At three o’clock on a January afternoon, a car that has stood in a shopping centre car park since breakfast is hotter inside than most of us would guess. South Australia’s RAA put numbers on it in 2019, when it left two cars in the sun for a piece on what you can cook in a parked car. Twenty minutes was enough for both cabins to pass 70°C. The darker car went on to 83°C, and an egg left on the dash was cooked within half an hour.
Now think about what else is sitting in that heat for eight hours a day, five days a week. There is a battery under the bonnet. There is paint on the roof with nothing between it and the sun, and there is black rubber around each door and window. On Australian cars those three wear out early, and you can do a fair bit about all of them for very little money (some of it for nothing).
A Battery Hurt By Summer Usually Fails In Winter
Call-outs for flat batteries jump with the first cold snap of the year, and most drivers blame the cold for it. Heat is the real culprit, according to the NRMA’s page on cold weather and car batteries. High temperatures speed up the chemical activity inside the battery and shorten its life, whereas cold merely slows the reactions down, and “a cold snap will sort out the good from the bad,” as the club puts it. A battery that struggles in June has generally been weakened in the summer before.
How long should one last here? Terry Smith, who spent a dozen years as an NRMA patrolman in Canberra, told Region that the city’s hot summers and freezing winters often limit a battery to around three years. RACQ’s figure for a quality battery is three to four.
If yours is past three years old, have it tested before summer and again before winter.
RACV recommends a battery test as part of a check-up when summer begins, and it warns that the corrosion heat causes inside a battery is permanent. NRMA members can ask for a battery health check without paying for it. Between tests, keep an eye out for these:
- slow cranking on a cool morning.
- headlights that dim while the engine idles.
- white or green crust on the terminals.
- a case that bulges at the sides (a bulging battery is finished, test or no test).
Replacing a doubtful battery at home costs the price of the battery. Leaving it until it dies on a country road adds a tow and a lost day of the holiday.
Sun Damage Shows On The Roof, Bonnet And Boot Lid Long Before The Doors
Walk around an older car that has spent its life outdoors and compare the roof with a door. The door will probably still have its gloss, while the roof looks flat or even chalky. Those top panels face the sky all day and take far more sun than an upright panel does.
The part being damaged is the clear coat, a transparent top layer that gives modern paint its shine and contains the UV protection for the colour below. Under years of sun and heat it oxidises. Dullness is the early stage, and a polish can still rescue the panel at that point. Once the clear coat has started to lift and flake, though, polishing is useless and the panel has to be resprayed. Owners of red, black and other dark cars should check more often, as dark paint absorbs more heat.
What Wax And Ceramic Coatings Can And Cannot Do
Plenty of people believe a coating works like sunscreen for the car. Bridie Schmidt corrected that in a guide she wrote for the NRMA in November 2025 on how to protect your car from the sun. At one or two microns thick, a coating is too thin to block UV. Its use is in keeping oxygen and dirt away from the clear coat, where the UV inhibitors are found.
A ceramic coating generally costs from about $1,000 and needs reapplying after two to five years. If your car is garaged at night, Schmidt’s view is that ordinary wax and careful washing may well be enough. The cheapest protection in her guide is free, and it is simply to park out of the sun whenever you can.
Why Bird Droppings Need To Come Off Straight Away
Bird droppings are acidic, and on a hot panel they can mark the clear coat permanently within hours.
A bottle of water and a microfibre cloth in the boot are all the equipment required. Wet the dropping well, give it a minute, and lift it away gently, because rubbing it dry will scratch the paint. Salt deserves equal care. When you come home from the beach, hose down the bonnet and roof before the spray has a chance to dry on.
Window And Door Rubbers Crack Slowly, And The Signs Are Easy To Miss
When did you last look at the rubber strip along the bottom of your driver’s window? Hardly anyone does, and it is the most exposed piece of rubber on the car. It lies in direct sun for hours and is scraped by the glass whenever the window is lowered.
Rubber stays flexible because of protective compounds that are blended into it during manufacture. Sunlight, heat, oxygen and ozone gradually use those compounds up, after which the rubber shrinks, hardens and begins to crack. The corners of the window frames usually crack before the straight runs do, since the rubber is under the most strain there.
You will not see a warning light for any of this. What you may notice is extra wind noise at 100 km/h, or a wet door sill after heavy rain, or wipers that smear the windscreen even though the blades look intact. Wiper blades are the least durable rubber on the vehicle, and in Queensland, the Territory and the north of WA a fresh pair each year is money well spent.
The upkeep is simple enough to do while the car is being washed. Wipe each seal with mild soapy water so that grit does not grind into it when the door closes, dry it, and then apply a water-based rubber protectant that includes a UV blocker. Petroleum-based dressings should be kept off seals. Companies that make rubber-care products caution that these can strip out the protective compounds and speed up the cracking. If a seal has already split, no product will mend it, and a new seal is the only cure.
Parking In Shade Saves The Paint And Rubber, But The Cabin Still Gets Dangerously Hot
Shade is good for the car and nearly useless as a way of keeping the inside cool, and it is important to keep those two facts apart. RACQ has tested parked cars with light paint and dark paint, with tinted glass, with a sunshade fitted and with the windows left slightly open, and in each case the cabin temperature differed by only a few degrees. A child or a dog must never be left in a parked car, however shady the spot looks.
For the bodywork the picture is much better. According to the NRMA guide mentioned earlier, the shady side of the street, an undercover car park or a row of trees can bring surface temperatures down considerably. A windscreen sunshade that fits tightly, together with shades on the side windows, will also keep UV off the steering wheel, the seats and the centre console. Battery, paint and rubber all benefit when the bonnet and roof are out of direct sun.
Side shades are useful during a drive as well, particularly for children in the back who sit right beside the glass for hours on a long trip. Custom-fitted ones, Sunziro car window shades for instance, are cut to the shape of a particular model and attach to the door frame with hook-and-loop strips, so the window can still be wound down with the shade in place.
If the only shade near your house is a tree, expect more droppings and sap, and inspect the paint weekly. A car that is left standing for weeks at a time is better off under a cover, and the NRMA advises choosing a light-coloured, breathable one and washing and drying the car before it goes on.
When To Do Each Job Through The Year
Drivers in different parts of the country will want to time these jobs differently. In the tropical north the heat barely eases, and a battery test once a year is sensible there. Further south, in inland towns with frosty winters, the test that matters most is the autumn one. People near the coast should worry less about polish and more about rinsing off salt.
With that in mind, here is roughly how the year could run:
- In late spring, get the battery tested, wash the car properly and put on a coat of wax or sealant.
- Over summer, clean off droppings as soon as you see them and rinse the car after any trip to the beach. Wipe the door and window rubbers once a month.
- In autumn, test the battery again if it is more than three years old.
- Replace wiper blades whenever they begin to streak.
You may already keep a list of preventative home maintenance jobs for the house, in which case the car can be added to it. A long Christmas drive is a good reason to bring the checks forward, and a battery test fits easily onto a holiday checklist beside the sunscreen and the esky.
