I hate to break it to you but ethanol has less energy by volume and actually reduces MPG. Scientifically proven. It does raise octane ratings buy not mpg.

 

sorry to tell you, but that is a 100% completely false statement.

 

Octane reduces pre detonation or knock. Does not mean more mpg. Do some research on ethanol and you will find that it lacks the energy compared to gas. Ask an e85 person what their mpg is when they fill up. Sorry but I have spent too Much time I chemistry class back in the day to agree with you. Ethanol is the worst alternative to Dino fuel even if it puts money in or farmers pocket( which my family does). I am
Stating facts and not fiction. If you ever dind a non-ethanol fuel pump and fill up with 100% gas, you will understand

 

well you guys can "do your research" all you want, but here is some real-world data for you to chew:

i filled up with 87 at valero on my highway drive back home. i went 150 miles and got 33mpg (idrive and actual--filled up again when i got home to confirm idrive). my previous best highway was 28mpg on 93, in fact on the way down there i was getting only 27.

gotta say, not only is 87 cheaper, but for me, this is a pretty obvious improvement. i get significantly better gas mileage. 5mpg+ more is astonishing.

gonna be sticking with 87 i believe.

 

IF you insist on doing that I recommend you use only Tier 1 regular gasoline. That said, I would not use regular grade gasoline, on a regular basis, in any BMW that recommends Premium gasoline. IF you are doing it to save money, drive fewer miles or drive slower etc. instead.

It does tickle me why anyone (I'm not saying that's the case for you) would spend $40K - $80K+++ for a car and then try to save at MOST $200-$300/a YEAR by buying regular vs premium gasoline.

 

1. if i'm getting 5mpg more with lower octane, i think it's safe to say i'm saving a hell of lot more than $200 per year
2. if i'm getting 5mpg more with lower octane, sounds to me like my engine runs better on lower octane anyway
3. supposing #2 isn't true, i will most likely trade my car in within a year for something i like that won't have the mechanical issues this thing seems to have while ON 93 octane. if there are going to be long-term effects of the 87 octane gas in my car, that's fine by me, i don't plan on owning it when that happens. judging by my car's rocky past, i doubt it's going to have any trouble at all with having a bazillion problems completely impertinent to octane levels anyway.
4. i didn't pay anywhere close to 40k for my car, i paid in the 20s. even so, it tickles me how some BMW owners (you) get your panties in a wad by other BMW owners (me) that don't care to follow BMW's "recommendations."

quite frankly, i could have responded and said that my daughter was in a freak accident and my health insurance isn't covering it so i'm trying to save every penny i can, and i would have just made you look like a complete dick for your post. alas, that isn't the truth and i'm not going to lie, but i said it from the start i don't care to hear what bmw recommends, nor do people need to keep insisting that they don't understand how a bmw owner would be cheap. i'm cheap because i don't like my bmw and don't plan to own it much longer. period. if that isn't good enough reason, go back to #1 and #2 and then stop your bitching. it's not any of your business why i choose to run my car with KY jelly if i so choose to do so. and i'm really, really sorry if it makes other bmw owners feel cheap or unworthy. my bad.

/rant (for now)

 

truly, to put you "how could a bmw owner be cheap???" responders to ultimate rest, please read this article:

http://bimmer.roadfly.com/bmw/forums/e81/9083308-1.html

"Thomas Plucinsky, BMW Product and Technology Communications Manager told us all BMW engines are designed to run on 91 octane. All performance testing, including EPA emissions and fuel mileage, is done with 91 octane. However, though BMW is all about performance, their motors will run on 89 or 87 octane without damage. The knock sensors pull the ignition timing back and eliminate detonation."

 

On this topic, I have a few points...

(1) As to if BMW allows 87 octane. My wife's 2009 X5 with the N52 6 cylinder engine even says that 87 is allowed. Here is a snippet of the manual:



Don't know about e60 or older engines. My 2006 e60 N52 does not say that 87 octane is allowed.

(2) As to mileage. It would seem to me that the engineering logic goes as such. The engine gets power from the violent detonation of fuel. In this case, the car is designed for maximum power using 91 octane. Just to be clear, octane does not relate to energy content of the fuel, only the ability to resist detonation due to pressure and heat. So, if the energy content of the fuel is the same, and the car can handle the increased octane, then letting the compression build higher will result in a bigger reaction when the spark detonates the fuel. If you retard the timing to reduce the knock, then you reduce the reaction to the detonation of the fuel and thereby also reduce the force that propels the car. That should equal less mileage. Any test needs to use the same exact base fuel under in the same conditions over the same course using the same car.

(3) In higher altitudes, you often see lower octane grades at the pump - like 85. I've even seen owner's manuals from other manufacturers that allow 85 octane instead of 87 octane in Western Kansas, Colorado, Wyoming and some other higher elevation areas. So, in higher elevations, you may also need less octane. Now, I don't know if today's cars already sense the altitude and compensate one way or the other.

 

You made your points - I'm very sorry for the personal problems you're facing and hope they resolve quickly. I'm glad you didn't rename me RICHARD - it wouldn't have earned you any bonus points.

That said, I probably should have bolded my disclaimer [ "(I'm not saying that's the case for you)" ] so you didn't take the example I provided so personally.

OH - If you try the KY jelly gasoline substitute let us know what kind of mileage you get