I'm going to be commuting back and forth on the interstate for a few years and was wondering what type of spark plug would be best. I've heard there are hot types and cold types. When I bought my first set from Napa, they gave me the NGK BR9EQ14 cold-type. Is this suitable for my type of driving?

 

yep, you'd usually want cold for the highway, hot for the city. Some of us run the colder FC/FD trailing plugs in all 4 positions, the platinum ones also last longer than the usual.

 

Why do they call them 'hot' and 'cold'?

 

this is from the mazdatrix website

A common misconception of many people are the terms "Hot" spark plug, and "Cold" spark plug. The temperature rating of the plug refers to the running temperature of the physical spark plug - i.e. a "Hot" plug will retain more of the combustion heat in the plug itself, meaning not transfer the heat to the engine itself. This is why a "Hot" plug is needed for slower city type driving so the carbon deposits will be burned off the plug, and clean firing will still be possible even when combustion temps are low (idling, stop & go etc.). At the same time a "Hot" plug used in a highly modified engine that is driven hard consistently (racing) will simply retain too much of the extra combustion temperature and burn itself up (usually cracking the porcelain, and potentially doing major engine damage).


A spark plug that is too "Cold" for the engine/application will start harder, foul much easier, and generally be a pain to work with.

 

Why the coldest trailing plug you can get from dealer or auto parts store is a 9. you can get 9s made for a first gen all day long. any advantage from the diffrent design besides the 2 gens being platinum?

 

I posted earlier that Advance auto parts has a two year warrenty on their plugs, www.advanceautoparts.com
ifyou have one in your area, never worry about a fouled plug again.

 

Thanks. So how often would I have to change them to avoid one cracking and causing engine damage?

 

Oh yeah, and I guess I should get the cold type? In the manual, it recommends using:

NGK BR7EQ14 for Hot Type
NGK BR8EQ14 for Standard
NGK BR9EQ14 for Cold Type

When I bought the first set from Napa, they sold me the Cold type. Now I need to get a new set. I'm going to be doing a lot of highway driving on hot days, so what do you think?

 

Also, there's probably going to be stop and go traffic, so would the hot plug keep the heat down?

 

Standard 2nd gen plugs are not platinum. The platinum plugs (NGK BURxEQP-14) were standard on 3rd gens and, I believe, also the 2nd gen Turbo II.

Persoanlly I tend to find the 2nd gen plugs last longer than the stock 1st gens.
I use a standard 2nd gen setup of 2 9's on trailing and 2 7's on leading...

 

ok, dragging a thread from the dead, sorry, but it's a good one...

Ok, I want to get some new plugs for my -SE which sees mostly spirited driving and autocross, but some street use as well. Sounds like I want a colder plug, but do I want to do like an 8/9 split lead/trail or what? Suggestions?

Going w/ jacobs wires as well if it makes a difference.

 

i would also like to know who is running 3rd gen plugs and what the number on those would be.

 

As I said before:
NGK BURxEQP-14

Where x is the temperature rating of the plug.

 

I would suggest 9's all around if the car will mostly be driven hard.

My car unfortunatly sees too much city driving, hence the 7/9 split...

 

why 3rd gen trailing plugs, is it because there 9 vs the leading. I am thinking of doing this change.

 

I'm not running 3rd gen plugs. I run 2nd gen plugs. 3rd gens and 2nd gen turbos use platinum plugs.

I run a 7 in the leading because in the stop and go/low speed trafic I'm forced to endure a colder plug would allow carbon to build up on the plugs. The trailing plugs supposedly get a lot more heat than the leading so the colder 9's I run there keep those plugs from getting eaten up.

It's actually a stock 2nd gen plug setup from my local Mazda dealership.

 

I've been experimenting with different plugs lately and have to agree on using the 2nd or 3rd gen plugs. The only difference is I run the trailing plugs (9's) all around. 7's would be way too hot on my street-port with around 25* on the leading ignition timing.

 

No kidding Revhead...

I'm planning on getting 3rd gen plugs next time I replace mine.