These Are The Biggest Downsides Of Using Thicker Engine Oil In Your Car

Engine oil is a crucial component of just about every engine, and it needs to be replaced regularly, according to the manufacturer's recommendations, to ensure the engine is working as it should. There are various kinds of engine oil and various classifications, each with its own suitable application, but the most important designation is the viscosity rating. For example, 5W-30 oil has a viscosity rating of five at low engine temperatures and 30 at higher temperatures. The lower the rating is, the faster the oil will flow in the engine at both lower and higher engine temperatures. 

Ultimately, it all depends on the type of engine, the kind of vehicle it powers, and, crucially, the engine oil the manufacturer recommends. That being said, let's say you wanted to use thicker oil than what is recommended. While it might offer benefits, such as increased oil pressure, there are several reasons it might not be a good idea.

As mentioned, one benefit of thicker engine oil is its contribution to higher overall oil pressure, which can be helpful if your car has low oil pressure issues. However, if the oil is thicker, especially if it has a higher W rating, lubrication will be significantly slowed. Thicker oil takes longer to lubricate the necessary components, and when the engine isn't lubricated properly, it leads to increased, accelerated engine wear, not to mention a loss of power.

A lower-viscosity oil also means less internal friction, so using a thicker oil increases friction, which can be detrimental to fuel economy. Thicker oil can also oxidize and form sludge because its reduced flow inevitably leads to higher temperatures, further straining the engine. Some other downsides include worse cold-start performance and increased strain on the oil pump, which could accelerate wear and lead to premature replacement.

That said, it's not all bad news. Some notable benefits of using thicker oils include reduced consumption and improved sealing, which can be helpful for high-mileage engines that have leaks. What's important to remember here is that if you do decide to switch to a thicker engine oil, make sure the viscosity difference between the old and new oils isn't huge. Say you've been using 5W-30; switching to 10W-30 won't be too detrimental and won't make a massive difference. Even then, it's always a good idea to stick to manufacturer recommendations for both viscosity ratings and replacement intervals.