If the car has ANY warranty left... I wouldn't. Use what the dealership recommends. Different weight of oil can sometimes have adverse affects especially on newer cars. It can throw off sensors that read off of oil pressure. Ive seen it in a 350z where I put in the wrong weight and the VCT stopped working and the car went into limp mode. If its has no warranty left go ahead. Likely nothing will happen changing weight that little but just remember it could have adverse effects in the long run. Good Luck I know what your talking about with high temps I live in El Paso, but your climate is still hotter.