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  • Replacing spark plugs, just rolled over 100,000

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 #235301  by hbk73
My 2000 300m has like 100900miles on it and im pretty sure its time to change the spark plugs. Im getting like 16.0 on the digital overhead reading, and about 14 when i compute it with my tripometer and gallons of gas put into the tank. The cost of the plugs is no issue, so i was wondering, what kind of spark plugs should i get?
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 #235304  by 300maximilien
I know you are new, but did you look over the other threads in this topic?

The consensus is NGKs with a few liking the OEM Champions put in base Ms and even fewer liking the Bosch


Obligatory post: You are due for timing belt and water pump 100K not wait severe engine damage is very likely
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 #235307  by 300man86
I would also clean that throttle body to.
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 #235312  by LUNAT1C
Advance Auto Parts: NGK Laser Platinum 7781 as I recall.

I just installed those on my Special on Sunday. Funny enough, that's exactly what came out of my 02 Special's engine, and I'm certain they're the originals. I replaced mine at 91,600 miles. They were worn, but weren't too bad. I probably could have got another 5-10k out of them without issue.
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 #236899  by DaleFicken
Just put Champion Platinum in my 300M base. I thought the car was running good before, I can definitely tell the difference. The old Champions that were in there looked original and were quite wore. Next up, synthetic oil in Grace!
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 #236909  by Brando26
Yep, NGK laser platinums.
 #237062  by gymracer01
I'm sure shocked at your millage! What do you do, run 80 in 2nd gear. MY 2001 will get 26+ mpg at 75mph with the A/C on. It has 166,800 miles and only had one set of plugs at about 110,000.
 #237412  by hbk73
I do 100% in town driving, with AC on, so that may explain my milage, plus im 17......
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 #237426  by LUNAT1C
16 sounds about right for pure city driving. That's what my Special gets, pure stop'n'go.
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 #237452  by 300maximilien
Agreed. I drive all city and I am a spirited driver. In my old Special I would average 17ish in this '99 I am averaging 19.5.
 #240610  by hbk73
I replaced them, and now im getting about 16.7 on just in town driving, and the preformance is noticable.
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 #240616  by 300man86
HBK73 wrote:I replaced them, and now im getting about 16.7 on just in town driving, and the preformance is noticable.
Clean that throttle body too and dump a bottle of fuel injector cleaner. try Lucas fuel system treatment. Should be getting around 17-17.5 after that. But also winter is here so you may not have much more of an increase.

I average 21-22mpg long about 50% in town 50% highway about 100 miles a day.

87 20.5-21 mpg 93 21.5- 22.5mpg
 #250674  by isrb710
After reading this post, I decided to check one of my plugs to see how they were holding up after 85k miles. The plug looked OK, but I regapped it back to spec (.050 inches). I measured the gap on 5 of my 6 plugs. It varied from .062 to .068. All 6 plugs looked pretty good except for the gap. It seems to run a little better now. I'll watch the EVIC and see if my average mpg goes up any (22.3 now). I do about 50 % highway driving and I do NOT have a lead foot. I'll probably change the plugs at the 105,000 mile interval as the manual suggests. I'll install the Champions, since they're half the cost of the NGK's and seem to be liked just as well. ($3 vs $7 at Advance Auto Parts yesterday)

More importantly, I will plan on re-gapping new plugs after they get 50,000 miles on them - so they don't get so far out of spec.

fyi - I have one of the wire gauge plug gappers and it has a bending tool built into it that makes it REAL easy to gap the plug without pushing down on the middle electrode.