3-Series (E46, E90)Chat relating to the BMW 3-Series from 1999 to Current. Models include: BMW 316i, BMW 318i, BMW 318Ci, BMW 320i, BMW 323i, BMW 325i, BMW 330i, BMW 328 Ci, BMW 328i, BMW 325i/xi, BMW 330Ci, BMW 320d, BMW 330d, BMW 335d.
I have a 2001 year 325i BMW . Does someone in this Forum tell whether it makes any difference in using either 87 Octane or 91 Octane Gas for my car(i always go for 91 octane).Gas prices in california are ghead .I usually drive in the city traffic conditions and sometimes though very rarely hit 90-95 Miles/hr on highway.
Ok... speaking from only what I know.. and I might be wrong... so someone correct me if I'm wrong here..
The different levels of octane in gasoline tell you how much fuel can be compressed before it spontaneously ignites. So... this is the down low so you can tell them the exact answer... Gas is comprised of crude oil.. then it goes to the refinery.. and then you get .. what they call hydrocarbon chains of different lengths... then its blended to form different types of fuels acourding to the length of the chain... such as butane... methan... and propane... and of course gasoline... well I know I'm getting on a tangent.. but octane is just one of those lengths of crude oil.. it can be compressed to a very high ratio before it combusts... so if your running 93 octane... thats 93% octane and 7% heptane... and will combust at a given compression ratio... so thats why you need to use a certain gas in a certain engine... all is relative with compression and octane. A higher octane fuel though... will be able to compress to a higher ratio.. therfor making your engine run at a slightly higher compression so it can combust after it mixes with H2O.
Thats some information I wrote about a year ago on this forum... should explain some stuff about octane that might pertain to your car...
First is it 91 RON or 91 AKI you are talking about (we need to separate the apples from the oranges). In the US the octane rating at the pump is AKI (a blend of RON or the Research Octane Number and the Motor Method Octane Number that gives us the AKI or Anti Knock Index). In the real world, a 91 RON equals a 87 AKI and unless your car is certified for or has been modified for more timing or a faster timing advance, higher octane will only help the seller of the fuel.
Very true about use what the book recommends, but be sure you understand the book, RON versus AKI. Another thing about premiuum fuel is it vaporizes or burns slower than regular grade fuel and can cause initial start up stalling in cold weather. My daily driver is a 1998 Neon with, among other mods a reflashed computer requiring a minimum of 91 Octane fuel and in very cold weather the first start of the day is a start and die, restart. In fact, Chrysler has a TSB on this subject (140897).
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