 octane or 94/95 octane when i can get some....

trust me I feel the difference....aceleration and momentum is more consistent and smoother.....

when I had 91/92 I had to keep my foot on the gas in order to maintain momentun and keep up my aceleration especially on hilly roads....

as for 87/89 octane my car will never have to worry about getting that weak shit...cause I don't do lower than 93 oct.....

believe that!

[snapback]305533[/snapback]

Didnt even know you could by 93 or 94/95 from a gas station.