In the i3 manual, BMW makes the curious statement that they "recommend" using 91 octane gas, but the "minimum" octane rating is actually 89. What does that even mean? No one sells 91 octane gas where I live. There's 87 Regular, 89 Plus, and 93 Super. I don't use the REx very much, so the price difference isn't THAT much of a factor, but it seems silly to put 93 octane gas into my car when 89 meets the minimum requirement.
I assume that the REx runs at some higher-than-normal compression ratio that requires higher-than-87 octane gas. I'm guessing that BMW determined that 89 octane is the minimum required to prevent pre-ignition. But why in the world would BMW recommend any more than that? Why would it make any difference?
I assume that the REx runs at some higher-than-normal compression ratio that requires higher-than-87 octane gas. I'm guessing that BMW determined that 89 octane is the minimum required to prevent pre-ignition. But why in the world would BMW recommend any more than that? Why would it make any difference?