Written by Danielle Arnold
Quick answer: PLA can soften in a parked car. Victorian Government health advice says a parked car can be 20 to 30 degrees hotter inside than out, and sunlit dashboards run hotter again. Our PLA grades list a 53°C heat deflection temperature. Print dash mounts in ASA, ASA-CF or PC-ABS, and keep PETG Basic for shaded, light-duty interior parts.
A printed phone mount or console organiser can look perfect on the bench and come back bent out of shape after one hot afternoon in a parked car. Avoiding that is not complicated: work out roughly how hot the part will get, compare that with the heat figures on the filament's data sheet, and leave a margin.
This guide pulls together published measurements of parked-car temperatures, lines them up against the heat deflection temperatures (HDT) on our data sheets, and suggests materials for dash mounts, interior clips and outdoor parts. It finishes with design tips that help printed parts get through an Australian summer.
How hot does a parked car get?
There is no single number. Cabin temperature depends on the weather, the sun's angle, the car's colour, window tint and how long it has been parked. These are the most useful figures we found from government, motoring body and university sources.
| Source | Conditions | What they found |
|---|---|---|
| Better Health Channel, Victorian Government | General health advice | The temperature inside a parked car can be 20 to 30 degrees hotter than the temperature outside. |
| RACV | RACV testing, 30°C outside | Vehicle interiors can reach more than 70°C within minutes. |
| Dadour and colleagues, Forensic Science International, 2011 | Cars parked in the sun in Perth | Cabin temperatures can be more than 20°C above outside air, and a maximum of 70°C was recorded. A black car was typically about 5°C hotter inside than a white car on a hot summer day. |
| Vanos and colleagues, Arizona State University, published in the journal Temperature, 2018 | Six cars on summer days of about 38°C and above in Tempe, Arizona | After one hour in the sun: cabin air about 47°C, dashboards about 69°C, steering wheels about 53°C and seats about 51°C. In the shade, dashboards averaged about 48°C. |
You can read the Better Health Channel advice and the Perth parked-vehicle study record online. The same heat is why children and pets should never be left in a parked car.
We could not find a published Australian measurement of dashboard surface temperatures, so the Arizona study is the best available guide for dash-mounted parts. Treat it as an indication rather than an Australian benchmark. Putting the figures together, the Victorian advice suggests cabin air of roughly 55–65°C on a 35°C day, and the Arizona study found sunlit dashboards running about 20°C hotter than the cabin air around them.
Reading the heat figures on a data sheet
Our data sheets give a heat deflection temperature for most materials. HDT is measured to ISO 75 at 0.455 MPa: a standard test bar is loaded with a small, fixed force and heated until it bends by a set amount. Some sheets also list a continuous use temperature, a long-term rating rather than a short heat test.
Neither figure promises that a printed part will hold its shape. Test bars are solid, while printed parts have walls, infill and layer lines. A mount that holds a phone or clamps onto an air vent is also under load the whole time it is warm. Treat HDT as a ceiling and choose a material whose HDT sits comfortably above the hottest temperature the part will see. Our heat deflection temperature chart lists every material in the range.
| OzFDM material | HDT (ISO 75, 0.455 MPa) | Bed temperature (data sheet) | Hot car verdict |
|---|---|---|---|
| PLA Basic, PLA+, Matte PLA, Silk PLA, High Speed PLA | 53°C | 25–60°C | Keep it out of the car |
| PLA-CF | 60°C | 30–60°C | Keep it out of the car |
| PETG+ | 68°C | 50–70°C | Shaded, light-duty parts only |
| PETG Basic | 74°C | 70–80°C | Shaded, light-duty parts only |
| ABS+ | 85°C | 80–110°C | Interior parts, but ASA handles sunlight better |
| ASA and ASA-CF | 88°C | 100–120°C | Dash, rear shelf and exterior parts |
| TPU95A | 95°C | 20–60°C | Flexible interior parts |
| PC-ABS | 112°C | 90–110°C | The hottest spots, including dash mounts |
Against the temperatures above, every PLA grade sits below the Arizona dashboard average and below the cabin air you could expect on a 35°C day. PETG Basic clears those figures, but without much margin. ASA, ASA-CF and PC-ABS leave a wide margin, and our PC-ABS product page names automotive interiors as a suitable use.
What to print for each job
| Part | Where it sits | Our pick | Why |
|---|---|---|---|
| Phone, GPS or dash camera mount | On the dashboard, in direct sun | PC-ABS, ASA or ASA-CF | The hottest surface in the car, and the mount carries weight |
| Air vent clips and vent mounts | Near the windscreen, often in sun | ASA or PC-ABS | Clips hold tension all day, so give them extra margin |
| Console organisers, cup holder inserts, door pocket trays | Below the window line, mostly shaded | PETG Basic, or ASA for sunny spots | Cooler than the dash, but cabin air still gets hot |
| Parcel shelf and rear window parts | Behind glass in direct sun | ASA, ASA-CF or PC-ABS | Similar sun exposure to the dashboard |
| Exterior clips, covers and brackets | Outside, in sun and weather | ASA or ASA-CF | Our ASA product page highlights UV and weather resistance |
| Anti-rattle pads, cable tidies and grips | Inside the cabin | TPU95A | Flexible, with a 95°C HDT on our data sheet |
Check your printer before you order. ASA, ASA-CF and PC-ABS need high bed temperatures and are best printed in an enclosure: Bambu Lab's filament guide rates ABS, ASA and PC as not recommended on open-frame printers, and our PC-ABS product page asks you to confirm your printer offers an enclosed printing environment. Our ASA-CF product page lists a hardened steel nozzle and an enclosed printer as essential. If you print on an open-frame machine such as the Bambu Lab A1, our guide to the best filament for the A1 and P2S explains what it handles well.
Whatever you print, mount phones and cameras where they do not block your view or an airbag, and follow your state's road rules.
Design tips for parts that live in a car
- Add walls, not just infill. Extra perimeters make a part stiffer, so it is less likely to sag or twist as it warms. Solid, thick sections hold up better than thin shells.
- Keep arms short. A long cantilevered phone arm or a thin spring clip is the first place a warm part gives way. Shorten spans and add ribs or fillets where the load is.
- Choose lighter colours for parts in the sun. Dark surfaces absorb more sunlight and run hotter. The Perth study saw the same effect across a whole car, with black cars about 5°C hotter inside than white ones.
- Orient for the load. Layers are the weak direction, so print clips and arms so the bending load runs along the layers rather than peeling them apart.
- Use metal threads. Heat-set inserts give screws a brass thread to grip instead of relying on threads formed in the plastic.
- Consider annealing, carefully. Annealing is a controlled bake after printing that can raise the heat resistance of some materials. Parts can shrink or distort during the process, so try it on a spare print first. Our annealing guide covers the basics.
- Test before you trust it. Leave a spare print in the car through a hot week before you rely on a mount to hold an expensive phone. A windscreen sunshade also keeps direct sun off the dashboard.
Shop the materials in this guide
- ASA: UV-resistant filament for exterior parts and sun-exposed interiors.
- ASA Carbon Fibre: matte carbon fibre ASA with the same 88°C HDT as ASA.
- PC-ABS: a 112°C HDT for dash mounts and the hottest interior spots.
- PETG: PETG Basic for shaded, light-duty interior parts.
- 1.75 mm TPU95A Filament - 1 KG: flexible pads, grips and cable tidies.
Frequently asked questions
Will PLA+ survive in a hot car?
We would not rely on it. PLA+ has the same 53°C heat deflection temperature as our other PLA grades, and a parked car can pass that on a warm day. Our PLA Basic product page specifically advises keeping PLA parts away from hot cars.
Is PETG good enough for car parts?
For light-duty parts out of direct sun, PETG Basic is a reasonable choice with a 74°C HDT, higher than PETG+ at 68°C. For anything on the dashboard or behind glass, choose ASA or PC-ABS.
Does filament colour make a difference?
Colour does not change the HDT on the data sheet, but a dark part absorbs more sunlight and runs hotter than a light part in the same spot. For parts in direct sun, a lighter colour gives you a little extra margin.
Can I print ASA or PC-ABS on an open-frame printer?
We do not recommend it. Bambu Lab's filament guide rates ASA and PC as not recommended on open-frame printers, and our PC-ABS product page calls for an enclosed printing environment.
Does annealing make PLA safe for a car?
It can raise PLA's heat resistance, but parts may shrink or warp, and our data sheets do not list heat figures for annealed parts. For a car, ASA or PC-ABS is the more predictable choice.
