@brians1209 they’re a bit high, but not as high as what many here contend. Probably twice as thirsty as their RL counterparts.

@ChiChiWerx Is the J15 and the J50 engines fuel consumption realistic?

Well, fuel in jets is typically measured in pounds or kilograms, but to match your question, I’ll use liters. In the 1960s, fighter type aircraft carried anywhere from 2,300-2,400 liters (MiG-21 and BAC Lighting to 7,500 liters (F-4). The greatest internal fuel capacity carried by a fighter, at that time or any other, was most likely the Tupolev Tu-28P “Fiddler”, which held the title as the “world’s largest fighter”, but was really an interceptor aircraft, which probably carried 16,700 liters of fuel internally. Internal fuel capacity varied widely, but it was invariably based on the size of the aircraft. The bigger the internal volume, the more gas the jet will probably carry, as fighters typically will fill every possible open space not taken up with cockpit, electronics, hydraulic systems, flight controls or intake ducts with fuel. Additionally, almost every single jet fighter out there will carry external tanks to increase fuel carried, though they are the first thing jettisoned going into an air to air engagement. Given all the variables, it might be difficult to estimate a time aloft, but I’m going to attempt to give one to you. Bear in mind that mission profile also impacts time aloft greatly. A low level, high speed interdiction profile will burn far more gas than a CAP loiter. And afterburner usage burned a lot of gas, which is one reason why air to air engagements don’t usually last more than 2 minutes. Given all this, unrefueled mission durations (and most NATO profiles, even in training, included air to air refueling) were anywhere from 45 mins (MiG-21 and Lightning) to 2 hrs (Phantom). Now, you’re probably asking this because SP fuel burn is too high. I contend, though, most SP users simply fly around at 100% power on power multiplied engines, which IRL would burn fuel just as fast. This results in running out of gas within 5 mins. I can stretch out a flight on a realistically loaded jet to 20 mins or more, long enough to want to just land and be done, with the added benefit of a replica build handling and flying more realistically as the jet is heavy at the start and much less so at the end. I hate, hate, hate unlimited fuel!

F-4E has about 12000 Liter capacity with drop tank.
It has a 680 km combat radius.
So that's about 40 minutes cruise x 2 journeys plus about 30 minutes of combat.
about less than two hours in total.

Anyway it's definitely far more fuel efficient than SP.

Planes such as the Dassault Mystère family lasted like about 30-40mins in the sky. They carried like.. idk.. 6000L ?

It depends completely on the aircraft.
Almost all jets have different engines and different fuel capacity.