Spark plug replacement - miles or years?

welcome!
yes, it was unnecessary and overpriced. still, in the scheme of things, not horrible, and one less thing to do down the road.
with that kind of mileage, watch your 12v, and save your money for a new hybrid battery

 

For what it's worth, the Toyota Warranty and Maintenance Booklet says to do the service at 120,000 miles or 12 years, whichever comes first.

 

Toyota part number: 90919-01275
Denso part number: SC16HR11

US online dealership source ($8.94 apiece):

2008-2019 Toyota Spark Plug 90919-01275 | McGeorge Toyota Parts

So $40~50 with shipping, or about the same through a local dealership.

Maybe an hour's labour, all the rigamarole of removing the wipers, wiper motor and cowl, before you even get around to the plugs. Maybe 1.5 hours?

Not sure.

 

We’ve done this job in under 45 minutes at a meetup.

And the next one will be in a shop.

Maybe with better tools it’ll go even faster.

 

It might have been a little early to replace the iridium spark plugs based upon length of service. I would have changed them at 12 years, just so that they don't get totally frozen in the cylinder head.

Yes, $261 is a high price but that is typical for Toyota dealer service pricing. If you DIY the four plugs would cost around $40.

 

Spark plugs don't age out, they wear out from use. No organic parts to crack or deteriorate, unlike hoses, tires, belts and suspension bushings.

Your dealer up sold you. Take it as a lesson learned and in the future just follow the maintenance schedule with either DIY or a good independent shop.

 

See post 7...plugs wear from use not age.

Many manufactures suggest plug inspection at 5 years.
The reason is to prevent electrolysis metal bonding between the head and the plug.
In other works, break the plugs loose, a step further remove check gap and condition, re-install.
From above posts Toyota is say 12 years, well, different from other maker recommendations.
Easy DIY (have proper tools) and I would still say 5 years out of conservatism.

Noting plug technology has changed and the metals used now a days may not have that bonding issue.
And if you do go through the labor to inspect the plugs, with the time invested it could be beneficial to spend $40 and install a new set of plugs.

Use a torque wrench for final tightening and di-electric grease in the boot caps and a tiny amount of anti seize on the plugs threads. If the plugs are hard/ stuck to remove, spray some Liquid Wrench onto the base of each plug to remove any rust, let the chemical soak by waiting a day, then start the engine and get it a little warm (not hot) to loosen any carbon buildup on the combustion chamber end of plugs. Those would be my tips.

Good luck.

 

Mostly miles.

I say mostly because there's a growing number of people who have taken to camping or even living in their Prius full-time, and the odometer won't reflect that usage even though it is wearing the plugs.

 

I've changed a lot of spark plugs and have never had one sieze, in either cast iron or aluminum heads. I just swapped an original set on a 2007 Camry with 145K miles. Popped right out.

There is no compelling reason to pull plugs every 5 years for inspection. These are pretty much a "work or don't work" item. If the car is running well, then the spark plugs are doing well. I would pull them early only if there were problems that could be related to the spark plugs.

 

There are more than 50 now?

 

Don't mistake it for enthusiasm, but I have the sense that it's a lot more than 50.

 

If you're living in your Prius, you are essentially homeless, so I suspect regular spark plug inspection would not be high on the to-do list.

 

Yeah but 12 years? That's a goodly stretch. Besides the possibility of them seizing, pulling the plug might alert you to engine issues. And if you DIY, it's $40.

 

The plugs themselves can go 150,000 miles. It is the emissions warranty that "requires" the 120,000 mile change in most (non CARB) states for 2010 models.

A footnote in the 2010 Prius maintenance manual "Maintenance services of spark plugs are required under the terms of the Emission Control Warranty. For vehicles corresponding to PZEV for California, Maine, Massachusetts, New York and Vermont, replacement interval is 150,000 miles."

For current year Toyota hybrids, the 150,000 interval is for "PZEV vehicles" but they don't state clearly whether that applies to all Pri or just in some states.

So, what happens if you go beyond 120,000 miles?

In my state of Colorado, which was not a CARB state in 2010 but is now, can I wait until 150,000 (2010 CARB interval) before changing?

I'll probably change at 120,000 miles anyway.

 

If you don’t change at 120,000 the CARB police will come and getcha.

My plugs looks pretty bad at 119,000 when swapped out. I wouldn’t wait til 150,000, unless it’s a plug-in model with over half of the miles were EV.

 

As plugs age, the gap increases and eventually you get misfires.

 

When I looked at the Denso website a few years ago, the original equipment iridium plugs were rated at 120K miles. My guess is that the 150K mile change interval in CA is more for regulatory reasons and less because the underlying engineering allows that.

Unless you think that the gasoline in CA, ME, MA, NY and VT is better than the gasoline in the other 45 unnamed states.

 

Then there is the fact that our gas engines don't run for about 20% of those miles. (Still, I will change at 120,000)