10W-30 Vs. 10W-40: What's The Difference Between These Engine Oils?

If you're not a do-it-yourself car owner, then tackling relatively simple maintenance like an oil change can be daunting. It gets even more confusing when trying to decide which kind of motor oil you should use. 10W-30, for example, sounds very close to 10W-40. After all, how different can they be?

10W-30 and 10W-40 are indeed similar and can handle various high and low temperatures. The 10W rating means the oil is thinner and moves quicker in cold conditions. This is ideal when cranking the car on a winter morning before work. But the second number is where the difference lies.

The 30 and 40 refer to the viscosity, or measure of the oil's resistance to flow, at 212°F. If the number is low, it's thinner at high temps. This means that the 10W-30 would technically not perform as well as 10W-40 in the summertime. So, depending on your location and time of year, one oil might be a better choice than the other.

10W-30 and 10W-40 motor oil are a lot alike in terms of their ability to perform in a variety of temperatures due to the thinness of both grades. However, 10W-40 is slightly thicker, which means it protects your engine better in hotter weather. But what other differences are there between these two grades?

Fuel economy changes with each grade. Since oil creates drag inside the engine, you'd want to use a thinner grade so it increases fuel economy. This means the 10W-30 is the way to go. The 10W-30 is also typically less expensive and more available than the 10W-40, saving you money on your oil change.

However, if you're choosing motor oil based on fuel economy or cost, you may not be making the right choice. It's always best to consult the manufacturer for your car's oil, while also taking into account the time of year.