Think about your question.

You do not want to add heating or cooling. Meaning the garage will always be close to the ambient temperature.

Adding insulation in the attic will slow the temperature changes(night to day/etc) , but will not keep the interior that much warmer/cooler without heating/cooling.

Yes it will do that. Our garage is insulated all around (walls and ceiling) and it typically stays probably 40-50 degrees even when it's very cold outside (well below freezing).

Of course when the garage door goes up, you loose a lot of heat, but we still notice a huge difference in temp vs. outside, which was nice for our cats/dogs.

As a benefit, I'm sure it saves energy from the home too, since of course that's where the heat in the garage is really coming from.

I don't know if the payback is there, it's probably not from a financial standpoint, but from a comfort standpoint it's well worth doing, in my experience.

I'm sure it saves energy from the home too, since of course that's where the heat in the garage is really coming from.

No sense letting the heat coming from the poorly sealed living space go to waste in an uninsulated garage. I know my lawn tools and kid's yard toys appreciate the extra warmth over the cold winter months.

The house I grew up in had a north facing garage that was insulated and fully plastered on the interior. (it also had curtains and an epoxy floor, it could have been used as living space) It was heated a bit by one register and also an open vent which allowed some heat to come in from the furnace room which was in the basement to one side of the garage. (The garage level was two steps down from the main house so the basement ceiling was a bit above the floor level of the garage) When the room above the garage and the rest of the basement were finished, they were given a separate hot water heat system and a salvaged cast iron radiator was placed in the garage. Of course this raised the overall heating bill for the house, probably mostly because of the additional heated living space, but since they were two separate systems, you could see that heating the garage and attic over the garage made the heating bill for the main part of the house go down-- I guess heating these other spaces at a lower temp dampened the effect of there being a large unheated area (originally) at the north of the house.

Of course a lot of people would question the cost benefit of fully finishing a garage (and it was also on a steel deck with a full basement underneath it, as well, another expense) but I vastly prefer a finished easily cleaned, heated transition space between the outside and the main house to a cold, unfinished space, having lived with both. It's also great getting into room temperature cars both summer and winter vs. a blistering hot or freezing cold car.
(Although there is some argument that a car may rust faster in a heated garage with winter salt).