What is the impact of switching from 5w30 to 5w40 on the engine?

[HaydenMarie]

There is no impact on the engine when switching from 5W30 to 5W40 oil for a car. The specific differences between 5w30 and 5w40 oils are as follows: 1. Different viscosity: 5W-30 and 5w-40 oils have different viscosities, with 40 being slightly higher, meaning the 40 oil has slightly higher fuel consumption. 2. Different performance at low temperatures: 5w-30 performs better at low temperatures because its viscosity is significantly better than 5w-40 under low-temperature conditions. 3. Different performance at high temperatures: Under high-temperature conditions, 5-40 has better stability.

[AllieLynn]

I used to use 5W30 engine oil, but later switched to 5W40. The biggest change I noticed is that the car's fuel consumption has increased. The engine's operating resistance has significantly increased, and the throttle doesn't feel as light and responsive as before, especially in city traffic jams. On average, I'm spending about 30-40 yuan more per month on fuel. However, the high-temperature protection has improved somewhat – during long summer trips, the engine noise is indeed reduced. My suggestion is that if you have a new car or one with low mileage, it's more cost-effective to stick with 5W30 as recommended in the manual. For older cars or those frequently carrying heavy loads on highways, 5W40 might be worth considering.

[IanMarie]

I recently tried switching from 5w30 to 5w40 engine oil. The most noticeable effect was that the engine sound became deeper. There wasn't much difference during cold starts, but it became particularly obvious after the engine warmed up. The RPM rises slower now, and acceleration response isn't as crisp as before. Fuel consumption increased by about 0.5 liters, with less difference on highways but particularly noticeable in city driving. Actually, it mainly depends on the vehicle's condition - my car has over 100,000 kilometers, and thicker oil film can help fill piston gaps to prevent oil burning. But I really wouldn't recommend this switch for new cars, as the OEM design compatibility is crucial.

[OMackenzie]

After switching from 5w30 to 5w40, I noticed the core impact is reduced fluidity. The 40-grade oil is thicker at high temperatures, forming a thicker oil film which indeed provides better protection at high RPMs, but at the cost of increased resistance. During cold starts, its low-temperature fluidity is the same as 30-grade oil, but the pumping resistance increases after warming up, leading to a 1%-3% drop in fuel economy. Long-term use may increase the burden on components like the camshaft, and new cars in particular should pay attention to oil return speed issues. It's best to check the engine operating manual before considering a switch.

[SanJames]

I find that using 5W40 instead of 5W30 in high summer temperatures gives me more peace of mind, as the oil film stability can withstand aggressive driving. However, the trade-off is slightly slower power response—there's always a delay of a fraction of a second when pressing the throttle. In winter, startup performance is similar, but fuel consumption increases by 0.3-0.7 liters after the engine warms up. I'd recommend it for those who frequently drive on mountain roads or own turbocharged cars, but for daily commuting, it's unnecessary—the factory-recommended viscosity offers the best balance.

[LaneRose]

After switching to 5w40, the most noticeable change is the heavier engine operation. The refined and smooth feeling has diminished, like running in a thick sweater. However, oil pressure is indeed more stable, and the high-temperature oil film strength is quite friendly for older cars. The fuel consumption increase is quite substantial, with my actual measurement showing about 0.4 liters more per 100 kilometers. Although the improved shear resistance extends the oil change interval, the power loss for new cars isn't worth it. Ultimately, it depends on the driving scenario—if it's long-term congested road conditions, the gains may not outweigh the losses.