I recently purchased a 1997 Lexus LS400, and I am interested in changing the plugs and wires. Does anyone have a recommendation on plugs? In particular, I was having trouble deciding between iridium and platinum.
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You might as well use whatever was originally on the car. Is the car due for a spark plug change? Do you expect to drive the car another 120,000 miles?
Are the wires defective? OEM spark plug wires can last well past 200,000 miles.
I had the original factory installed Denso iridium plugs on my 2000 LS400 replaced last week during the 120,000 mile service. The original iridium plugs don't show any sign of deterioration at 120,000 miles and the car doesn't run any better with the new iridium plugs.
The plug change interval is lower on the 97 LS400 -- probably 90,000 miles as it was on the 90 LS I had for a long, long time. The old platinum plugs on my 90 LS were in fine shape when they were changed at 90,000 and again at 180,000 miles. Toyota seems to design in a healthy margin between the recommended spark plug replacement interval and when the plugs start to deteriorate.
The switch from platinum to iridium spark plugs was what allowed the spark plug change interval for the LS400 to be extended from 90,000 to 120,000 miles beginning with the 1999 model year. This Denso webpage discusses this: http://www.densoiridium.com/faq.php
Jim - Lexus LS driver from 1990 to 2014 - Now driving a 2014 Toyota Sienna Limited with all packages and options including PCS, DRCC and VDIM
Your comments are very helpful. I am pretty sure the wires are shot, but the plugs were replaced about 40,000 miles ago. The current plugs are double platinum. Considering your experience, would you suspect that the plugs will last quite a while still?
copper plugs actually deliver a more powerful spark than platinum or iridium plugs (look up the conductance of platinum vs. copper for instance) but inversely copper doesn't last NEARLY as long as platinum/iridium plugs.
1. Black on Black 1999 LS400 PM-spec
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Yeah, that is true, most racing team run copper plugs. But what does a spark plug do.. it provides spark voltage to an already volatile mixture, does that mean if you apply a "bigger" or "smaller" spark is going to achieve any less of a result? I understand different metals are going to have different rates at which voltage is able to flow, but it doesn't mean that a copper plug isn't going to provide the same spark a platinum would. A race car motor is rebuilt every weekend, my Lexus hasn't been touched in a while. Just me.
The stock parts will do fine. I had Bosch platinum from the 60-120K interval. When I pulled them, they were still nice. I'd have used the factory plugs, it was just that this one particular shop had 7 so I'd have to wait a few days for more to come in. They had the Bosch platinum in stock so I went with them again. Some may eek out a bit more though for me this barge still pulls about 22-24MPG with my usual mix.
Exactly.... and after reading it, it points out the number one factor of igniting the mixture is the plug gap. Again, copper produces more voltage, it needs less gap to jump, unlike platinum or iridium, needs a larger gap to increase the life of the plug. Again, most race setups run coppers. If you take a can of gasoline and dump it out on the ground. You have a lighter and matches, they both yield different burning temperatures, but they will both easily light the gasoline on the ground. Is one better than the other... Yes, because with matches you can stand back, where as a lighter needs to be right up next to the gas.... Will one burn the gasoline anymore effectively than the other? That was my scenario, I guess...