Porsche carrera gt-2004 Manuel D’Utilisation

Maintenance, Car Care

127

Unleaded fuels may not be available outside the 

continental U.S. and Canada. Therefore, we rec-

ommend you do not take your car to areas or 

countries where unleaded fuel may not be avail-

able. 

Octane ratings 

Octane rating indicates a fuel’s ability to resist det-

onation. Therefore, buying the correct octane gas 

is important to prevent engine “damage”. 
The RON octane rating is based on the research 

method. The CLC (U.S. Cost of Living Council oc-

tane rating) or AKI (antiknock index) octane rating 

usually displayed on U.S. fuel pumps is calculated 

as research octane number plus motor octane 

number, divided by 2, that is written as:

The CLC or AKI octane rating is usually lower than 

the RON rating: 
For example: 95 RON equals 90 CLC or AKI 

Fuels containing alcohol and ether 

Some areas of the U.S. require oxygenated fuels 

during certain portions of the year. Oxygenated fu-

els are fuels which contain alcohols (such as meth-

anol 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 vehicle 

are met. We recommend, however, to change to a 

different fuel or station if any of the following prob-

lems occur with your vehicle:
– 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. 

Fuels containing MMT 

Some North American fuels contain an octane en-

hancing additive called methylcyclopentadienyl 

manganese tricarbonyl (MMT). 
If such fuels are used, your emission control sys-

tem performance may be negatively affected. 
The check engine warning light on your instrument 

panel may turn on. 

If this occurs, Porsche recommends you stop us-

ing fuels containing MMT.

Portable Fuel Containers 

sult in fire in case of an accident. 
f Never carry additional fuel in portable contain-

ers in your vehicle. 

RON+MON

2

R+M

2

or