4Driver4

All things equal, probably nothing.

westcoast4.2

It may be a $4 dollar difference but that's per fill up. So times that by say once a week, that's $20 a month. That's more than just a cup of coffee.

Press

or run it on regular gas and report your findings

TXurS6

ah, but there is. Running at higher compression ratios give you higher efficiencies. As audikillsbmw points out, the 4.2 has an 11:1 compression ratio versus a more typical 9:1 compression ratio on cars that run 87 octane.

"A high compression ratio is desirable because it allows an engine to extract more mechanical energy from a given mass of air-fuel mixture due to its higher thermal efficiency."<ul><li><a href="http://en.wikipedia.org/wiki/Compression_ratio">click</a></li></ul>

ESN

Ding! Ineluctable, as always, curmudgeony as it may be [I like curmudgeony]

2.7t @Altitude

Easy to Lose (cheap gas). Hard to gain $$$

BernieBenz

I basically agree. Depends how and where you drive. The hows have been well covered. If driving at 5000' altitude and above there is absolutely no need nor justification for using premium fuel, even with forced induction.

schnellmb

which Audi/VW does not recommend. they want a top tier gas.

absolutcq20v

I've used regular for a year plus with no noticable difference...but less of a wallet-ache.

audikillsbmw

Methanol?