Spark plug Bosch 4457 as replacement for NGK BR7EF

In respect to the V12 5.3L engine, has any person had experience using the Bosch 4459 Platinum +4 spark plug, 5’8" hex, beveled (tapered) seat, 14mm thread, .708" (17.98mm) reach, resistor, heat range 9, as a replacement for the NGK BR7EF standard gap type plug, 5/8" hex, beveled (tapered) seat, 14mm thread, .709" (18.01mm) reach, resistor, heat range 5 - Bosch heat range numbers are reverse to NGK heat range numbers so they are close in that respect -I have used the Bosch Platinum +4 in my 4.6L 8 cylinder, coil-over, 2005 Lincoln Aviator with good results - here are two pictures showing the spark end - thanks,Tex.

no direct experience here, but I’ve been suggested not to swap single electrode plugs to 4 electrodes plugs, as those can be less efficient as they “hide” the spark for a part of the chamber

1 Like

Will keep that in mind - have not purchased spark plugs yet, but do have to put new spark plugs in so that is why I reached out for information - Tex.

I have never read anything that would indicate that multiple electrodes plugs are less efficient than single electrodes, especially in a naturally aspirated engine.

I think they work just fine: allow me to amend that… Multiple electrode spark plugs will not give you more power or last longer as many advertised. They’re just a spark plug (unless it’s a rotary engine).

Just don’t forget to use anti-seize on the threads!

1 Like

I respectfully disagree with the above. Firstly- with a complex combustion chamber, and set up for max power- not being able to clock is , in general, a clear disadvantage. That said, I tested and run the Bosh 4’s in my 1 ton Dodge Ram V 10. Bought truck new and ran #'s. Really gave better MPG. Best at mixed highway- up from Solid 12 to nearly 14 MPG. 4 inch bore, Slow revving. The plugs have merit to me but not going to run in my XJS. “Idiot” plugs for all weather running a true slow-revere. More electrodes has to mask more. My guess is that that would be a potential bug-o-boo in a HE.

1 Like

I’m going on data I acquired on a dyno: no plug showed anywhere near that kind of improvement.

I also racked up about 1000 miles of on-road testing, same result.

As Jerry would say…YMMV.



If you have dyno data for (or against) multiple electrode plugs- great. I do not. My (now older) Ram really likes them- I was so surprised I shared same! Gain solid 1 MPG real world is Hudge, right?Tried against stock (Champ?) and Auto lights- recommended heat range. Anyway- what about the high RPM .025" gap thing? Guess Bosh design is equivalent of much bigger gap. My gut said- what is good for a “self cleaning” , high efficiency “idiot” plug may not be ideal for a “power by May” high RPM “hobby” car. Even problematic . On the Dyno did you Index gap to exh . vlv.?

1 Like

Post Script: YmmV = ??

Yes, I did: I saw no measurable increase or decrease in the performance on the test mule.

I did index the plugs on my race Datsun engine, but that was just because of the extremely high compression ratio that it ran. I did it so that the ground electrodes wouldn’t hit the top of the piston!

1 Like

Interesting. Apples to oranges- , but lots of American, wedge, push rod and 4" + bore engines do seam to like index plugs and “gap by timeslip” tests, based on published vintage data + slips. Glad I didn’t bet on your Jag. test mule as I’d have surly guessed Bosh 4 “open at top” (bottom) stye vs. conv.- open at side style would Have to make very measurable difference on the dyno! Test mule was May, not flat, correct? Trivia “for the record” Ram v-10. 4.11 geared. Road test with all starts in 2nd (5 speed stick) and 2 wd. only. T stat 180 vs. 195. Mid grade “89” fuel. Never more than 2000 lbs in bed (load miles small fraction of any recorded anyway) and 6100 scale weight wet- no driver. Shifting tended to be well under 3600 rpm.

1 Like

There are many different results for many different combustion chamber shapes: my test mule was a Datsun 1200.

1 Like

Ok, cool. 1 man, 1 vote: I’m with Mr. 12 Coupe above, for his reason and the gap thing- I’m not willing to test on my car, so I vote no- but if somebody tries them in a HE- please advise. Best luck all.

1 Like

Your Mileage May Vary, a favorite saying of the late, great, @mouton!


I am reposting an excerpt from an old thread on these plugs:

Anthony Ching wrote:

I am planning to upgrade my 89’ XJ-S V12 with Lucus Ignition by replacing
with Magnecor wire and Bosch Platinum 4+ Spark Plugs. Could anyone
advise me what is the proper
Bosch Platinum 4+ Plug model number and proper gapping for my English model?
Where can I buy the spark plug through mail order?

Dear Anthony and List:

I am no master mechanic, like many others on this list, but I have
learned one thing in life, and that is that you never are
sorry for going first class:

“On November 2, 1999, Popular
Mechanics chose the Bosch
Platinum+4 spark plug as the
winner of its coveted 2000
Design & Engineering Award.”

If all of you are like me, nothing is too
good for our cars. Intuitively, this seems
like a good product, and is recognized as
such by industry and racing successes (I don’t
work for these guys…usual disclaimers apply).

I am extremely pleased with these plugs, although
it is hard to determine if the smoother idle and
better performance is a result of:
a) New MARELLI Rotor and Cap
b) New Platinum +4
c) Magnecor wires
d) AJ6 Torque Plus Intakes
e) all of the above

If budget is not a concern, it can’t hurt and can only help.

The plugs are NOT ADJUSTABLE nor need they be.
Strange as it sounds, they are designed that way from the
factory. I read this on another automotive web site I
posted to the list last week (can’t remember the URL).

The part number is 4457, and you can get them at major auto
stores in the USA [ don’t know about HK :frowning: ] On behalf
of our little band or rabid Jaguar XJ-S owners, I queried
the web site and it looks like
1987 is the first model year for the XJ-S that they specify the
application for this plug. For the older cars, they specify application
of their “Platinum” plug, model 6231, but only from 1981-1986.

Results vary from 1980 backwards for all Jaguar V12 engines.
Happy early Xmas shopping for your kitties…

“World Peace Through British Cars”

Wayne Estrada
Richmond, VA USA
1989 XJ-S Convertible (Dorchester Grey)
1989 Vanden Plas (Alpine Green)
Please see my cars at:

The notable bit is the part number in this thread is 4457, and NOT 4459 like the recent poster is asking about.

At that time, the 4457 part came directly from Bosch. I had bought a set of these way back when, but had not put them in. Lots of life intervened.

But I DO intend to put these in, probably this spring- will do a good shot or two of Sea Foam and some Italian-tuneup style runs (I have a 5 speed in this car) and then change the oil and the plugs. I am looking for a smoother idle and somewhat better performance throughout the RPM range. We shall see.


1 Like

E) is the most likely answer, since with that many changes, it’s nearly impossible to determine which made a difference.


Yeah, my experience, too.

Add to it: fresh tank of the freshest, highest octane fuel you can find.

It is the sum of all of the little things that contribute to making the V12 sing most sweetly, and fuel quality is right in there.

1 Like

At the risk of starting another octane war… these engines don’t really require really high octane: here in Colorado, 93RON is more than enough for any pre-1990 Jaguar.

Unless an engine experiences detonation, the use of higher octane fuel does not translate to higher horsepower numbers.

1 Like

Me neither: re: octane wars. More power only comes from more fuel plus more air, otherwise, performance can come from a lessening of weight and/or drag. In the bigger picture, that’s about it.

I am talking about smoothness of running, and a sense of wanting to run harder and harder, longer and longer, the engine urging for more, more, more. That engine (with freshest, good quality fuel) just wants to run and is at its happiest running hard and fast.

That is the difference fresh, good quality fuel makes in my car, all other things being equal. Night and day.


1 Like

Hello Mike90 - I found these specs for the Bosch 4457 and Bosch 4459:
4457 is heat range 7 and 4459 is heat range 9
4457 reach is 17.5mm and 4459 reach is 19mm
both are tapered seat, 6000 resistance, 14m thread
Bosch heat range is Cold-

NGK BR7EF is heat range 7, reach 17.98mm,
tapered seat, 5000 resistance, 14mm thread
NGK heat range is Cold - 10,9,8,7,6,5,4-Hot

Bosch 9 is NGK 4 - Bosch 6/7 is NGK 6 - Bosch 5 is

Any insite as to the effect on my 1991 V12 if use Bosch Platinum + 4 is what I am trying to find out - with you mentioning the Bosch 4457, instead of the Bosch 4459, I see that it is a spark plug closer in specification, as to the reach and heat range to the NGK BR7EF - so now I ask what you, and all the other posters may think - thanks, Tex.

Fun fact- Rock auto lists the gap at 1.6mm for 57. That is .o63". Assume 59 similar. That is a big concern to me , at least over 3000Rpm. Big gap+ 4 paths PROBALLY big advantage these plugs have in modern American cars. My slow-rev. Ram loves them. Your fight- if they work, great for you and me. My V-8 Fords with little 4.6L V-8’s like them, but, unlike Ram- good idle-little fuel economy gain. Think Modular Fords about .o54" spec gap. Good luck-please advise when you try them. I’ll hold off. Do imagine they would yield sexy idle. Post Script- rock auto has but 2. Obsolete or maybe just low stock- do not know.

1 Like