Which Lenovo Thinkpads are compatible with 65 Watt, 90 Watt or 135 Watt adapters?
A general rule of thumb is if your laptop is shipped with 65 watts adapter, then you can use either 90 watt or 135 watt adapters. You can generally use a more powerful adapters than required, but use of lower rated (than required) adapters may lead to improper system performance and operation.
This article references adapters that share the larger barrel connector and 20V rating that were introduced begining with the T60 / R60 / X60/ Z60 series systems. These adapters feature a slightly higher voltage 20v vs 16v, and a larger diameter barrel making them non-interchangable with prior ThinkPad adapters used on T43, R51, X41 and earlier model IBM Thinkpads.
In the photo below, the newer 20V adapter style plug is shown on the left and can easily be visually differentiated from earlier 16v adapter design shown on the right. Many IdeaPad models use a similar looking connector to the version on the right, but they operate at a higher 19v or 20v level and cannot interchange with earlier ThinkPad adapters.
1. If your laptop has a discrete GPU (which are the ATI and Nvidia GPU) and not the Intel GPU (which is normally shipped with 65 watts adapter (but sometimes they are shipped with 90 watts in some countries), then you should use either 90 watts or 135 watts adapter.
2. When 65 watts adapters are used with the laptops using a discrete graphics card, the laptop may throttle down to prevent overdrawing of power from the lower specification adapters (laptop Power Management knows whether you have the 65 or 90 watts adapters connected). This will result in reduced system performance, and potentially longer time to charge the battery, especially while the system is powered on. While, there is a safety mechanism in place, the higher demand could cause the 65w adapter to run at higher temperatures.
3. You can use the 135 watts adapter on Lenovo Thinkpads that use either the 65 watt and 90 watts adapters without any problem. However do not use your W510 with 65 watts and 90 watts adapter. Some model of Thinkpads will recognise the 135 watts adapter as 135 watts, while other may recognise it as 120 watts or 90 watts, but it doesn't affect the functionality.