I've spoken to so many people and its like asking people who they will vote for President... 50/50 Putting regular will destroy the pistons because of premature combustion, blah, blah, blah

Others say, the gas is the same andthere is just an unnoticeable performance difference and the cars computer makes up for the change in grade.

Anyone REALLY know the truth?

 

Your car will run fine. The computer will adjust. You will lose HP. How much who knows (I'd estimate 5 to 15 HP tops). But with the lower octane you could notice some knocking in the engine over time. Knocking isn't ever good so long term I would assume some damage could be done.

Where I live premium fuel is only about 10 cents to 15 cents higher then reg. So if you pump in 15 gallons your only looking at about $2.00 or so difference in each tank. Say you fill up once a week, in a whole year you'd only save about $100 or so. I'm sure most of us will spend a $100 on something worthless in the next few weeks so to me it isn't even worth putting in regular gas.

 

Agree. BTW, in NY, its .30 - .35 more expensive for Premium. So, approx $300-$400/yr extra.

What do you think about tire and wheel insurance for run flats- $600??

 

Unfortunately the knocking you speak if is actually detonation, and detonation can burn a piston. If you burn a piston, you kill the motor, and I doubt BMW will cover it. Burnt pistons don't happen on accident, and you could do serious damage instantaneously depending on how severe the detonation is. Even if you don't kill it right off, you could get an area of the piston hot enough to weaken it, which could be a ticking time bomb that could surface at any time.
Speaking of knocking... The computer alters a few things to keep the "knock count" within it's acceptable limits as it is. I would think at the very least, it would sense a much larger knock count, and start dropping ign timing, fuel mapping, turbo boost etc.. to try to control it. Obviously this would lessen your motor's hp output. Having written this second paragraph, I must tell you I'm a bike guy, not a car guy. I'm speculating on what the computer might do. The mechanical repercussions would be the same on any gasoline engine, but with the complex software a car computer possesses compared to a bike's computer, I can only guess about that.
I like bikes

 

You have a 550i, I would stick with premium.

 

Do you drink Tap water or spend money on bottled water?

Tap, buy regular, bottled buy premium.

Over the course of a year you will far out spend money on bottled.

btw, I drink tap water.

 

Wheel insurance I'd say depends on your area. I see your in the New York area so you deal with winter (I'm in Wisconsin) and the great pot holes it brings in the spring. If your running run flats on your Bimmer and get a nail in the tire or whatever you have to replace the tire, at about $200 to $300 a piece. Also running lower profile tires you run a much higher risk of getting a bent wheel. The wheel insurance can pay for its self that is for sure. But as with any insurance/add on at the dealer you got to feel comfortable in buying it. Personally if you got the $600 I'd buy it, chances are you'll use at least once during its life.

 

Read your BMW's manual...you'll get the most honest answer. I was using 91 octane and decided to to try 93 octane, it's only 2 cents more per gallon. The car felt lighter and my mileage went up. I was getting 25.0 - 25.2 and now I'm at consistent 25.8 mpg on the same route. I've noticed what brand of fuel used makes a difference also. Bmws seem very susceptible to fuel changes.

 

I am not taking a shot at anyone or the original poster...this is just an opinion.

Why are we even having this discussion? You own a BMW. It's a luxury car. Treat it like one! I know the price of gas is high, but how much are we talking about here? $5 savings a tank? Please don't give me the over the course of the year it would be argument. That is nonsense as well. You bought a nice car so you should maintain the nice car. Are you going to put regular fossil oil instead of synthetic when you change your oil to save a few bucks?

I used to hear this argument over on the Infiniti forums when I was a regular there. You buy a $50K M45 and now your worried about saving by putting cheaper gas in it and that is when gas was $2.80 a gallon for 93!!! It makes me crazy that someone would even consider this. I personally want the best for my car so it performs at it's best. If I can't afford it or I can, but I "think" it's too expensive then trade the car. Get a Honda Accord that is recommended that it uses 87 octane. Not knocking Honda. I have a Honda in the family and yes it is great that we only have to use 87. It actually runs better with 87 than 93, but it's a Honda and that's what they design their engines to use.

Anyway, I wanted to vent because I think this debate is a tired one that is unnecessary. :thumbsdown:

 

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