Spark Plug Heat Range Explained. Hot or Cold Plugs?? 

Just a note, heat range and spark are independent. Colder heat range = colder ceramic = easier to foul at low speeds or rich mixtures, but the heat range doesn't affect spark blowout. Spark blowout is more related to things such as the firing end design (gap size, firing position/projection, electrode shapes), indexing, boost/compression ratio, combustion chamber swirl/turbulence, ignition system energy and high demand voltage (voltage needed to jump the gap). Generally speaking, if you have spark blowout with a plug and you switch to one heater range colder (all else being equal), you will most likely still have spark blowout. If it takes 24kV to jump the gap with a heat range 6 plug, it will also take 24kV for a heat range 7 plug. Because the spark and heat range are independent. The main thing to avoid is pre-ignition - where the ceramic is holding so much heat that it becomes the ignition point before the spark occurs- which is bad news. Melted plugs are the least of your worries then - melted parts in the engine is of course the worst...

NGK TR55 gapped .035-.045 for stock or mild modded 'all motor' engines NGK TR6 gapped .025-.030 for low boost less than 14psi or small nitrous 150 shot NGK-BR7EF gapped .020-.024 for high boost 18-26lbs big nitrous 250 shot "99% of the time I Use NGK TR6 plug, and I gap them at at least .025 to start, because I will nearly always shoot for 20-22lbs of boost, and if you gap them around 30 you will get blowout. we also use the BR7 EF plug when running higher hp, or over 14psi on cars without methanol, or if you just want to be super safe you can run it, fairly cold plug for low boost or low hp application, if you are in an area where its super hot or your compression is high etc might be a good choice"

Finally someone who can explain it well 👍

You are right on time with this one I was sitting here looking at plugs for my wife's gz250

Hello there Jeff. Man I love that Buick.

Cheers. Looking up this for a 70's dortbike with points. Nothing fancy but points are such a mission. Going for a hotter plug to keep the temp up in my low performance workhorse(honda xl 250 motorsport). I was worried as in NZ people say a hotter plug will melt the piston even in low performance, I didn't believe it and after a couple of videos your video teches easily what the other videos tried to tech, thanks for clarifying this so easily with that diagram and example. Churr, good luck with things

I bought 64 cc aluminum heads for my 350 chevy with dish pistons that made the compression about 9 to 1. I bought the recommended plugs which were NGK with 7 heat range. Come to find out they were way too cold and the plugs fouled coal black after a few miles. These head companies need a chart showing what plugs you should run with what compression. Mine only needed stock (hot) plugs with low compression.

Love the tech stuff you do. Keep it up! Great video!

like the spark plug info. now i know what it means. Thanks

Great video jeff,great explanation of plug heat ranges

Wow.. Great Video/ Info.. Ya don't hear anyone really address this. Would you suggest the NGK 5-series will be good for an 89 Vette, with only air flow and exhaust upgrades and smog and egr delete. Not boosted yet.

GREAT! I learned something new today. Thanks for this video..very nice

Wow what's up brother I worked on cars for quite a while back in the day not anymore I take it to the dealer LOL. But that's good to know definitely thank you very much

short and sweet thx mate

Thanks for the one o one class on that!👍

Thank you, your are a great instructor!!

thanx for this i have a 2014 chevy silverado 1500 with 5.3l .all i have are bolt and pretty much stock havent done any inside motor work yet. on and im gettready to order diablo preditor 2 platinum. what plug is suggested my end result is a p 1scs 1 procharger

Great info. +1 for the intro song!

Thank you. Good info. Helps with the choice.

Excellent explanation, thanks!

Thank you. Great video quality too!

Beautiful explanation

very helpful. thank you

Thanks for sharing This video help me a lot happy for your easy explane from 1 to 10 Have a nice day and stay safe Mark

Great video, I'm running a 1.4 liter turbo and stock boost is around 14 PSI Max. I currently have an after-market 93 and e85 tune full bolt ons pushing 21 psi. It's a daily driver driven spiritedly with no track days and no autocross. NGK recommend stock 7 heat range do you think a 7 will suffice or do I need to go colder to an 8? Thank you in advance

Very informative thank you for that

Nice job explaining!

I appreciate the info! 👍🏾

I changed 2 plugs in my 4runner that blow out in road trip and put cheap 3 dollar plugs in there get it going and my heat in my 4runner doesn't heat up good at all I think it's bec the 2 new plugs don't warm my engine good at all

Thank you so much for this. I just bought a step colder set of Ruthenium plugs for my Focus ST, stock map, but she has been misfiring, I also got some MSD coil packs that generate a more powerful spark, since I think my issue is related to a bad coil, figured might as well upgrade and get some of the touted benefits of higher mpg and efficiency improvements. The car runs 5-18psi out of a K03 Borg Warner Turbocharger depending on throttle input. Do u think this setup with the step colder (ltr7 instead of the stock ltr6) as well as the MSD is going to be bad for my engine long term, or help it last longer? Not looking for power gains, just wanna minimize knock and misfires. Worth noting the misfires are intermittent, and only happen on cylinders 1 and 3.

Perfect video, thanks for the clear information. What about adjusting plug gap from stock to high performance engines?

Every LS engine I’ve worked on runs iridium plugs, you got it backwards a hot plugs burns cleaner than a cold plug for a NoS or boost application you want the hottest plug you can get the hotter the spark the cleaner the burn the more HP you make I ran NoS for years with the hottest Autolites they made plus an HEI Distributer and a high fire coil never had a problem with cylinder temps you kids today have it backwards

I have a 1995 Blazer with a 4.3 vortec. It has been missing a lot on the # 5 & 6 cylinders. The compression is low on them as well. I’d like to squeeze a few more miles out of her before putting her out to pasture. I’m thinking if I run hotter plugs on those two cylinders she’ll burn better and help alleviate the unburned gas vapor in the exhaust. Does sound feasible? And how do I choose the hotter plug?

My car has recommended heat range 5 but no iridium plug is available. All are available in 6 heat range

Great video. What point on na ls engines do you consider changing plugs? I have 10.5:1 and I'm still using factory delco plug.

So for a stock 350 bored 30 over with headers a ngk 6 would be fine?

thanks although may be too professional. if user replace range5 plug with range7, or vise versa, what the effect? suppose car is designed w/o turbe and original is range5 plug.

Jeff, recommendation on a NGK heat range for a built gen V LT1 in a 2017 camaro ss. Compression is still the stock 11.5:1 and I will be running a 88/96 turbo on e85. Should be making around 1200hp. Awesome and informative video man. thanks.

Quick question I have a stock 454ss truck. My question is should I run copper plugs or can I run iridium plugs.

You said "Why don't you want your plugs to run hot? Because they will melt" I thought the danger was pre-ignition, especially in a blown engine, but really in any engine. In fact I just watched another YT video that stated this. Is that an issue?

stock 4.6L 2v... hotter plugs would work better? i have a bad coil and wanting to replace all coils with accel and go with NGK IX Irdium 3689 plugs

And here i thought hotter plugs were for lower rpms and octane, and colder plugs were for higher rpm and octane...

Thank you

you forgot about detonation... the main reason youd want a colder plug

Love that Buick but what about small Engines like snowblowers hot or cold if I use non oxygenated gasoline

So if I have a NA 5.3 vortec tuned for mid grade fuel I would want to run a 5 ?

can i use a hotter spark plug in one cylinder with low compression to prevent carbon fouling?

My vehicle specifies Denso SK16HR11 but the mechanic installed SK20HR11 which is colder then the recommended. What impact will it have on the engine and performance? Should I take the vehicle back and ask him to install the recommended spark plugs?

I have 350 engine the guy i bought truck from he told me when he built engine he used ac delco45 but i put egk plugs now when i pump gas peddle to crank truck it cranks and runs great i let truck run maybe 3min tops cause its in my garage but when i check plugs there wet can u explain why plugs are wet and truck is running great

Is it bad to run a colder plug when it isnt necessary?

Hey, I have a built 427 naturally aspirated big block In a 1970 Chevy Nova. I am wondering what spark plugs you would recommend to start with. The motor has around 500 hp. with a holly 850 double pumper.

I only drive 2 - 5 mi at time should i run. A hotter plug ?

I work in taxi engine runs 8 hours non stop, should I look for colder spark plugs ? Or type 6 bosch should be OK?

Great content. Now let's get that 8.8 in the back of that regal! :)

Hi, how to guess the correct gap, please? Mine is 11mm and i went to 0,9mm. Thanks.

you mean to tell me ls motors dont have to use iridium?

I have a f23a1 it had 3 irridium spark plugs and a autostate spark plugs lmao

That's 7pm?!

my E39 M5 should have the 6 in it but they only have 7 and up. You think it would be ok to put the 7 in it? oh and its supercharged not crazy but from 400hp to 550hp about 4-6lb boost. Also you dont really go into the cons of say running a 10 plug on a car that only requires a 4 plug, you went 1 way (with the plugs melting) but not the adverse effect going the other way extreme cold) and i live in a cold climate too (sweden)

I recently just turbocharged a joiner 1100 sand viper buggy it's running a little bit lean I'm only running about 8 lb on a small turbo but it means out can should I go to a colder plug would that help

I haven’t seen the question asked yet but with so many Ford ecoboost owners, which plug do you recommended for the 3.5L ecoboost?

Do u think I’ll be straight running my ngk tr6 with about a 100shot (dry) on my Lt1 bored stroke cammed fbo a1000 fuel pump and aero fuel pressure regulator

I appreciate you.

So is it bad to run a colder plug in a stock engine then?

But how much does heat range affect or cause more/less pre-ignition

I run a tr7 in my car right now with 10.5 compression and I will eventually be less boosted in e85

I have a 96 Camaro Z28 with the LT1. No idea what the compression is, or what it should be, but runs great still. What type of plugs should I run? While using a coil producing 40k volts+....

Have you ever cut your plugs apart and read them?

Good video

Thanks for the break down. From I gather, I need a 7? 5.3 with LSA. 2.45 pulley. Any feedback would be great. Also, what are your thoughts on the Brisk Silver Plugs?

Hi I have a Shelby gt500 5.8l supercharge stock. What kind of spark plug you recommend for my car?

good explanation but damn i like ur beard hahaha

I have a 1984 Plymouth voyager van with a 2.2,... since 2008 I have used Bosh Platnum Part number#4018 ,...WR8DP,.....no longer available,.....Now the Bosh replacement plugs are longer,......so I took them back. Then I got NGK GR4GP,...Stock Number 2763 they say Heat range 4? They are the right length. But will a 4 heat range melt the pistons?

You said too hot of a plug would melt in a hopped-up engine, so what would happen if you ran a cold plug in a stock LS?

Hey Jeff I got a 2012 VW bug turbo 2.0 .I have a plug that fouls in 30 days a ngkd6h905601a on cylinder 1 change coil twice .looks like i have oil coming and fouling plug any suggestions. 120k miles. Should I go hotter? I only drive it on close store runs help!

Getting dieseling on an '85 sbc 350. Currently has an ACD 1 spark plug, what plug would I use to possibly stop that from happening? I've already checked the timing & the distributor vac & weights. Going to try different gas but want to have an alternative just in case.

I have 1.4L Kia Rio. The 6 heat range oem plugs cost twice as much as 7 heat range from NGK seller. (Both plugs are NGK). Will that make my car weaker than it is right now?

The higher number means a hotter plug and the lower number means colder. In all spark plugs?

I have a 2011 Chevy Silverado V8 flex fuel, I have a mild cam and headers. I’d like to run E85 most of the time what NGK should I be running

Well sir I wish I have more Ls guy like you , cuz the one here just drank too much dexcool.

what about a 50cc two stroke?

Hi what ambient temperature are heat ranges based on? In hot climates is it better to run 1 heat range colder for NA engines ? Eg 5 to 6 for NGK plugs ?

I was wondering why is it that most of the videos I watch are about NGK?

What do you think on the e3 spark plugs? And engine coils

So the exposed porcelain creates turbulence which promotes blowout?

I have a stock 08 lexus and which spark plugs will make mu car go faster

I ran too much octane booster that has MMT in it and it turned all of my plugs orange? Can I just run premium gas here in CA and will that shit burn off?

I thought that the point of cold plugs are to prevent donation

tell us more about your hydro boost set up, astro van?

Tapered=iron head Gasket = aluminum head to seal

What spark plug you recommend for my 6.2 l92 headers, cam? Tr55? Or tr6? Thanks

i am just looking for stock plugs for stock engine come on.

Hi! I'm driving a 2007 Audi S8 which has an ECU remap. V10, 5.2 L. 450 HP stock. Probably around 480 HP now? The factory installed double Platinum plugs. I'm wondering if it's safe to install single Platinum plugs instead. I've tested the car and it runs great, starts better too. Just concerned with the heat range. What do you advice?

NGK is like AC then . champion number goes up hotter it is then

gap filler for bmw engine m54b25 ? ❌

In running 11.5:1 6.0 ls with tr6s thinking about going to 7

What about E3 spark plugs what heat range are those?

Do e3 make colder plugs

Why do you and John not make videos anymore

What plug would you recommend for an 89 l98 5.7 iroc with a 480/501 cam Stock tpi with 22 lb injectors?