Porsche 928 GTS 1994 Owner's Manual page 78

Octane ratings
Octane rating indicates a gasoline's ability to re­
sist detonation. Therefore, buying the correct
octane gas is important to prevent engine dam­
age.
The RON octane rating is based on the research
method. The CLC (U.S. Cost of Living Council
octane rating) or AKI (anti knock index) octane
rating usually displayed on U.S. gasoline pumps
is calculated as research octane number plus
motor octane number, divided by 2, that is writ­
ten as:
RON + MON or R + Μ
2
The CLC or AKI octane rating is usually lower
than the RON rating:
For example:
95 RON equals
WARNING
Never carry additional fuel in portable con­
tainers in your car. Such containers, full or
partially empty, may leak, cause an explo­
sion, or result in fire in case of a collision.
Always use unleaded fuel with octane ratings
of at least 95 RON or 90 CLC or AKI.
Gasolines containing alcohol and ether
Some areas of the U.S. require oxygenated
fuels during certain portions of the year. Oxy­
genated fuels are fuels which contain alcohols
(such as methanol or ethanol) or ether (such as
MTBE).
Under normal conditions, the amount of these
compounds in the fuel will not affect driveability.
You may use oxygenated fuels in your Porsche,
provided the octane requirements for your ve­
hicle are met. We recommend, however, to
change to a different fuel or station if any of the
following problems occur with your vehicle:
2
• Deterioration of driveability and performance.
• Substantially reduced fuel economy.
• Vapor lock and non-start problems, especially
at high altitude or at high temperature.
• Engine malfunction or stalling.
90 CLC or AKI
79