Spark plug replacement and gas mileage
12-02-16, 04:05 PM
#1
Lead Lap
Thread Starter
Spark plug replacement and gas mileage
I currently have 127,500 miles on my original spark plugs. After almost 7 years of ownership with my 2001 LS430, the car drives like a dream with no current issues at all. Idles and accelerates smoothly. When I asked my trusty Indy mechanic, he suggested changing the plugs so that I might avoid any coil damage due to spark plug gap changes. The recommended plug change is 120,000 miles so I'm at that point. Here's my question. I will change the plugs soon, but can I anticipate any change is gas mileage?....even 1-2 mpg better? My yacht is not a Honda Civic and I'm aware of it and I've been getting in the low to mid teens for 95% city driving the last 7 years (13-15mpg all city). Any chance it might get better? For those members that have replaced their old plugs what do you think? Just curious, as I'm replacing them for preventative issues down the line anyway. Thanks all.
12-02-16, 04:56 PM
#2
my first LS430 i didn't change plugs until 175K miles and they still were great. Didn't notice any gas mileage change at all. Could have felt a little smoother idle but that might be just my head.
12-02-16, 05:51 PM
#4
Lead Lap
Thread Starter
What was the exact part number for the OEM spark plug replacement? I've read so many different numbers. Are they Denso Iridium IK20 or Lexus Part number 90080-91200 or Denso SK20R11 (3297)? Are these all the same? I want the right part number as it does take over an hour to replace. Thanks all.
12-02-16, 05:52 PM
#5
Lead Lap
Thread Starter
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12-03-16, 08:49 AM
#8
Lead Lap
Thread Starter
Thanks BigBruiser and everyone else for their experience changing the plugs. I guess it's more of preventative maintenance than any change in performance. Just now ordered the Denso SK20R11 from Rock Auto after verifying with Lexus that this is the same as their part number.
Last edited by Bocatrip; 12-03-16 at 09:35 AM.
12-03-16, 03:45 PM
#9
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Another data point for Plugs: I just installed a new set of Denso SK20R11 at 150k last week ;
this 2004 LS had factory plugs which were NGK's. These were performing fine but I was presuming that Denso's were the factory plug and that is why I ordered them. Denso and NGK are both listed in my owner manual.
Best regards
this 2004 LS had factory plugs which were NGK's. These were performing fine but I was presuming that Denso's were the factory plug and that is why I ordered them. Denso and NGK are both listed in my owner manual.
Best regards
12-03-16, 03:51 PM
#10
12-03-16, 07:49 PM
#11
Driver School Candidate
Funny that your posting about this. I had the plugs done on mine this week while she was in the shop for a tune-up. While talking with the tech, he said that he could tell they were the originals but it didn't seem to be a problem. LS currently has 159k on her, so that goes to show just how strong these vehicle are. Side note, I was driving my M3 while the LS was in the shop, and the M3 is now currently at the shop for cylinder failure for spark plug misfire. M3 is set up for track use, but man, I couldn't believe the irony of the situation. Preventative maintenance on my DD, and same issue shows up on the WW. Oh well, buck up and pay the piper as they say...
12-05-16, 02:58 AM
#12
Lexus Fanatic
I've never seen any benefit mpg-wise or other, in changing the plugs on my BMW or Nissan. I just did it when recommended. Although the last time on the Nissan, I went 100 when the interval is 60. They do wear out, but short of a problem with the motor, I doubt anything changes that a driver will notice. There are folks who insist their car is smoova when they use this or that motor oil. Placebo effect comes to mind IMHO ....
12-05-16, 06:27 AM
#13
@Bocatrip - I recommend you replace the spark plug tube seals as well. When I changed my plugs I noticed some oil residue on the coil over plug side of two of my spark plugs as well as oil residue on one of the tube seals. After some research on this forum I determined it was from old seals. I ordered 8 from Rock Auto and will install them when they arrive. Downside for me...I have to go back in and remove the tubes. Upside for you...you can install them when you change the spark plugs. 
At $2.00 a seal it is small change and preventative in nature.
BTW you don't have to remove the battery and/or battery holder for the #8 cylinder if you use a swivel socket.
At $2.00 a seal it is small change and preventative in nature.BTW you don't have to remove the battery and/or battery holder for the #8 cylinder if you use a swivel socket.
12-05-16, 06:39 AM
#14
No noticeable difference for me when I changed at 125K, now have 231K still averaging 23.3 MPG. Fuel computer has not been reset in at least a year. I will change again at 250K just so I have something to do in the garage.... Part # I used last time was 90919-01210
12-05-16, 07:54 AM
#15
Lead Lap
Thread Starter
@Bocatrip - I recommend you replace the spark plug tube seals as well. When I changed my plugs I noticed some oil residue on the coil over plug side of two of my spark plugs as well as oil residue on one of the tube seals. After some research on this forum I determined it was from old seals. I ordered 8 from Rock Auto and will install them when they arrive. Downside for me...I have to go back in and remove the tubes. Upside for you...you can install them when you change the spark plugs. At $2.00 a seal it is small change and preventative in nature.
BTW you don't have to remove the battery and/or battery holder for the #8 cylinder if you use a swivel socket.
At $2.00 a seal it is small change and preventative in nature.BTW you don't have to remove the battery and/or battery holder for the #8 cylinder if you use a swivel socket.
Last edited by Bocatrip; 12-05-16 at 02:20 PM.