That is not really too much of a problem. Out of curiousity, a friend of mine put thermometers inside the back windows of his two cars- a black Charger with black interior and a B5 blue Road Runner with a white interior. By late afternoon the black car was at 116 degrees and the blue one was 112. Not a difference you would ever notice.
Now this is a remarkable thing. Certainly only among Chrysler enthusiast would there be inquiring minds that would use the scientific method on this problem.
Just can't figure a "Chevy" doing this.
At any rate I would imagine this is not in his decision process. He is probably more concerned with aesthetics.
Also I know from experience that a white interior is less “practical” than a black interior. If you are going to get in a car with work cloths, on black is the way to go.
I do wonder if there are not some variables, which are being overlooked in your experiment.
Number one: Were the thermometers in direct sunlight?
If so, it would seem to me that would mask the true ambient interior temperature and give artificially high readings in both cars. (The higher the reading the less the difference makes)
Number two: Were the thermometers calibrated? If not, one might read one or two degrees high and the other one or two degrees low. This might increase the differential by as much as four degrees. That then would be an 8-degee spread.
Number three: I assume the blue car was a dark blue. Perhaps B5? If the “control” car was yellow or white this might give another 4-degree difference between the dark blue (which is between black and white) and the lighter color. That again would give an 8-degree spread even at the high end. It might be more significant to the ambient. Just guessing.
Number four: This is not scientific, but I know even if I am not in direct sunlight I feel hotter in a dark cotton shirt then a light cotton shirt. That may have something to do with reflected or inferred light being absorbed.
Number five: Another variable is tinted glass. I couldn’t wait to put a tinted windshield in. You can really tell the difference driving. (Actually I did wait till I found a 20 dollar one in the junk yard after mine got a rock crack.)
And lastly,
Number six: When I come out on a hot day, I am certain that I can tell the difference between my yellow car with a white interior and my brown car with a black interior. And I leave my widows down.
All that being said, if the color is a toss up, I’ll take 80 over 85. I’ll take 90 over 95.
