As ZaltysZ noted, it looks like the answer is no.

Since the very beginning I have adjusted my Rads but having read this thread decided to leave them fully open on a MP session for the entire session. I didn't notice any difference or penalty - not one that would be considered a disadvantage.

I am now unsure as to wether the Rads have any drag impact but having said that I will continue to control my rad settings as a matter of good habit just in case something changes regards this in a future patch.

What a joke it would be if it's true, super advanced CloD physics/FM doesn't simulate drag caused by protruding plane parts. I can't tell any difference either when flying the G.50 with fully open or almost closed rads and you notice even 10 kph extra or minus in an aircraft which is as slow as the G.50.

I don't even understand this discussion, it's clear it's aerodynamics basics, more streamlined objects move easier through air then less streamlined objects (as in objects with other objects sticking out of them). What do you think wind tunnels are for? Even paint is known to cause drag on airplanes.

Ding!

At which point a reasonable man would take pause and ask himself..

Do I think 1C made a basic flight modeling error?

Or

Is it more likely that the 'users' who provided no proof made an error in testing?

Anything is possible I guess!

But if I had to place a bet on 'who' made an error

My money would be on the starbucks barista who only dabbles in flight simulation when not playing Quake over someone like Oleg who makes a living at it.

Where as your mileage may, and clearly does vary

ace of aces, if we go by that rule, then CLoD should be the perfect game, with no errors, but it is not, there has been a minor bug list as big as your ego since release, so its perfectly plausable that oleg (or luthier) did something wrong with the aerodynamic moddeling of the radiator.

This topic is a joke. 14 pages of people saying "omg if it's true that's bad" but nobody's actually taken the time to establish if it's true or not.

I checked.

The OP is correct.

Difference between fully open and closed radiator on the BF 109 E-4 in CloD is 0%/0 km/h.

Doesn't matter what throttle/prop setting, doesn't matter what height. And yes, i flew straight and level.

Just saying "I checked" is not proof. Sorry. Do you have a track file?

It was not my intention or job to proof anything.

I don't think the devs would need proof either, because it's obvious enough and they should know that already.

If you need proof, better check it yourself then.

Are you sure about that? Were you fully open at the beginning and fully closed at the end? If so, did you trim your plane after closing those rads? I can´t be really sure, but opening my rads fully always resulted in my planes tendency to climb and vice versa.