I'm not sure I followed you there.....So on it's own it's not good enough for mayo, but with frozen water bottles it is?
Right now I use dry ice and I'm just looking for something more convenient for those long trips.
I know they are designed as coolers, not freezers. The web site states that they keep items 40 degrees cooler than the surrounding air. So if it's 90 degrees out, then it's probably at least 70-75 in your car (with the A/C on), therefore the cooler is at 30-35, which is about the same as a home fridge.
Coleman 40qt Power Chill
• New motor design provides quiet, long lasting performance
• 120V power supply included
• Cools to 40°F below surrounding temperature
• Portable - plugs into your cigarette lighter
• Use in two positions, upright or chest
• Adjustable shelf divider
• Molded handles for easy lifting and carrying
• Patented, adjustable door opens on right or left side
• Perfect for the office, dorm rooms, RVs, campers, truck cabs, cars, SUVs