I would guess that the lightness we feel at high speeds is do to the new 5 series being one of the first truely sporty cars (with a heavy V8) to managed a near 50/50 weight split. Normally anything that goes that fast is fron heavy just due to the size of the engine.

I too flet the lightness, but it did not feal unsafe. I only went up to 130 due to considerations of my passanger. But at that speed I was still accelerating and my 545i seemed very eager to quicken the pace.

 

Same here.
It didn't felt unsafe, just a little lighter at the front.

 

jtxc, approximately 450 more posts and you'll be a Specialist too!

(At the rate Iceman is going, he'll be one in a few hours!! )

 

jtxc, approximately 450 more posts and you'll be a Specialist too!

(At the rate Iceman is going, he'll be one in a few hours!! ) [/quote]


I'm spending too much time here...

 

91 octane in north america is recommended for 530 and 545 by BMW ...higher octane does NOTHING..(When you are talking about 98 in sweeden..it s the same as 91 in NA)if you want to spend your money to get 100 and feel macho...go ahead...As for M5 you should go with the minimum octane rating recommended by BMW (which I have no idea what it is but probably different because it s a totally different beast...the rest is Marketing. period

Octane is not a secret formula for boosting performance..contrary to popular belief...

 

91 in NA is the same as 98 over here in Germany. That makes sense, since BMW recommends (in Germany) using 98 octane (what is, as we just learned, 91 in NA).

Now, using the 100 octane in Germany is not harming the engine. It can be better for the engine, or it's just simply the same. But the other point is, that the big chains over here (Shell, Aral, Esso,...) are switching the 98 octane out. Shell does not sell any 98 octane anymore, Aral is currently switching, and the gas stations who allready switched don't have 98 octane anymore. Esso and the others will follow this example soon.
So, again... The so called experts say, 100 octane is better. I don't know if this is marketing only, or if this is true - and I don't f*cking care! It can be better for the engine, or it's just as good as 98 octane. Whatever... In the very near future we will have 100 octane only. It doesn't hurt to use it allready.
And, nobody said that octane is a secret formula. We were a little cunfused, because in NA and in Europe we have "octane", but they are different. And that was something a couple ppl (like me!!!) didn't knew.
So - thanks for the info!

This is the iceman, over and out!

 

As I understand it, higher octane fuel burn slower than lower octane. Pinging or detonation occurs when the cylinder temp get to high and the fuel/air mixture ignites (due to heat) before the spark plug fires. Thats why you would get run-on even after your turn off the car (ignition system off) because the continued rotation of the pistons draws in more fuel/air mixture and they fire due to heat. In modern hi-perf cars the ignition system retards the timing to lower the heat, while reducing power so you avoid pinging. If you put in higher octane fuel, which burns slower, you can advance the timing, which increases power. US cars are designed to run of 91 octane but the car will retard the timing if you use lower octane fuel. But there is a limit to how much octane will improve performance.