Best spark plugs for 05 Prius

Chinese fakes from Amazon will grenade your engine

 

I very recently replaced both the plugs and coils on my V10 6.8 ltr Ford chassis motorhome. Near fell off my rocking chair at the cost, the plugs were more than the coils ...... but chalk and cheese on the first hill, and even on start up. The old ones had done 176,600 kms (roughly 110,000 mile).

Remember to put some thread lubricant on the plugs befor you install them, they will be there for the next 100,000 miles so you don't want the thread coming out with the plug .....
The gen 2 1500 goes for ever, if you look after it, my ex taxi Prius had 750,000kms on it, it wasn't the motor that took it off the road, needed parts for my other Prius on a holiday weekend where no one had front pads and rotors .... then the new NiMh battery got transferred to the other Prius ..... and that was about the end of it going back on the road ....

T1 Terry

 

Not knowing for sure if they’ve ever been changed, yeah change them. Instead of gambling to save a few bucks, get them from dealership or reputable, local auto supply place. Stick to the stock plug (spec’d in owner’s manual, and attached).

Repair Manual makes no mention of lube, and it complicates things, specifically torque.

You can check the gap, but the plug manufacturers recommend to not adjust. If it’s off they might have been dropped or something.

In particular when installing the new plugs, if you’ve got an especially grippy spark plug socket, it’s prudent to tape the extension to socket, otherwise the socket may stay on the plug when try to pull it off.

 

Non lubricated threads can affect torque reading, but not lubricated threads, the torque for tightening anything is based on clean lubricated threads ...... that includes wheel nuts/studs, lubricated threads or the taper being lubricated has nothing to do with the nut/stud remaining tight, it is the applied clamping effort and that can only occur with clean lubricated threads

T1 Terry

 

The threads on spark plugs (Denso and NGK, at least) are lubricated at the factory, so there should be no need to add more.

 

I just fitted 10 NGK Iridium plugs in my V10 6.8 ltr motorhome, and I can assure you, they were not lubricated from the factory ..... in fact, I don't think I've ever seen a pre lubricated spark plug, and I have fitted thousands, I had a dyno tune business for 12 yrs, 10 to 12 car a day through the dyno, 6 days a week, 4, 6, 8 cyl ..... that's a lot of spark plugs .....

T1 Terry

 

The lubrication is not noticeable, but the threads, for sure, are not dry.

 

Maybe just terminology tripping us up. If I google:

do denso or ngk recommend to lube spark plug threads

the AI summary commences with “No” and cites various reasons.

 

You're a bit behind the times with spark plugs. Absolutely DO NOT lubricate the threads of a spark plug when installing. The coating on the threads is specialized and no lube is required. here's an example from NGK. Other brands are similar.

1. Anti-seize

NGK spark plugs feature trivalent plating. This silver or chrome-colored finish on the threads is designed to provide corrosion resistance against moisture and chemicals. The coating also acts as a release agent during spark plug removal. NGK spark plugs are installed at the factory dry, without lubrication or anti-seize.

Anti-seize can act as a lubricant, altering torque values up to 20 percent, increasing the risk of spark plug thread breakage and/or metal shell stretch. Thread breakage can sometimes involve removing the cylinder head for repair. Metal shell stretch changes the heat rating of the spark plug and can result in serious engine damage caused by pre-ignition. Do not use anti-seize or lubricant on NGK spark plugs. It is completely unnecessary and can be detrimental.

 

If anti seize has been used previously, how would one clean the threads in the head without taking the head off? Can something like carb cleaning spray be used? Or just let it be and don't add any more AS compound?

 

Pragmatic first thought: any previous lube has long since baked to bone dry.

that aside, screw in an appropriately sized bottle brush, apply a couple of short shots of carb cleaner, then screw out the brush.