hydrogenfu

ASking for 2015 AWD GS350. MAintenance schedule says to change at 96,000KM (or 60,000miles), but posts here say you can go well into 160,000KM (or 100,000miles).

What is the right interval to change spark plugs, and how much would it cost in Ontario?

AJLex19

The right interval is the one recommended by Lexus. Lexus makes these recommendations based on their own testing and tolerances. Although keep in mind that owners have had good, real-world experience with leaving the original plugs for longer than the recommended change interval without any degradation in gas mileage, engine smoothness, engine performance, etc.

If it makes you feel more comfortable and confident that you're following the guidelines of the manufacturer, you should change them at 60k. Note: I have a '13 AWD GS350 with 68k miles and have not changed the spark plugs.

peasodos

iTrader: (1)

Just do what the manual says. On the 450h it's change spark plugs at 100k miles. Not sure why Lexus has such a large difference on recommendations for basically same motor.

kolyan

As far as I understand it has something with emissions but plugs should be good for 100-120k

bclexus

Yes, if you want to maintain the emissions warranty through to 100k miles the spark plugs must be replaced. However the OE Iridium spark plugs are good for ¼ million miles or more without any degradation of performance or fuel economy.

GSDon

I just changed my plugs today at 95k and can tell you that they needed it so best to follow scheduled maintenance that Lexus suggests. The dealer near me quoted $600 US and it took me an hour and half change them. They were in there pretty tight so I put a little anti seize on the new ones. Not too hard to install with a little patience and you tube help. Good luck.

hydrogenfu

the difference in these 2 comments is exactly why I’m so confused on what’s the right interval to change 😂..

I don’t care about the warranty. But GSDon said they felt spark plugs needed change by 100,000miles (160,000km) from personal observation when they changed them..

bclexus

If you don't care about the emission warranty or if the car is getting close to 100k miles then there is absolutely zero need or benefit (in performance or economy) in replacing the spark plugs until the car has ¼ million miles or more on it.

93SCMax

That's a strong opinion.

Can you share photos of the 6 spark plug electrodes and threaded tips that have run 1/4 million miles or more in a 4th Gen GS? Can you also share the fuel economy and perceived engine response at that 1/4 million mile mark?

Thanks

bclexus

These images of original equipment DENSO Iridium spark plugs are said to be from the rear bank of a 2005 Toyota V6 (3MZ-FE) engine. They may not be from a Lexus 4th Gen 2GR 3.5L GS engine, but for the purpose of sharing information on original equipment Iridium spark plugs changed at 300,434 miles - a little over the 1/4 million mile mark - this should suffice to satisfy the most critically thinking or skeptic people to analyze facts and form a fair judgment.

From left to right, the spark plugs are for cylinders 1, 3, and 5 respectively. As you can easily see, the old Iridium spark plugs look 'about' as good as the new ones. The center electrode and gaps of the old spark plugs appear basically the same as the new ones.









Reference: ► Iridium plugs at 300,434 miles

93SCMax

Thanks for sharing. Interesting but not exactly what I asked for. These are not from a 2GR- engine, nor a 4th Gen GS, but from a much lower horse powered 3.3L V6.

They look amazingly well for 300K miles, but do not look "as good as new ones"...just check the center electrodes, the used ones are rounded and worn. The electrode gap certainly isn't to spec and I'd think performance and economy would be affected. Just my opinion based on these pictures.

Look, anyone can change their spark plugs at any interval they feel. The Toyota maintenance schedule recommends 60k miles. Even my Lexus dealer said you are safe to 100k miles. I did mine on my 3rd gen at 98k miles and am happy I did...better performance. For < $75 for OEM spark plugs and a few hours of my time, this was a no brainer. Every GS owner gets to choose. The OP probably appreciates varying opinions. My advice would be to change them prior to 100k miles if he hasn't had any misfire codes or performance issues up to that point.

Good luck to the OP. I can't comment on what it would cost in Ontario, but my dealer wanted $550 6 years ago and it was just so much cheaper and easier for me to do them myself.

bclexus

For those DIY people replacing their spark plugs themselves or purchasing new spark plugs for someone else to replace them, be aware of fake (counterfeit) spark plugs. Buying spark plugs on eBay is not recommended, and even some Amazon partner sellers are known to sell fake (counterfeit) products. Your best source is buying from a Lexus dealership.

93SCMax

I agree with you 100% concerning purchasing spark plugs from Ebay and Amazon. I've even had problems with Denso plugs from Advance Auto. I believe counterfeits got into their supply chain. My go to source is McGeorge Toyota in Richmond via mail order...last purchase was around $72 for 6 OEM Toyota spark plugs. Smooth running and no misfire codes since they were installed in 2021.

PGA71

iTrader: (3)

Here are Iridium plugs out of my 2013 GS350 Lux at 146K miles that I changed in January 2023.
Don't look as good as those 300K mi plugs, but car was still running like day one before and after change.

Not advocating when anyone should change or not change, just posting for information.




3 Passenger side Plugs


3 Divers side Plugs



146K plug vs New Plug

bclexus

@PGA71 - It looks like the original spark plugs were Denso P/N FK20HBR11. What Denso P/N did you replace them with? The new spark plug in your picture is Denso FK20HBR8, instead of FK20HBR11.