Thermal paste is a small, inexpensive component that punches well above its weight in keeping a CPU cool, yet it's one of the most overlooked parts of a PC until temperatures start climbing and nobody can work out why. This guide explains the different types of thermal compound available, what actually matters when choosing one, and how leading products compare so you can pick the right paste for your rebuild or maintenance job.
Why Thermal Paste Matters
Even a perfectly flat CPU heatspreader and cooler base have microscopic imperfections that trap tiny pockets of air when pressed together, and air is a poor conductor of heat. Thermal paste fills these gaps, creating a much more efficient path for heat to transfer from the CPU to the cooler. Over time, especially with cheaper compounds, paste can dry out, crack or separate, meaning even a system that was never touched can develop rising temperatures purely from age, which is why reapplication every two to four years (or whenever a cooler is removed) is standard maintenance practice.
Types of Thermal Compound
Silicone-Based (Budget/Stock)
The paste often pre-applied to budget or stock coolers out of the box. Adequate for basic use but generally offers noticeably lower thermal performance than dedicated aftermarket compounds, and tends to dry out faster.
Carbon/Ceramic-Based
A step up from silicone-based paste, offering improved thermal conductivity while remaining non-conductive electrically, meaning an accidental small spill onto the motherboard poses no risk of a short circuit. A sensible, safe default for most home users.
Metal-Based (Non-Liquid Metal)
Compounds infused with metal particles (often silver) for improved conductivity over carbon/ceramic pastes, sitting in a middle performance tier. Still generally non-conductive as applied, though care should still be taken to avoid excess spillage.
Liquid Metal
Made from gallium-based alloys, liquid metal offers the highest thermal conductivity of any consumer compound, delivering a genuinely noticeable temperature improvement over standard paste in demanding builds. However, it is electrically conductive, meaning any spillage onto surrounding components risks a short circuit, and it can corrode aluminium (though it's safe on the copper and nickel-plated surfaces typically found on CPU heatspreaders and cooler bases). It's also not compatible with bare aluminium heatsinks and requires more careful, experienced application. Best suited to confident users specifically chasing maximum thermal performance rather than a general-purpose choice.
What to Look For
Thermal Conductivity
Manufacturers list a thermal conductivity figure (measured in W/mK), and while higher is generally better, the real-world difference between good mid-range and premium pastes is often smaller than marketing suggests for typical desktop use. Don't assume the highest number on the shelf is a dramatic practical upgrade over a well-reviewed mid-range option.
Longevity
Cheaper pastes tend to dry out and lose effectiveness faster, sometimes within a year or two, while quality pastes can maintain good performance for several years before reapplication is needed. If you don't want to think about reapplication frequently, longevity matters more than a marginal thermal conductivity advantage.
Ease of Application
Some pastes are noticeably thicker and harder to spread evenly, while others have a looser, more workable consistency. For a first-time or infrequent user, an easier-to-apply paste reduces the risk of an uneven application, which matters more for actual cooling performance than the raw conductivity spec.
Electrical Conductivity
Non-conductive pastes (the vast majority of standard compounds) are far more forgiving of minor application mistakes, making them the sensible default unless you specifically want liquid metal's performance and are confident in your application technique.
Pro tip: Less is more. A pea-sized dot in the centre of the CPU (for most modern CPUs) spreads evenly under the pressure of the cooler mounting without needing to be manually spread beforehand. Manually spreading paste with a card or spatula before mounting often introduces air bubbles that a properly seated cooler's own pressure would have avoided.
Well-Known Thermal Paste Brands Compared
- Arctic (MX-4, MX-6) — extremely well-regarded for offering strong thermal performance at a genuinely affordable price, with good longevity and an easy-to-spread, non-conductive, non-curing formula that many consider close to a benchmark default choice for most rebuilds.
- Noctua (NT-H1, NT-H2) — a highly trusted cooling brand whose thermal paste matches the reliability reputation of their fans and coolers, offering strong, consistent performance and often bundled with their own cooler products, though sold at a modest premium versus budget options.
- Thermal Grizzly (Kryonaut, Conductonaut) — Kryonaut is a well-regarded premium standard paste offering excellent performance for enthusiasts, while Conductonaut is their liquid metal option for users chasing maximum performance and comfortable with the extra care liquid metal requires.
- Cooler Master (MasterGel) — a solid, accessible mid-range option, often bundled with Cooler Master's own coolers, offering reasonable performance for general use without a premium price tag.
Application Checklist
- Fully remove old paste from both the CPU and cooler base using isopropyl alcohol (90%+) and a lint-free cloth before applying fresh compound.
- Apply a small, appropriately sized amount (guidance varies slightly by CPU size — check current recommendations for your specific socket).
- Mount the cooler with even, firm pressure, following the correct tightening pattern (typically diagonal, in stages) if using a screw-mounted cooler.
- Avoid excessive paste, which can squeeze out to the CPU edges without improving performance, and in rare over-application cases can even slightly reduce it.
How to Choose
- General maintenance or first-time reapplication: a reliable mid-range non-conductive paste like Arctic MX-4 offers excellent value and low risk.
- High-performance or enthusiast builds: a premium option like Thermal Grizzly Kryonaut offers a genuine step up for demanding workloads.
- Maximum thermal performance, confident application: liquid metal such as Thermal Grizzly Conductonaut, used carefully and only on compatible surfaces.
- Budget rebuilds where reliability matters more than peak performance: Cooler Master MasterGel or a similarly priced reputable mid-range compound.
How Often to Reapply
There's no single fixed schedule that suits every system, but as general guidance, a mid-range paste on a system with average use should be checked and likely reapplied every two to three years, while a premium compound may comfortably last three to five. Signs it's time to check regardless of schedule include rising idle or load temperatures compared to when the system was newer, or any time a cooler has been removed for another repair, since reseating a cooler on old, disturbed paste rarely gives as good a result as a fresh application.
Final Thoughts
Thermal paste is inexpensive relative to the rest of a PC build, so there's little reason to compromise on a reputable, well-reviewed compound. For the vast majority of home repairs and rebuilds, a quality non-conductive paste applied carefully in a small, centred dot will deliver excellent, reliable cooling performance for years.
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