According to Fliegerführer Atlantik on 1 December 1943: a Ju 88 C-6's radius of action (with a fuel reserve for combat) was 900 km and endurance 6 hours; fuel load 3580 litres. With two external tanks radius of action was 1350 km and endurance 9 hours. Cruising speed at sea level was 350 km/h and maximum speed 430 km/h.
Source:
http://heritage.canadiana.ca/view/oo...415/31?r=0&s=5