Stu Pengelly placed the slab of pork in a baking tin on the car seat of his red Datsun Sunny in Perth, Western Australia, for around 10 hours.
“It worked a treat!” he said in a Facebook post with pictures of the cooked meat cut into slices to demonstrate its doneness.
Pengelly also gave the temperature as it increased throughout the day, culminating in a “staggering 81 degrees Celsius inside temperature” (177.8 degrees Fahrenheit) at 1 p.m.
Other social media users responded to the post with humorous comments, asking for an invite to the next roast, and relating their own experiences cooking in a heatwave.
But Pengelly’s post also contained some serious advice, warning people not to leave their children or dogs in a vehicle in the heat.