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2018 RX 350 Transmission Fluid Change - Is it really 'lifetime'?

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Rachel A. · rep 0 · May 22, 4:43 AM · 1 replies · solved · Question

Vehicle: 2018 Lexus RX 350 FWD

Hey everyone,

I have a 2018 Lexus RX 350, FWD, with about 75,000 miles on it. Lately, I've noticed the shifts feel a bit less smooth, especially when accelerating from a stop or downshifting. It's not terrible, but definitely different than it used to be.

I've heard conflicting things about transmission fluid. Some say it's a 'lifetime' fluid and never needs changing, while others recommend it around this mileage. What's the consensus for a 2018 RX 350? I want to keep this car running perfectly for a long time.

Has anyone done a transmission fluid drain and fill on their 2018 RX 350? What type of fluid did you use, and was it a difficult DIY job? Any advice would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:43 AM

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Hello Sarah,

It's a common misconception that transmission fluid is a 'lifetime' fluid. While it's designed for extended use, it still degrades over time and mileage, especially under typical driving conditions (stop-and-go traffic, towing, hot climates). For your 2018 Lexus RX 350, a transmission fluid service at 75,000 miles is a proactive maintenance step that can help restore shift quality and extend the life of your transmission.

Here's what you should know:

  1. Check Your Owner's Manual: Always refer to your specific owner's manual for the manufacturer's recommended service intervals and fluid specifications. Lexus typically recommends inspecting the fluid at certain intervals, and replacing it if conditions warrant.
  2. Fluid Type: Your 2018 RX 350 likely uses Toyota WS (World Standard) automatic transmission fluid. It's crucial to use the exact specified fluid to avoid transmission damage.
  3. DIY vs. Professional: A transmission fluid drain and fill can be a DIY job for experienced enthusiasts, but it's more complex than an oil change. It often involves specific temperature checks for accurate fluid level, and some models require a specific filling procedure. A full flush is usually best left to a professional shop with specialized equipment.

Causes of Rough Shifts & When to See a Shop:

  • Degraded Fluid: Over time, the fluid loses its lubricating and cooling properties, leading to increased friction and heat, which can cause rough shifts.
  • Low Fluid Level: A low fluid level can cause slippage and harsh engagement.
  • Internal Wear: While less likely at 75k miles with proper maintenance, internal transmission wear can also cause shifting issues.

If you're unsure about performing the service yourself, or if the rough shifting persists after a fluid change, it's best to have a qualified Lexus technician inspect the transmission. They can perform a diagnostic scan for any hidden codes and thoroughly assess the transmission's health.

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