Hello All,
I was wondering which spark plugs to get for my 1999 Infiniti Q45. I read on several posts that the ones to get are the NGK PLFR5A-11, I ordered these plugs (NGK PLFR5A-11) as I know Bosch is a huge "No No". Now I am reading NGK-PLFR5G-11, NGK-PFR5G-11, NGK-BKR5EIX-11, NGK-7090. It is really confusing, When I look online I see the NGK PLFR5A-11, NGK-PFR5G-11, and NGK-7090. Some sites say the ones I ordered NGK PLFR5A-11 will not fit.

Can someone please help as when I do a search for spark plugs in the forum...the bulk of posts I see say "8 new spark plugs".

Thanks everyone...

What I am wondering is after further research I see the below...

I bought these...(Fits: Infiniti Q45) = NGK Part # 6240 / PLFR5A11

Do I really need these...(Fits: Infiniti Q45) = NGK Part # 2647 / PFR5G11

And what I have seen researching is that they should have a .045 gap

mac,if confusing like that , and you had no problems from what's in the car (factory plug I assume ?). Uncrew one of those oldies but goodies and get THAT plug - probably will be NGK #- write it down . Simple & best now IF that EXACT # still currently available.Any other "Cross-referencing" , or if a SINGLE slight DIFFERENCE in part # offered - you gotta CLOSELY compare them to that old plug as far as thread depth,total extension (ground)beyond threads, how far the "Nose" (porcelain+Ctr. electrode) "projects", gap of course ; you hold up SIDE by SIDE This just IF 'n you believe in the old "Not broke Don't fix it" philosophy ?
p.s. I believe the 5 in the # is the "Heat range" figure.ALL other "digits" are physical parameters,and IX =Irridium,P= probably Platinum,Don't know the B's .

Thanks Macgiver, the car was given to me y my late father. He used Bosch Plats in his truck's and car's before this one. I know he did a plug job, and presume he used Bosch in it. It seems to have a miss so I decided to see if changing plugs from Bosch to NGK would help. Since I am unable to do the work, due to an accident, I figured I would ask to see if someone knew if the PLFR5A's would be ok. I found them for a good price, and didn't wish to pay markup on the plugs. I didn't wish to use Bosch plugs again as most posts say not to. FYI...5 should be the heat range, I believe the lower the number the hotter the plug.

Thank you for your input.

Might you have your owner's manual? I think most Nissans of the era called for the middle ground NGK PLFR5A-11, but I will try to fnd the manual online to compare.

mac, gothcha so your open to change - here's what I did in a VG30DE -eng. supposedly VERY sensitive to Alt.plug replacements . I installed NGK IX type ONE COLDER (AZ gets 119'deg.+) - that allows me to go an extra couple degrees Adv. timing(even in that heat) , much better response, noticeably better power - basically Irridium is noted "under stressfull heat conditions " to cause reduce Knock potential , thus reducing/lowering the "Retard Band parameter" , basically ECM' Ign. mgmt. is NOT RETARDING AS much / AS often - to a significant enough degree as to be VERY NOTICEABLE Biggest rewards , again - under harshest street running/ high - AMB. & Eng. temps!! You may come across many valid sounding discussions that NO plug (alone -NO SH%$&@TT) ever will get you ANY noticeable difference in performance - what's left out of that theory/discussion is Some plugs ,like Irridiun, can ALLOW - SYMBIOTICALLY OTHER Adj. , & parameters to achieve a MORE POWERFUL POTENTIAL usually through further - radical adjustment or "MODS" etc.,etc. = END RESULT ,yes NOTICEABLY better performance!!
ONE PARTICULAR unique plug design CAN far surpass the achievements of what various other plug choices may yield. END of discussion TUNING

I found some snippets of the FSM for my 2001 and it called for these:
PFR5G-11 standard type
PFR4G-11 hot type
PFR6G-11 cold type
Gap 1.1 mm (0.043 in)

Unfortunately, I can't easily locate the owner's manual for 99, for 100% certainty. I will assume the same engine takes the same plug, unless someone can look in the appropriate manual and tell us for sure.

The plugs you bought will not work. According to NGKs web site, they have a reach of 1.25" vs. the correct reach of .75" Worst case, your plug will hit the piston heads... best case it just runs poorly due to the spark being at the wrong place in the combustion chamber. I suspect you'd have a worst case scenario on your hands, since it's an interference engine. Two teeth off on the timing chain can cause catastrophic damage.

EdBwoy wrote: ↑

Thu Apr 19, 2018 10:20 pm

PFR5G-11 standard type
PFR4G-11 hot type
PFR6G-11 cold type
Gap 1.1 mm (0.043 in)

That's the recommended plug in the 1999 owner's manual as well. https://www.infiniti-techinfo.com/refgh ... ti-Q45.pdf

I would just go with the normal range plug as specified, unless you have a specific issue you're chasing to push you toward a hot or cold range plug. We have too many stories over the years of non-specified plugs not performing well to take a chance on something else.

You should just call the guys are Scotsdale Iniiniti (everythinginfiniti.com) and just order from them. Then you get the right part and their prices are good.

Standard plug is PFR5G-11. FSM says not to gap them.

mac,absolutey don't need to ADJUST the gap , but ain't a bad idea to measure/ check'm, at least hold them up to the light to see that no Jerry Lewis assembling the little cardboard "toilet-paper" roll onto the end DIDN"T DROP'em on the damn floor! Leaving ground electrode BENT.