YETI Rambler 20 oz Stainless Steel Vacuum Insulated Tumbler – Infrared Review
Tested at 66°F | IR Photography Included

The YETI Rambler 20 oz Stainless Steel Vacuum Insulated Tumbler shown side-by-side in infrared (left) and visible light (right)
Introduction
The YETI Rambler 20 oz Tumbler is engineered to keep your beverages hot or cold for extended periods. Constructed with 18/8 stainless steel and featuring double-wall vacuum insulation, it is built to endure daily wear while providing exceptional temperature retention. The design includes a secure lid that minimizes spills, making it a reliable companion for both indoor and outdoor activities.
Test Setup
Thermal Imaging: We used infrared (IR) photos to measure surface temperature changes over time.
Elevation: 4,400 feet above sea level (At this elevation, the boiling point of water is 204°F rather than 212°F at sea level.)
Water Temperature: 204°F (Boiling)
Ambient Temperature: 66°F
Observation Duration: 40 minutes
Key Temperature Readings and IR Photos
Empty
66.9 °F – 66.6°F – 66.2 °F
Before any liquid is introduced, the tumbler’s top, middle, and base all register near ambient temperatures. The slight differences (with the top marginally higher) likely reflect minor environmental variations or sensor positioning.
Pouring (Initial Contact)
67.6 °F – 66.8°F – 66.4 °F
At the moment the hot water contacts the tumbler, the top edge warms slightly more than the middle and base. This indicates that the upper rim is the quickest to conduct heat, while the insulated walls delay the transfer to the rest of the surface.
30 Seconds
67.7 °F – 66.6 °F – 66.2 °F
After 30 seconds, the top shows a minimal increase, suggesting that while heat transfer has begun, the insulation is effectively limiting immediate conduction. The middle and base remain virtually unchanged, maintaining near-ambient temperatures.
1 Minute
70.4 °F – 66.6 °F – 66.2 °F
Within one minute, the top temperature jumps noticeably (by almost 3°F), indicating that the heat from the liquid is starting to spread along the upper wall. The lower sections remain insulated, as evidenced by the stable readings at the middle and base.
1 Minute 30 Seconds
71.9 °F – 66.6 °F – 66.0 °F
At 1:30, the top continues its upward trend as heat conduction from the liquid becomes more apparent. However, the middle and base show no significant change, underscoring the tumbler’s effective barrier against rapid heat transfer in those areas.
2 Minutes
74.5 °F – 66.8 °F – 66.2 °F
Two minutes in, the top now registers a more substantial rise. The widening temperature gradient—with the top now notably warmer—indicates continued heat migration, while the base remains almost completely insulated.
2 Minutes 30 Seconds
76.8 °F – 66.9 °F – 66.3 °F
A steady progression is evident; the top increases further as heat continues to build, yet the middle and base remain close to their original values. This demonstrates that the heat is concentrating at the upper portion of the tumbler.
3 Minutes
79.1 °F – 67.1 °F – 66.3 °F
At three minutes, the top clearly shows continued warming. The slight increases in the middle and base suggest that some heat is beginning to conduct downward, though the overall gradient remains steep, emphasizing the superior insulation at the lower sections.
3 Minutes 30 Seconds
80.8 °F – 67.4 °F – 66.3 °F
The top temperature continues its gradual climb while the middle sees a modest rise. The base remains steady, further indicating that the thermal energy is primarily concentrated at the top where the hot liquid makes the most contact.
4 Minutes
82.5 °F – 67.7 °F – 66.4 °F
At four minutes, the top reaches a clearly warmer state, now above 82°F. The marginal increases in the middle and base confirm that the insulation is still effective, preventing rapid heat transfer to the lower areas.
4 Minutes 30 Seconds
84.2°F – 68.3 °F – 66.8 °F
The top inches higher while the middle starts to show a slightly more pronounced warming. The base’s small rise to 66.8°F remains minimal, reinforcing that the majority of the heat remains near the top.
5 Minutes
85.1°F – 68.4°F – 66.8 °F
At five minutes, the top temperature reading increases. The marginal increases in the middle and unchanged base readings indicate that the heat transfer is beginning to plateau at the upper section.
5 Minutes 30 Seconds
86.2°F – 68.8°F – 66.9 °F
There’s a further slight increase at the top, suggesting that while the system is approaching equilibrium, the top still captures a bit more heat. The middle and base continue their near-steady performance.
6 Minutes
87.0°F – 68.9°F – 66.8 °F
At six minutes, the top shows a steady, incremental increase. The small change in the middle, with the base holding firm, underscores the tumbler’s ability to keep the lower regions close to ambient despite the rising temperature at the top.
6 Minutes 30 Seconds
87.7°F – 69.3°F – 66.9 °F
The gradual progression continues—with a modest further increase at the top and a slight rise in the middle. The base remains effectively insulated, highlighting the overall efficiency of the thermal barrier.
7 Minutes
88.4°F – 69.3°F – 66.9 °F
Seven minutes in, the top registers a noticeable warming, while the middle and base are virtually unchanged from the previous interval. This reinforces that the majority of the heat remains confined to the upper portion.
7 Minutes 30 Seconds
88.8°F – 69.4°F – 66.9 °F
A very slight incremental increase at the top is observed, suggesting the system is nearing a steady state. The minimal changes in the middle and base confirm the effectiveness of the insulation.
8 Minutes
89.2°F – 69.38°F – 67.1 °F
At eight minutes, the top continues its subtle climb as it approaches equilibrium, while the middle and base start to show a negligible increase—indicating that overall, the system is stabilizing.
8 Minutes 30 Seconds
89.6°F – 69.8°F – 67.0 °F
Stable readings are evident across all areas. The top’s continued slight increase is balanced by near-constant readings in the middle and base, showing that the heat distribution is now well-regulated.
9 Minutes
89.9°F – 69.8°F – 67.0 °F
By nine minutes, the top sees a marginal rise, while the middle and base hold steady. This suggests that the system is effectively maintaining its temperature gradient, with minimal further heat transfer beyond the top.
9 Minutes 30 Seconds
90.1°F – 70.1°F – 67.1 °F
The top reaches just over 90°F, marking the highest point in the upper zone so far. A slight increase in the middle is observed, while the base remains insulated. This indicates the tumbler’s insulation is effectively sustaining a controlled thermal gradient.
10 Minutes
90.3°F – 70.1°F – 67.1 °F
At ten minutes, the top temperature continues its subtle ascent while the middle and base remain essentially unchanged. The readings suggest that the system has largely stabilized with a clear, steady gradient.
15 Minutes
91.0°F – 70.7°F – 67.6 °F
The highest recorded temperature at the top occurs at 15 minutes, signifying that prolonged exposure has maximized heat absorption in that area. Meanwhile, the lower portions remain cool, emphasizing the tumbler’s effective insulation.
20 Minutes
90.8°F – 70.4°F – 67.4°F
At 20 minutes, the top temperature drops slightly from its peak, hinting at a gradual cooling or heat loss from the upper section. The middle and base maintain their near-ambient readings, further illustrating sustained insulation.
30 Minutes
90.1°F – 70.4°F – 67.5 °F
A continued controlled decline is observed at the top, while the middle and base remain stable. This indicates that, over time, the heat is slowly dissipating from the upper area, trending back toward equilibrium with the environment.
40 Minutes
90.1°F – 71.0°F – 68.2°F
At 40 minutes, the top remains steady while the middle and especially the base show a slight warming. This subtle rise in the lower zones may be due to residual heat gradually affecting all areas, yet the base still remains close to ambient conditions.


























Analysis & Observations
The IR imaging test provides valuable insights into the thermal behavior of the YETI Rambler 20 oz Tumbler:
- Distinct Thermal Zones:
The readings reveal a pronounced temperature gradient. The upper rim warms quickly due to direct contact with hot liquid, while the middle and base remain close to ambient temperature. This demonstrates that the double-wall vacuum insulation effectively restricts heat transfer to the rest of the tumbler. - Rapid Initial Response:
Within the first minute, the top temperature jumps significantly, indicating a rapid response to the heat source. However, the minimal change in the middle and base confirms that heat conduction is largely confined to the upper section initially. - Gradual Equilibration:
As time progresses, the top continues to increase until reaching a peak at around 15 minutes (91.0°F). Beyond this point, a slight cooling trend is observed, suggesting that the system begins to lose heat gradually while stabilizing towards equilibrium. - Consistent Insulation:
Throughout the test, the middle and base maintain near-ambient readings, underscoring the tumbler’s robust insulation. Even at 40 minutes, although there is a slight warming in the base, it remains significantly lower than the top, ensuring a comfortable handling experience. - User Considerations:
The effective insulation is a double-edged sword; while it prevents unwanted heat transfer to the hands, it also means that those seeking a warming effect from holding a mug might not find this design ideal.
Overall, these observations confirm that the YETI Rambler 20 oz Tumbler excels in maintaining a controlled thermal environment, offering both performance and safety when handling hot beverages.
Pros & Cons
Pros
- Effective Design: The secure lid and robust build minimize spills and enhance overall performance.
- Outstanding Insulation: The IR images confirm that the upper section warms as expected while the middle and base stay near ambient, making the tumbler comfortable to hold.
- Durable Construction: Made from high-quality 18/8 stainless steel, the tumbler is built to withstand everyday use and outdoor challenges.
Cons
- Exterior Stays Cool: Those who like to feel the warmth of a mug while drinking a hot drink may be disappointed, as the exterior surface temperature stays relatively close to ambient.
- Liquids Stay Hot For Longer: Your favorite coffee or tea brewed at 190 °F – 212°F will take longer to cool to ideal drinking temperature (usually around 140 °F) compared to ceramic or double walled glass.
- Premium Price: YETI’s products come with a higher price tag, reflecting their quality and performance but potentially limiting budget-conscious buyers.
Final Thoughts
The IR imaging test on the YETI Rambler 20 oz Stainless Steel Vacuum Insulated Tumbler clearly demonstrates its ability to insulate. This controlled heat transfer confirms that the tumbler’s double-wall vacuum insulation is highly effective. Despite a warmer upper rim when filled with hot liquids, the overall performance and durability make it a top choice for anyone seeking reliable temperature retention and robust construction.
For those who value both functionality and longevity in their drinkware, the YETI Rambler 20 oz Tumbler stands out as a premium option that lives up to the brand’s reputation.
Have Questions?
Drop them in the comments below! And if you’ve used the YETI Rambler 20 oz Stainless Steel Vacuum Insulated Tumbler in real-world conditions, share your experience. We’d love to see how it performs for others!
Disclaimer: This review is not sponsored by YETI. All observations and opinions are our own, based on personal testing and infrared photography.