Should Engine Oil Be Thin or Thick?

[ReedFitz]

Engine oil tends to thicken over time. The main reasons are: 1. As time passes, the oil becomes increasingly viscous: transitioning from clear to cloudy, and the accumulation of impurities naturally increases its thickness. At its extreme, it can turn into a thick, asphalt-like consistency. 2. Oil thinning to a water-like consistency: Thinning of oil can indeed lead to excessively low oil pressure, resulting in semi-dry or dry friction between various engine components. Here is some additional information: 1. Introduction and functions: Engine oil, also known as motor lubricant, serves to lubricate and reduce friction, assist in cooling, seal against leaks, prevent rust and corrosion, and provide shock absorption for the engine. It is often referred to as the 'lifeblood' of a car. 2. Composition: Engine oil consists of base oil and additives. The base oil is the primary component of the lubricant, determining its fundamental properties, while additives compensate for and enhance the shortcomings of the base oil, imparting new characteristics. Additives are a crucial part of the lubricant.

[CharlotteRose]

For my old Accord with 100,000 kilometers, I use thicker oil like 5W-40. Older engines have larger component gaps, and thicker oil can better fill those gaps, reducing wear and noise. But for the new hybrid Lexus I bought my wife last year, the dealership directly used ultra-thin 0W-20 oil. Modern engines have higher precision, so thinner oil flows faster, cools better, and saves fuel. Last week, my neighbor insisted on using 0W-20 in his old Tiguan and ended up burning oil. So it really depends on the car's condition. Mechanics always say not to just look at the viscosity rating—cars that are frequently driven hard or often go on mountain roads actually benefit from thicker oil for better protection.

[VonDakota]

In summer when hauling loads with a pickup, I definitely opt for thicker motor oil. Last time during a 40°C heatwave while towing on the highway, the oil temperature on the dashboard nearly hit 120°C—thankfully I was using 10W-50. Thicker oil holds up better under extreme heat; the oil film is less prone to breaking down. But in winter, my wife’s Fit uses 0W-20—it flows like watered-down honey during subzero starts, lubricating the engine instantly. Once I forgot to switch to winter oil, and the dry grinding noise during cold starts was heart-stopping. Remember: the oil cap’s viscosity rating is your best guide. Most German cars demand 40-weight oil, while Japanese and Korean models are trending toward 20-weight these days.

[VonAlaina]

Anyone who's into car mods knows that turbocharged cars must use thicker oil. My tuned EA888 engine sees turbo temperatures hitting 600°C easily, where 40-weight oil just barely coats the bearings. Naturally aspirated cars have more flexibility—my MX-5 runs on 20-weight oil, smooth as butter at high RPMs like it's greased up. But before hitting the track, I temporarily switch to 50-weight since oil film pressure triples during sustained 7,000 RPM operation. Newer cars are even wilder—engines with cylinder deactivation use 0W-16 oil, seemingly watered-down yet saving 3% in fuel consumption.