[PFNog]

I use Leatherique - heard many good things about it a number of years ago and have been using it ever since. The have a cleaner and a conditioner so their cleaner may be exactly what you need.
Echo the heat thing with a slight clarification- I would avoid putting the seats in direct sunlight (sunlight is rough on everything- I have a cab, so my seats already get a lot of UV). Put the car with seats in it in the Sun with closed windows and let it get that summer heat soak before and after treating the seats. Then wipe off any excess that hasn’t been absorbed. I find it’s best to apply with a glove or bare hand - so you can get it even and don’t waste product conditioning a towel/sponge.