In our experience as automotie experts in the Houston area, we take pride in our ability to help our friend in the area with any questions they might have regarding how cars work. We understand, they are complicated machines, and some questions can’t be answered by simply looking in your owner’s manual. One question that seems to come up pretty frequently is how to know when to use 4×4 high s 4×4 low, and what the difference between the two settings actually is. First, however, we’d better discuss a fundamental misunderstanding that people have regarding four-wheel drive. Many people will turn on 4×4 every time they hook up a trailer to their truck, and this isn’t actually necessary. The key goal of 4×4 is to give additional traction, and in optimal conditions (and unless you’re in a tug-or-war or something), 4×4 isn’t going to substantially add anything of substance. But if you’re driing on slippery surfaces, steep inclines or unpaed roads or pastures, here’s where 4×4 is your friend. The ast majority of newer 4×4 systems have settings for “4-High’ and “4-Low,” while the “Auto” setting operates as a default setting. So, when the situation calls for better traction… Use “4-High” when… you are needing slightly more traction than normal, but can still drive at a reasonably high speed. If you’re going oer 15 mph, then this is the setting you’ll use. In snowy conditions or slippery conditions, rocky roads, or when you’re going oer some rough pasture, this is the setting you’ll want. However, you likely won’t want to go oer about 55 or 60 mph, because this can damage your transfer case. Use “4-Low” when… you need added torque because you’e got some tricky driing ahead. This is to be used when you’re driing under 15 mph, and in situations where you’re going through extreme ice, snow or mud; deep sand or water; doing a steep climb; or going oer extremely rough terrain. Generally speaking, if you can go oer about 15 mph, then you’ll want to be using 4-High instead.