Thermal grease helps electronics dissipate heat and avoid damage, so it needs to be replaced if compromised or dried out to keep electronics running smoothly. If you don't have access to thermal paste, a wide range of specialized and common liquids or gels can be used in its place. Professional-grade alternatives include high-temperature automotive grease and dielectric silicone. Both are typically used for vehicle engines and provide heat dissipation for low-temperature settings.
Toothpaste has proven to be a very effective alternative for thermal grease, but only for a short duration. Toothpaste dries out quickly so it will serve as a grease replacement for only few boots. Mixing a petroleum jelly with toothpaste can improve its longevity. Since fluoride can be corrosive over a long period of time, you may want to opt for diaper rash cream if you're in a jam. Diaper rash cream is also a temporary solution but it won't corrode your electronics.
Avoid Coarse Items
Thermal grease replacements that are coarse or contain small, hard ingredients can do significant damage to your electronics. Coarse materials, such as those that exfoliate skin, can scratch the contacts on a heat sink, CPU or video card, damaging those parts. Significant scratches can lead to temperature increase and can cause your thermal grease or replacement to dry out more quickly.