What Heat Does to the Gear You Leave in the Truck

Your rig is a storage locker that spends its summer in an oven. Here is what that costs you, and what to move.

Most of us think about heat in terms of the engine. Coolant, transmission temps, the gauge we watch on a long climb. The stuff riding in the cab and the bed gets no attention at all until something fails, leaks, or tastes wrong.

The numbers are worse than most people assume. A study led by climatologist Nancy Selover at Arizona State University and Jennifer Vanos at UC San Diego, published in the journal Temperature in 2018, parked cars in Tempe on days when the ambient temperature was in the 100s and measured what happened inside. After one hour in the sun, cabin air averaged 116 degrees and dashboards averaged 157 degrees. Cars parked in the shade still reached about 100 degrees inside, with dashboards averaging 118.

That is one hour. A rig sitting at a trailhead for a weekend, or parked in Moab while you are out on foot, is running that experiment for days.

Here is what actually degrades, roughly in order of how much it will annoy you.

Lithium batteries lose capacity permanently

Heat is the main enemy of lithium ion cells, and the damage is cumulative rather than temporary. A power station, a headlamp, a spare drone battery or a phone left on a dashboard does not simply perform worse while hot. It comes back with less capacity than it had, forever.

Two habits fix most of this. Never store a lithium battery at full charge in a hot vehicle, since high state of charge plus high temperature accelerates the loss faster than either alone. And get the cells out of the cab and into the coolest, most insulated space you have, which on most builds is a drawer low in the bed rather than anywhere near glass.

Aerosols and pressurized cans

Look at the back of a can of tire sealant, brake cleaner, bear spray or sunscreen and you will find a storage warning, usually somewhere around 120 degrees Fahrenheit. A dashboard at 157 is well past that. A door pocket in direct sun is not much better.

This is the category where the failure mode is not just wasted product. Move anything pressurized into shade, low down, and ideally in a container that will hold a mess if a can does let go.

Tire pressure, and the mistake people make correcting it

The usual rule of thumb is that tire pressure moves about 1 psi for every 10 degrees Fahrenheit of change. That means a set aired down to 18 psi on a cool desert morning can read noticeably higher by mid afternoon without anyone touching a valve.

The trap is bleeding pressure at the hottest point of the day to hit a number, then finding yourself genuinely underinflated at dawn. Set your pressures cold, note what they read hot on the same day, and use that difference as your reference rather than chasing a single figure.

Adhesives, plastics and anything mounted

Phone mounts, dash cams, trim clips, tablet holders and the double sided tape holding all of it are the first casualties of a 157 degree dashboard. Adhesive mounts that have survived two winters will let go in a single August afternoon.

If it matters, mechanically fasten it. If it cannot be fastened, expect to re seat it every season and carry spare tape.

Fluids and consumables

This is the least glamorous category and the one that most often ruins a trip.

Water in a translucent jerry can plus sun equals algae, faster than most people expect. Store water in opaque containers or in shade.

Sunscreen and bug repellent degrade with heat and time, and a bottle that has spent a summer in a door pocket is not the same product it was when you bought it. Same for anything in a blister pack in the glovebox.

Anything flavored, brewed, cured or extracted is a slow chemical process that heat speeds up. That is worth understanding rather than just avoiding, because it is the same principle whether you are storing coffee, olive oil, whisky or a bottle of eLiquid.

Nicotine eLiquid is a useful example because the good stuff is unusually vulnerable. Most of the category is synthetic flavoring, which is relatively stable. But naturally extracted products are not built that way. Black Note, for instance, makes its tobacco liquids by cold macerating real cured leaf in a food grade solvent over six to eight weeks, so what is in the bottle is an extraction rather than a flavor compound. Heat, light and oxygen keep that reaction running after it leaves the factory, which shows up as a darker liquid and a duller, flatter taste. The manufacturer’s own guidance is the same as it would be for any extraction: cool, dark, sealed, and out of the sun. A center console in Arizona is the worst place in the vehicle for it. A closed drawer or a soft cooler is the best. It is an adult product and it stores like one.

The general rule holds across the whole category. If it was made slowly, it will keep changing, and heat decides how fast.

Where to put what

If you are reorganizing after reading this, the hierarchy on most builds looks like this, coolest to worst:

• A drawer or box low in the bed, insulated, out of direct sun. Batteries, consumables,
• A soft cooler, even without ice. Anything you actually care about tasting
• Under a rear seat. Acceptable for tools and
• Door pockets and seat backs. Aerosols only if you have no better option, and never in direct
• The dashboard and any surface under glass. Nothing you plan to use

None of this requires new gear. It is mostly a matter of deciding, once, that the dashboard is not storage.