Yes. Gasoline can differ.
From Your M5 Manual:
"Use high-quality brands
Field experience has indicated significant differences
in fuel quality: volatility, composition,
additives, etc., among gasolines offered for sale
in the United States and Canada. Fuels containing
up to and including 10% ethanol or other
oxygenates with up to 2.8% oxygen by weight,
that is, 15% MTBE or 3% methanol plus an
equivalent amount of co-solvent, will not void
the applicable warranties with respect to
defects in materials or workmanship.
The use of poor-quality fuels may result in
drivability, starting and stalling problems
especially under certain environmental conditions
such as high ambient temperature and
high altitude.
Should you encounter drivability problems
which you suspect could be related to the fuel
you are using, we recommend that you respond
by switching to a recognized high-quality brand
such as gasoline that is advertised as Top Tier
Detergent Gasoline.
Failure to comply with these recommendations
may also result in unscheduled maintenance."
- page 175 BMW USA M5 manual (2006)
Here is a link on best gasoline companies in terms of detergents and additives which is mentioned in your BMW manual:
Top Tier Gasoline
<table><tbody><tr><td colspan="2" style="text-align: center;">TOP TIER Gasoline Retailers:</td> </tr> <tr> <td colspan="2" style="text-align: center;">
</td> </tr> <tr> <td style="width: 241px;">
76</td> <td style="width: 276px;">
Petro-Canada</td> </tr> <tr> <td style="width: 241px;">
Aloha Petroleum</td> <td style="width: 276px;">
Phillips 66</td> </tr> <tr> <td style="width: 241px;">
Chevron</td> <td style="width: 276px;">
QuikTrip</td> </tr> <tr> <td style="width: 241px;">
Chevron Canada</td> <td style="width: 276px;">
Rebel Oil</td> </tr> <tr> <td style="width: 241px;">
Conoco</td> <td style="width: 276px;">
Road Ranger</td> </tr> <tr> <td style="width: 241px;">
CountryMark</td> <td style="width: 276px;">
Severson Oil</td> </tr> <tr> <td style="width: 241px;">
Entec Stations</td> <td style="width: 276px;">
Shell</td> </tr> <tr> <td style="width: 241px;">
Esso</td> <td style="width: 276px;">
Shell Canada</td> </tr> <tr> <td style="width: 241px;">
Exxon</td> <td style="width: 276px;">
Sunoco Canada</td> </tr> <tr> <td style="width: 241px;">
Kwik Trip / Kwik Star</td> <td style="width: 276px;">
Texaco</td> </tr> <tr> <td style="width: 241px;">
MFA Oil Co.</td> <td style="width: 276px;">
The Somerset Refinery, Inc.</td> </tr> <tr> <td style="width: 241px;">
Mileage Stations</td> <td style="width: 276px;">
Tri-Par Oil Co.</td> </tr> <tr> <td style="width: 241px;">
Mobil</td> <td style="width: 276px;">
Turkey Hill Minit Markets</td> </tr> <tr> <td style="width: 241px;">
</td> <td style="width: 276px;">
U.S. Oil</td></tr></tbody></table>