[dmdad]

Hi guys, I'm new to the forums so please forgive me if this is not in the right place. I did look through the archives and don't see my question answered. Here goes:

So I don't want to rehash old arguments about octane choice -- I've been buying the highest grade available, which is 91 in my area. Friday I'm taking a road trip to a nearby state with 93 octane available. When I fill up, do I go with the 93? This is not a price issue. My concern is that my engine (2012 535) is now used to 91 and there might be some engine controller or something that wouldn't like to recalibrate, especially when I'll be back to 91 within a tank or two. My dad has a 2013 528 and the dealer told him to use any grade he wants, but to be consistent. In other words, use 87 or 89 if you want, but just don't switch back and forth. I would have never any thought about it and just used whatever the highest octane is each time I filled up. However, after hearing this from my dad I started to wonder if there was more going on than I realized.

Does anyone know enough about this to have an informed opinion?

Thanks in advance.

[AP]

It makes no odds, the electronics will adjust every cycle for the fuel being fed in at that time whatever octane value it may.

[ManiacGT]

Yeah, I think you're looking for something to worry about here. Just put in the best fuel you can, the car will sort itself out, its designed to get the best from the fuel it 'senses' via knock sensors and the like.

[HighlandPete]

As said, nothing to worry about.

Also remember the engine management is adapting in real time, continuously modifying to load, temperature, etc., so will not be 'recalibrating' to a tank of fuel. It is doing so, multiple times a second on the fly.

Just don't use fuel below the 'minimum' octane rating for the engine.

HighlandPete

[The X Men]

Originally Posted by dmdad

Hi guys, I'm new to the forums so please forgive me if this is not in the right place. I did look through the archives and don't see my question answered. Here goes:

So I don't want to rehash old arguments about octane choice -- I've been buying the highest grade available, which is 91 in my area. Friday I'm taking a road trip to a nearby state with 93 octane available. When I fill up, do I go with the 93? This is not a price issue. My concern is that my engine (2012 535) is now used to 91 and there might be some engine controller or something that wouldn't like to recalibrate, especially when I'll be back to 91 within a tank or two. My dad has a 2013 528 and the dealer told him to use any grade he wants, but to be consistent. In other words, use 87 or 89 if you want, but just don't switch back and forth. I would have never any thought about it and just used whatever the highest octane is each time I filled up. However, after hearing this from my dad I started to wonder if there was more going on than I realized.

Does anyone know enough about this to have an informed opinion?

Thanks in advance.

I would tell your dad not to listen to his salesman anymore. As usual, some of those salesmans know less about the car they are selling than some of us here in this forum. 87 octane is not ok to use in your dad's 2013 528i, the minimum octance is 89 and recommanded is 91. Putting 87 octane in a turbo charged engine that is not design for it can cause damage in the long run. As far as switching octane from fillup to fillup, the computer in your car will adjust to the octane in your tank within minutes, there is no need to stay with the same octane from tank to tank.

[dmdad]

Thanks everyone for the helpful responses. I've only got about 3000 miles on my car... very much looking forward to a nice road trip.

[BigKutta]

I think BMW has made this confusing and dealers are trying to use this "minimum 89 Octane" thing to lure buyers who might be worried about using premium gas.

I had been driving a BMW for 11 years before I bought my F10 and always used 91 or above. So when I was doing my final pre-sales inspection of my F10, I happened to open the fuel door and right there the sticker said something about minimum 89 Octane. I was surprised and asked the sales rep and he said the BMW no longer require premium fuel (although 87 is the basic, so 89 is not exactly the base fuel). I was perplexed. When I got home with my car and looked in the manual, it said the BMW recommends 91. Now why would they confuse the buyer? Stick to a minimum of 91 and be consistent.

You will be surprised at how many Merc and BMW drivers pull up next to me at a gas station and put 87 Octane in their cars. I suppose, even if you drive a $50-60k car, you try and save $1 at the pump, so maybe this is BMWs way of warning people that 89 is the bare minimum.

Back to your point, it doens't matter about the consistency of the fuel grade. Just get what you can find and mix. I usually use 2-3 gas stations around my work depending upon what I am closest to, and sometime I use 91, and sometime 93 Octane fuel. I (and most of the world) have done this all my life and there is never an issue.