Does hot weather create less or more power?

Does it increase or decrease mpgs?

Does higher octane have any advantage in hot weather?

I have watched my mpgs go down in the past few weeks...I have my opinion, but would like to hear what others think on the subject?

 

Hot air is less dense. Less oxygen is available so less power will result. This is the theory behind cold air intakes. The difference between winter and summer ambient air temps is enough to make a noticeable difference.

However MPG wouldn't suffer as a result. It might use less fuel since there is less oxygen with warmer ambient temperatures. The Fit's ecu accounts for this and meters less fuel for a correct mix.

Using the A/C more will have an impact. Summer fuel blends may have an impact (these start shipping in May I think).

Edit: if the engine runs hotter it may be more prone to knock resulting in more frequent timing retard. Higher octane would help prevent this, however this has not been shown to increase power or MPG in an engine designed to run on lower octane fuel.

 

the above is absolutely correct, i just wanted to add that in the summer if you're not using A/C you may have your windows down and drive more enthusiastically. i know i do. in previous cars i've seen a one or two MPG drop in summer, all my windows are wide open and i'm driving a bit fast. i mostly drive local, though, on the highway you would see more of a difference with open windows. im the fit i'm not sure because i'm only on my second tank of gas.

 

windows open = mass amounts of drag (in the fit)

 

Good points in all the above statements

 

I haven't seen a difference in mileage from when I bought mine in the spring to now in the blazing heat with A/C.