We would travel to DP's folks home, a 2 & 1/2hrs drive about every 6wks up til now - our daughter is now 2yrs old

All the time she had formula, I would fill 2 x bottles with boiling hot water out of the kettle & pop into an Avent twin bottle holder moments before we would leave for the journey

Also I would put her formula milk powder in a Avent sealed divided container.

The water would be nice & warm (of course not hot) by about an 1hr to 1.5hrs depending on whether the temperature outdoors was a hot or cold day

When it was a hot day I would pop in a little bottle of cold water, whether to add to the water if too hot OR to cool her down with a bit of water (though that was when she was about 6mths).

Hope that's helped some