my mini has racked up over 150,000 km on the odometer, and by now the AC puts some strain on the engine, so I try to avoid using it. Which means in these heatwaves, I drive everywhere with the windows "rolled" all the way down. (only in slower stop and go traffic, on the highway windows go up and the AC goes on speed 2).

Anyway, I've noticed with the windows down:
-I'm getting better mileage.
-I have less traction on hard turns.
-My front wheels will sometimes slip a little.
-the car will do a slight hop if I hit a bump.

I didn't pay enough attention in science class, but I think the aerodynamics of the mini suck air into the cabin and sort of lift it... Does this make sense or am I an idiot?

 

Idiot is such a strong word.

Just kidding, I couldn't help myself, sorry.

Better mileage is probably due to the AC being off. You would most likely get even better mileage if you put the windows up and kept the AC off, though it would not be too healthy for you.

The second and third observations are probably related to you being able to "hear" what is happening better with the windows down.

I have no idea about the hop in your MINI's drive with the windows down. Maybe it is excited to motor that way? But unless you are traveling quite fast I do not think the windows down will do anything except create drag, not lift.

Any other opinions or WAGs?

 

lol thanks for sugar coating it.

But I meant better gas mileage compared to the spring months when I had the windows up and had no ac running.

The hop is more of a sideways motion. Like when you drive in really windy conditions or on dirt roads really fast. I have good tires, but my car moves laterally ever so slightly.

Anyone else want to try driving for a week with the windows all the way down and see if you notice anything.

What are WAGs?

 

WAG - Wild A$$ Guess

 

maybe heat warms up your tire? or since you have such a high miles (as you mentioned) maybe shocks or spring for bumps????

 

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My guess....
car has some wear on tires+ suspension...so grip is not as good...
ac off...means slight increase in power with ac off....generly better mpg for non highway driving where aerodynamics are not as important as highway driving....
Then add you know what the car is capable of and may push it a bit harder than when it was newer....
More squeal....
Also some road surfaces get a bit slick in heat....oils in/on it can accumulate....that is why the first few minutes of a rain storm is the most dangerous.

 

The breaking point for windows up with A/C running and windows down no A/C is at 52MPH. Mythbuster's did the testing

 

Every car's aerodynamics is different. I can't recall what they used for that test but I know for a fact it wasn't a MINI.

 

Very true, but it DOES show, the faster you are moving, the more important aerodynamics are!!
On a heavy truck, those side-skirts on a trailer that end about where the rear tires can start are only cost effective when trucks go faster than about 60 mph...
Aerodynamics generally follow the inverse square rule for drag increases....that means everytime you go 2X As fadt you get 4X the increase in drag!!
That is why comparitivly small decrease im speed usually yields a larger % increase in savings!!

 

I was just pointing out that YMMV...