Engine Noise

[MK117]

GX470 2008 - noticed louder engine noise - not knocking- just engine RPM - thought it might be exhaust issue - had it checked at shop and nothing showed up unusual. Stated a few months ago. Wondering if using reg gas instead of premium could create louder engine ( using reg for last couple years) - but , again, No Knocking noise.- Different people in family have noticed the noise- The engine cover was missing after a service but was replaced. Any feedback?

[RX400h06]

A few thoughts that might help you piece this together:

1. Fuel Type: While the GX470’s 4.7L V8 is recommended to run on premium fuel for optimal performance, using regular gas typically won’t cause damage or knocking thanks to the engine’s knock sensors. However, it can slightly alter combustion characteristics, which might lead to a subtle increase in engine noise, especially under load or higher RPMs. So your hunch isn’t off base.
2. Engine Cover: That missing engine cover could’ve played a role too. It’s not just cosmetic—it helps dampen engine noise. If it was off for a while, your ears may have adjusted to a louder engine bay, and even after it was replaced, the perception of increased noise might linger.
3. Mechanical Possibilities: Since the shop didn’t find anything obvious, it’s worth considering:
   • Intake system: A loose or cracked air intake hose can amplify engine sound.
   • Motor mounts: Worn mounts can transmit more vibration and noise into the cabin.
   • Fan clutch or serpentine belt components: These can get louder with age and wear, especially if the noise rises with RPM.
4. Online Echoes: Interestingly, I found a nearly identical post from another GX470 owner describing the same symptoms—louder engine noise, no knocking, regular gas use, and a missing engine cover. So you’re definitely not alone in this.

If the noise hasn’t worsened and performance is steady, it might just be a combination of age, fuel, and acoustics. But if you’re still uneasy, a second opinion from a Lexus specialist or a mechanic with a good ear for engine tone might be worth it.

[MK117]

Great Info THANKS! 1 more issue I forgot to mention - when the shop checked for " noise" and could not find anything related , they did tell me I needed new Valve Cover gaskets on both sides as it was leaking some oil and a new new CV axle assembly on 1 side . Not sure if that is related but wanted to complete the post.

[RX400h06]

You're welcome!

I would think that those two issues would not increase engine noise.