The Mustang Forum for Track & Racing Enthusiasts

Taking your Mustang to an open track/HPDE event for the first time? Do you race competitively? This forum is for you! Log in to remove most ads.

  • Welcome to the Ford Mustang forum built for owners of the Mustang GT350, BOSS 302, GT500, and all other S550, S197, SN95, Fox Body and older Mustangs set up for open track days, road racing, and/or autocross. Join our forum, interact with others, share your build, and help us strengthen this community!

Which Spark Plugs to buy?

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

58
41
Exp. Type
HPDE
Exp. Level
Under 3 Years
Atlanta, GA
Sorry for dumb question. I've never actually replaced my spark plugs in any of my vehicles before...
There's so many spark plugs that 'fit' my vehicle, but I can't seem to pinpoint the differences between them.

Context:
My 2020 GT has 17k miles, powertrain is completely stock.
I've been running into random misfires only on the track, pretty much every session. I've been fueling up completely full at the beginning of the session which seems to have helped delay, but the eventual misfire before the session ends.

Many research here at TMO leads me to believe it may be fuel starvation on during high lateral G's, but just trying to check-off one thing at a time.

I'd appreciate it someone can just tell me "Hey, just buy these"

Thanks in advance!
 

JDee

Ancient Racer
1,818
2,020
Exp. Type
W2W Racing
Exp. Level
20+ Years
5 miles from Mosport
There's not much difference in spark plugs from quality brands. There's some off the wall stuff that claims magically better performance, but I've seen zero evidence they do anything in my 60 years of hanging around the track.
If you're getting misfires you should pull the codes from the computer, there might be something in there to point you in a direction.
I'd be inclined to think it's fuel starvation, my car suffers from that if it gets anywhere near half a tank. Run off the top half of the tank, I always top off before every session. And check for codes!
 
74
115
Exp. Type
HPDE
Exp. Level
Under 3 Years
West
When I was looking into the same, I had read OEM or NGK was the way to go for plugs. I went with OEM. I like to keep things factory where acceptable to do so. Plus they came pre-gapped (I still checked each one but no adjustments were needed.)

I went NGK and ditto.
 

Bill Pemberton

0ld Ford Automotive Racing Terror
8,526
8,588
Exp. Type
Time Attack
Exp. Level
20+ Years
Blair, Nebraska
Would agree with the responses , and with over 30 years in the Automotive business I can safely say changing plugs in newer vehicles is often a long range item - something that may be years and years into the future before they need switched out. Fuel starvation, on the other hand, is a known issue with the idiotic saddleback tank in the Mustang. Though later years are somewhat better, like JDee I don't let my tank get much below 1/2. I have already had two issues when I first got the Mach 1 where close to a quarter of a tank, I got hiccups and more.

Good luck and hopefully all the info put forth is somewhat helpful?
 
551
698
Exp. Type
Time Attack
Exp. Level
3-5 Years
SoCal
Not to derail the thread, but @Bill Pemberton what's the ideal change interval for spark plugs?
I know the manual says something like every 100k miles but many folks change them based on track hours or simply once a year. Mine looked healthy when I pulled them for the first time after 25k total (street & track) miles and roughly 15 track days.
Perhaps with further engine mods and more endurance-type track usage, the change interval goes up, but for a stock power, time attack car, maybe more time can pass between changing?
 
58
41
Exp. Type
HPDE
Exp. Level
Under 3 Years
Atlanta, GA
Okay thanks for the inputs,

Regarding the misfire:
Yes, I've been getting various codes from P0300 ~ P0308, both random and specific cylinders...
Dealership visits are useless since they can't replicate it during their test-drives (duh) and sends me home lol..

And yes, I've searched and read through lots of TMO threads regarding on-track misfires,
so I've been filling up the tank before every session, but 15~20 minutes into the session, I'm near half tank left, and comes the eventual misfire. I've never had a successful full 30-minute session :(



Regarding spark plugs,
Quick search yields a couple:
OEM Motorcraft SP589 ($3.39)/SP551 ($2.97)
NGK Laser Platinum LTR7CP13 ($7.86)
NGK Ruthenium HX High Ignitability LTR7BHX ($14.79)


So there's no difference in buying the OEM Motorcraft vs NGK's top of the line 'Ruthenium' ?
 

JDee

Ancient Racer
1,818
2,020
Exp. Type
W2W Racing
Exp. Level
20+ Years
5 miles from Mosport
The only way you're going to fix that fuel starvation issue is to go to a fuel cell or never let it get below 5/8th of a tank. I find 20 minute session is ideal, beyond that it's no man's land.
Depends on the track too, for example Mosport is a very fast power track so you use a lot more fuel and pull higher G loads there than on the twisty tight tracks.
 

Bill Pemberton

0ld Ford Automotive Racing Terror
8,526
8,588
Exp. Type
Time Attack
Exp. Level
20+ Years
Blair, Nebraska
I don't think there is a magic number on time, but often if the car sits a long period or is only raced, it is good to just check occasionally. We saw plenty of cars come in at 100K and the plugs still looked good, but folks often decide to change when the mileage is high or if they sit a long time ...........plus see BS1's advice for why he changes plugs.
 

TMO Supporting Vendors

Latest posts

Buy TMO Apparel

Buy TMO Apparel
Top