Porsche 928 ST1991 Owner's Manual page 74

Fuel filler cap
The fuel filler cap is located under the flap in
the rear quarter panel behind the right rear
wheel.
When putting the cap back on the fuel filler
neck, be sure cap is securely seated. Twist
cap clockwise, until it stops with an audible
click and then lock with the ignition key.
We recommend you turn off the engine
when filling the fuel tank.
Fuel tank capacity
Fuel tank capacity is listed under "Filling
Capacities"
Porsche does not recommend the use of
fuel additives.
If you lose your fuel filler cap, replace it im-
mediately with a cap of the same design to
reduce the possibility of a fire in a collision.
Fuel recommendations
Your Porsche is equipped with a catalytic
converter and must use UNLEADED FUEL
ONLY.
Minimum octane rating is 95 RON/85
MON "Premium unleaded fuel" (90 CLC or
AKI). Federal law prohibits use of leaded
fuel in this vehicle.
Regular unleaded fuel with a minimum oc-
tane rating of 91 RON/ 82 MON (87 CLC or
AKI) can be used temporarily, due to a built-
in "Electronic Octane™Knock Control", if
premium unleaded fuel is not available. In
this case avoid full throttle operation.
The use of UNLEADED FUEL ONLY is criti-
cally important to the life of the catalytic con-
verter. Deposits from leaded gasolines will
ruin the converter and make it ineffective as
an emission control device.
Cars with a catalytic converter have a smal-
ler fuel tank opening, and gas station pumps
have smaller nozzles. This will prevent acci-
dental pumping of leaded fuel into cars with
a catalytic converter.
Unleaded fuels may not be available outside
the continental U.S. and Canada. Therefore,
we recommend you do not take your car to
areas or countries where unleaded fuel may
not be available.
Octane ratings
Octane rating indicates a gasoline's ability to
resist detonation. Therefore, buying the cor-
rect octane gas is important to prevent en-
gine damage.
The RON octane rating is based on the re-
search method. The CLC (U.S. Cost of Living
Council octane rating) or AKI (antiknock
index) octane rating usually displayed on
U.S. gasoline pumps is calculated as re-
search octane number plus motor octane
number, divided by 2, that is written as:
RON+MON
or
2
The CLC or AKI octane rating is usually lower
than the RON rating:
95 RON equals
Always use unleaded fuel with octane rat-
ings of at least 95 RON or 90 CLC or AKI.
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.
R + M
2
90 CLC or AKI
73