i live in south florida, Fort Lauderdale, and the summer here is not only long, with unbearable heat and humidity from about May until late September.
i was reading that using a higher viscosity oil is recommended in climates like this.
Honda still changes my oil since it is still under warranty. correct me if i am wrong, but the Fit takes 10w-30 oil.
that should be fine for this heat, but just wanted to make sure. and when my warranty is up, not sure if i should continue to use Honda's recommended factory oil, or use a synthetic oil.

 

i use 5w-20 fully synthetic mobil 1...live in tampa and i've never had any problems.

 

I also thought the fit used 10w-30 but looked in the manual. The honda recomendation is 5w-20. Just use this and u will be fine