I have a 1998 Lexus LS400 183,000 miles on it. I have never changed the spark plugs. It still starts perfect, runs great and still get good gas milage 26-27 mpg. Should the plugs be changed?


Asked by Jul 31, 2015 at 06:40 PM about the 1998 Lexus LS 400

Question type: Maintenance & Repair

All other maintenance has been done since I've had it.  It seems like I should change the plugs, but the car still starts and runs as good back in 2010 when it had 80,000 miles,  Gets about 26-27 mpg on the highway.

7 Answers


If the car runs,good,and gas milage is good,there is no need for the change,

1 out of 1 people think this is helpful.
Bob Beaman

Plugs should have been changed at 100,000 miles. The likely widened spark plug gap will put excessive loads on the ignition coils. The can damage the coils. Change the plugs and install what is recommended by the manufacturer.

2 out of 2 people think this is helpful.

Bob,may have a point,i say what i said,because you have no issue,and usually this age of car if you change them,be carefull not to damage the coils and wire boots,or you may be replacing some of them all so.

3 out of 3 people think this is helpful.
Bob Beaman

T_S_T, I almost always agree with you, but in this case not. You do give lots of good advise.

2 out of 2 people think this is helpful.

I use a high grade of oil and gas. I burn 93 octane (98% of the time) Exxon or Shell. Sometimes (91 octane) and (very seldom 89). It gets 26+ mpg on all of these grades of gas. This is such an amazing car.

Bob Beaman

Lexus does make one fine machine.


I also had a 1996 LS400 I bought in 2000. It had 33,000 miles on it. I did the regular maintenance on it. When I sold it in 2010, it had 175,000 miles. It ran, rode, and drove the same the day I sold as to when I bought it. Didn't change the plugs on it either. Amazing car!

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