How to verify OEM spark plug compatibility Prius Gen3

DO NOT purchase spark plugs from ebay or amazon. There are just too many counterfeits out there.

get the 3444 plugs from RockAuto.com they're less than $10 each and will be actual denso plugs, not some chinese imitation.

 

I used the twenties in my cars down here in the southeast United States where it's really hot most of the Year always have most all toyz come w 16 HR or did forever . I always used the 20 since working at dealer down here . I use the long life model of whatever plug series I'm using at time denso. Makes a bunch . Fine wire racing etc .

 

Can't remember where I heard it, but the story was the 16's are a slightly hotter plug, ie: they'll burn off deposits better. The owner's manual says 20's, but Toyota revised, presumably due to plugs building up deposits. I had the 20's for 12 years, looked virtually new when I pulled them after 12 years (and 95k kms), replaced with the 16's, per Toyota's recommendation.

I'd just go with the Denso 16's, that's the recommendation.

Sort of the exception, but this time round the dealership parts department was actually cheaper than my usual local automotive go-to place. Are you near a dealership?

 

Good price, but maybe counterfeit?

FWIW, I paid $16.50 CDN apiece for mine, in 2022, through dealership. The Toyota part no (it's the denso, just in different box) was 90919=01275.

 

lol at $4 a plug they're guaranteed to be counterfeit.

 

Choosing a hotter plug improves burning off of deposits, at the trade of a lower safety margin from pre-ignition (the hotter plug tip may ignite the mixture before the spark is timed to occur). That's what makes the choice a trade-off, and not just a simple "get hotter plugs, they'll stay cleaner" rule.

The language and the numbering are tricky. Denso uses lower numbers for hotter-running plugs (so 16s run hotter than 20s). Some other manufacturers use an opposite numbering convention.

Denso uses the term "low heat range" (and a low number) to mean slower heat dissipation toward the plug shell—meaning a plug that stays hotter. They use "high heat range" (and a high number) to mean faster heat dissipation toward the shell, meaning a plug that runs cooler. So in Denso literature, "low heat range" means a hot plug, and "high heat range" means a cold plug.

NGK avoids that mess by not even using terms like "low heat range" or "high heat range"—they say "hot heat range" or "cold heat range" (respectively!), instead.

Heat Range | Basic Knowledge | SPARK PLUG | Denso

Understanding Spark Plug Heat Range - NGK Spark Plugs

 

If plugs are like pics they look purdy good the lettering on the silver . But that's a show pic. And they're 15.99 a pop

 

Just be careful about "senior members". Some want you to believe the know everything,
and they are never wrong. If you disagree with them, they will attack you.

Sticking with the OEM is a good idea, can't really go wrong.

Buying from ebay or amazon, it's extremely likely they are cheap chinese copies, and won't last.
That's why they are cheaper.

Buying from autozone, or similar auto parts store it's less likely that they are cheap copies.

I've been using Bosch plugs without any issues. But the last time I changed them they were
out of them, so I tried ngk. 1 failed after about 2000 miles, and possibly a 2nd one also.

I think Toyota went to the hotter plug to help offset the oil burning. It really won't hurt to use it,
but using the original one will work fine.

Every manufacturer uses different countries to make there parts. Some have strict standards and
even if they are make in china, they use the correct parts and tolerences. It's when the chinese
COPY them, and use cheaper components and don't care about tolerences is where the issue is.

 

I just replaced the original spark plugs on my 2015 with 99.8K miles, which were Denso SC20HR11, and replaced with Denso SC16HR11 purchased from Amazon. The price was $49 plus tax for four so I hope they are not counterfeit.

The Denso website shows SC16HR11 as the correct choice for the 3G Prius.

The old plugs had some deposits on the ceramic tip and the porcelain tail had a narrow brown band where the porcelain is left exposed by the coil socket that fits over the plug. The amount of deposits on the tip was sufficient so that I think a hotter-running plug is appropriate for my environment.

I understand that narrow brown band is a corona stain caused by high voltage ionizing the air and causing oil or dirt particles to adhere to the exposed porcelain. This is supposed to be a normal phenomenon and does not imply a problem with the plug or coil.

I hope the OP understands that the wipers, black plastic cowl, wiper motor and sheet metal tray will need to be removed as pre-requisite to pull the spark coils out of the cylinder head. That is not a difficult job but will take another 40 minutes to an hour to remove and replace.

 

My bet is they are cheap chinese copies......

I don't have the link, but they guy from illinois that is a toyota guy did a program on how to
spot the cheap copies.
Hopefully, someone will have it and can post it.

 

Excellent @NutzAboutBolts video on 3rd gen spark plug access:

BTW, it's video #13 , here:

Nutz About Bolts Prius Maintenance Videos | PriusChat

One quibble with the video: he puts a generous coat of anti-seize on the new plug threads, and says to torque to 20 ft/lb. Repair Manual specs 15 ftr/lb, and no mention of lube, so presumably clean/dry threads.

For a torque value that low, a 3/8" or 1/4" drive torque wrench is appropriate. The latter typically uses inch/pounds. If you have a value like 8 foot/pounds, that is equal to 96 inch/pounds (8x12).

Further on inch versus pound torque values, I've lost count of the reports here, novice mechanics see the torque value for the spark plug coil hold-down bolt, gloss over that it's inch pounds, get out the 1/2" torque wrench, set it to foot pounds, and consequently snap the head off, leave the bolt fragment stuck. Suffice to say: reserve the torque wrench for the spark plugs, just use common sense on the rest of the fasteners you encounter.

Regarding lube on the threads, try googling: "denso recommendation for anti-seize on spark plugs". The AI summary says Denso, and others, are against it.

Repair Manual excerpt attached, and another quibble, regarding that publication: the spark plug section makes NO mention of the torque value for the plugs, I found that about a thousand pages distant, lumped in with the valve cover removal, which makes no sense. Anyway, tacked that page on, at the end of the excerpt.

 

IDENTIFY COUNTERFEIT DENSO SPARK PLUGS

 

I agree there is no need for anti-seize especially since these plugs have such a small threaded shell diameter. I had absolutely no issue removing the original plugs that had been sitting there for 10 years. With 2G Prius, I recall the plugs had some reluctance to come out after such a long service duration.

 

Tried googling:

does denso coat their spark plug threads with a lubricant

and again, AI was very helpful, saying in part:

Denso spark plugs (and NGK) come with a special trivalent plating on their threads that acts like a built-in lubricant

Regarding counterfeit plugs, simply purchasing from dealership, or reputable, local, brick-and-mortar automotive specialty shop, should improve the odds of not getting burned. Again, I went with dealership (at the 12 year mark), they were lower priced than my go-to third party store, but that place is always first on my list; they're very hands-on, sell specialty tools, have a machine shop section, can sell you stuff like fuel line by the foot, and so on.

This is something you do every 120k miles or 12 years, not worth gambling.

 

^ This. Don't take it lightly. I was in a traffic slowdown the other day because an ambulance was loading in somebody who'd been attacked by a senior member he'd disagreed with. It was grisly.