Porsche 911 GT3 Owner's Manual page 186

Capacities
Use only fluids and fuels authorized by Porsche. Your authorized Porsche dealer will gladly advise you.
Your Porsche has been designed so that it is not necessary to mix any additives with oils or fuels.
Engine
Coolant
Manual transmission
and differential
Fuel tank
Fuel quality
Power steering
Brake fluid
Windshield washer
Oil change quantity without oil filter approx. 9.3 quarts/S.75 liters
Oil change quantity with oil filter approx. 9.6 quarts/9.0 liters
Reference indication is the level on the oil dipstick.
Please observe the chapter "ENGINEOil" on Page 114.
approx. 7.39 U.S. gallons/28 liters
3.5 quarts/3.3 liters transmission oil SAE 75W-90, Mobilube PTX
approx. 16.6 U.S. gallons/63 liters
Your engine is designed to provide optimum performance and fuel economy using
unleaded premium fuel with an octane rating of 98 RON (93 CLC or AKI).
Porsche therefore recommends the use of these fuels in your vehicle.
Porsche also recognizes that these fuels may not always be available. Be assured that your vehicle
will operate properly on unleaded premium fuels with octane numbers of at least 95 RON (90 CLC or AKI),
since the engine's "Electronic Oktane
approx. 1.35 quarts/1.27 liter hydraulic fluid Pentosin CHF 11 S®
0.67 quarts/0.63 liters; use only Original Porsche brake fluid.
approx. 3.19 quarts/3 liters without headlight washer
approx. 6.06 quarts/5.7 liters with headlight washer
knock control" will adapt the ignition timing, if necessary.
™
Technical Data