Well I got a response from Chevron regarding their diesel fuel formulation (see below). Just for reference here's what the X5 35d manual says "The Engine of your BMW is designed for diesel with a low sulfur content: Ultra-low sulfur diesel ASTM D975-07a. Only refuel with ultra-lowsulfur diesel. The percentage of biodiesel in the fuel must not exceed 5%, referred to as B5."
Here's what I got from Chevron:
Your inquiry has been forwarded to us here at Chevron Fuels Technical
Service.
As part of the S15 (ULSD) regulation, the EPA requires that new labels
be placed on every diesel dispenser in the United States, excluding
California. The label should be located near the indicator that shows
how many gallons you have pumped into your diesel vehicle.
All Chevron and Texaco diesel dispensers, excluding those dispensers in
California, were appropriately labeled by June 1, 2006.
Note - The above labeling requirements only apply to the United States,
Puerto Rico, and the US Virgin Islands. Canada does not have dispenser
labeling requirements.
Cetane Number:
* In general, the processing required to reduce sulfur to 15ppm also
reduces the aromatics content resulting in an increase to the cetane
number.
In the United States, the properties of diesel fuels are under the
auspices of an industry organization, the American Society for Testing
and Materials (ASTM). The ASTM Designation for diesel is D 975 -Standard
Specification for Diesel Fuel Oils. D 975 sets limits (requirements) for
the values of these properties. Most of the requirements of D 975 are
the minimum ones needed to guarantee acceptable performance for the
majority of users. In addition, the specification recognizes some
requirements established by the United States Environmental Protection
Agency (USEPA) to reduce emissions. Chevron abides by all of these
specifications.
The Cetane number limit (minimum) is 40.
There is a Federal cetane spec. for Ultra Low Sulfur Grade No. 1-D and
2-D (Grade No 2-D would be the one used in most all on-road vehicles). D
975 requires an aromaticity of 30 % vol. max. or a cetane index of 40
min.. Our understanding is that this is a Federal requirement and did
not originate with ASTM. Typical Chevron production excluding California
and Hawaii is 48 cetane. Chevron guarantees product limits only;
typicals are average properties, and higher and lower values are to be
expected.
Typical California Chevron production is 52 because of additional
requirements of the California Air Resources Board (CARB) for vehicular
diesel fuel.
Typical Hawaii Chevron refinery production is 61.
There is no maximum ASTM Cetane number limit.
U.S. average cetane is 45. There is no way to tell what the "at the
retail pump" cetane value would be and is not required to be posted by
law, as is the case for gasoline octane minimum rating.
ULSD will not change these typical averages much. Not lower. Maybe a
little higher. (1-2).
For additional information about diesel fuels see the following link for
our Diesel Fuels Technical Review
http://www.chevron.com/products/prodserv/fuels/documents/Diesel_Fuel_Tec
h_Review.pdf
Chevron Diesel with Techron D
A Ultra Low Sulfur Diesel (ULSD) with an advanced cleaning additive
specially formulated to help keep critical diesel engine parts clean,
lubricated and free from performance-robbing deposits.
Techron Diesel could be introduced into more US
markets in 2010.
At this time no defined time line.
Use station Finder with Filter Option Diesel location checked:
http://www.chevron.com/products/ourStations/stationfinder/
Would have to phone station or physically check the pump if it is
containing Techron D.
Some companies marketed "premium diesel" before an industry definition
for what "premium" meant was established. Because of this, there had
been some confusion on what, if anything, made "premium" diesel
different from other diesel.
On July 16, 2003, the National Conference on Weights and Measures (NCWM)
created a new definition for Premium Diesel.
To qualify as a Premium Diesel the following four properties of the fuel
had to be met (ASTM is the American Society for Testing and Materials):
a) The cetane number must be 47 or greater (using ASTM D 613 test
method)
b) The thermal stability must be sufficient to meet a minimum
reflectance limit of 80% (as determined by test ASTM D 6468)
c) The fuel must show suitable low-temperature operability by passing
either the Cloud Point Test (ASTM D 2500) or Low Temperature Flow Test
(ASTM D 4539) at the tenth percentile minimum ambient air temperature
for the region and time of year where the fuel will be sold. Ambient
temperatures for areas are noted in ASTM D 975
d) The lubricity must be sufficient to produce a scar no larger than
520 microns in diameter as determined by ASTM D 6079 (HFRR)
If the diesel meets theses requirement it will be posted on the pump
that it is a Premium Diesel.
Most of the time all Chevron & Texaco Diesel meet the Premium
requirement therefore you might not see the premium designation.