I've read quite a few threads on the NGK Iridium plug as a good choice for the XJ8. Is there a reason the Bosch Iridium does not get much airtime?

Has anyone noticed a performance difference in the two?

Just curious - any feedback is appreciated.

I am looking to change my plugs. I pulled a plug from each bank and they are Autolite Platinums - 3924. Plugs looked good, but are worn. The car runs very smooth and I actually wonder if it could possibly run any smoother. I would hate to spend $7.00 per plug for no reason!

 

I used Bosch in 4 of my jags 93 XJ-S 4.0, 95 XJ6 4.0, 99 XK8 4.0 & 00 S-Type 3.0 over the past several years with no problems to date. It is all in what you want.

 

Read the lower posts here, for me NGK.

https://www.jaguarforums.com/forum/x...roblems-62830/

 

This being said I ask myself what plugs were installed that failed and were they matched for the car application, RE hot or cold plug, gap setting. And the one other important note is what was the gap of the plug when it was installed? A change from years past you can get a plug with 1, 2 or 4 grounding contacts for the probe to fire.

Spark plug - Wikipedia, the free encyclopedia
Spark plugs FAQ

When I pull a plug and it is fouled I look for a reason. If I had one plug fouled I would be looking at the plug but if you have several in the same car I would be looking at the fuel used, fuel presentation and the type (hot/cold) plug along with the proper gap and the clean and good connection with the coil pack.
The plugs are your choice.

Do your homework to be sure you are installing the proper plug for your car.

 

Hi
Last March we had our 100,000 miles maintenance on our 2001 XJ8. I purchased 8 NGK Iridum BXR6EIX-11 thru Advance Auto Parts online (part# 3764) for net total of $36 (that is $4.50 per spark plug).

I ordered & paid for the plugs online with promo code A123 ($20 off of $50 order - 40% savings) and picked them up at our local Advance Auto store. These plugs are designed for the XJR. Here is the weblink to these plugs: Buy NGK Iridium Ix Spark Plug 3764 at Advance Auto Parts

I sent this email to NGK:
Our 2001 Jaguar XJ8 is Naturally Aspirated GAS Engine - It is not the supercharged version.

I noticed on the NGK UK website that the upgrade iridum spark plug for our engine is listed as BXR5EIX-11 (which is not even listed on the NGK USA website).

I also found the spark plug Part Number breakdown table in this PDF on NGK UK website. Looks like the NGK BXR6EIX-11 is almost the same spark plug as the BXR5EIX-11. Just 1 more higher in heating rating number (means it is just a little colder spark plug).

Can I use NGK BXR6EIX-11 spark plugs in our 2001 XJ8 without any problems? It appears to be for XJR models. I could not find any NGK Iridum plugs listed for XJ8.

Here is their email reply:
The 1 step colder heat range won't hinder performance.

Our results:
We had our mechanic put in the NGK BXR6EIX-11 8 months ago and we have not noticed any difference in fuel consumption or performance.

Jim Lombardi

 

I use Bosch Super 4's in my XJ8 and they are really good plugs. I wouldn't use NGK plugs in any of my cars, I use Champion plugs in my Herald but will change them to these plugs when I get the chance.


Bosch Automotive Aftermarket - Spark plugs - Bosch Super 4

 

Hi
Here are extracts from the sparkplug chart on the NGK UK website.

Note - the information for XJR model 97-03 4.0 Year 03/00 -> 03/02
is on 1st chart as -Stock# 5464 Part# BKR5EIX-11
also XJR model 97-03 4.0 Year 09/97 -> 02/00
is on the 2nd chart as - Stock# 3764 Part# BKR6EIX

Looks like both of these spark plugs can be used on certain XJR model years.





Here is the weblink to NGK UK sparkplug buying guide:
NGK Partfinder Buyers Guide

Jim Lombardi

 

Nor would you- spark plugs have no influence on fuel consumption or performance. Their only job is to light the fire which they either do or don't do, as an all or nothing job. This assumes that the plug is of the correct heat range.

Marketing of spark plugs is much like the soft drink or mega brew beer industry- 99% smoke and mirrors advertising, 1% product.

 

I believe this to be incorrect. Reading the NGK web site for example it is quite clear that plugs of incorrect spec., incorrect gap or worn/damaged will affect the car's performance and common sense says if the spark is not timed right or strong enough, ignition of fuel will not be optimised and so power will not be optimised.

Clearly it is not an all or nothing job. And a very cynical reply.

 

I'm on Bosch iridium's with no issues and running beautifully.

 

Same here, changed at 80K miles, got rid of a small 'fluff' at tickover and mpg went up by 2-3

 

There are no NGK plugs available for the S Type 3.0. So I went with the Bosch Iridium Fusions. Those are the plugs with 4 electrodes. I didn't fall for any marketing hype. I bought them because replacing the plugs is a B#$%h! I figure with 4 electrodes to go south, they should last longer than a single electrode plug.

 

Except that most stories involving electrodes that broke off into the cylinder seem to involve Bosch plugs.

 

Strongly disagree with such a simplistic and pat answer.

You forgot two basics .. gap and freshness.

In addition there is suitability of the particular design for the intended application. For example extended versus shrouded tips, resistor versus non-resistor, electrode design, and electrode material.

Finally, a plug can fire but have poor flame front propagation because it is the wrong design for an application.

There are a lot of hyperbole in the marketing of sparkplugs, but there are also real world differences. The trick is to know enough to figure out the right ones in the circumstances at hand.

If one is not up to the job, then the current factory specified replacement is a good choice in a stock engine.

 

D'oh!
Now I just quartered the odds.
I'm F'ed!

 

Not sure that this issue in not one of those that happened to one and spread like wildfire suggesting it pertains to all or many. I would not get overly concerned. Bosch has had a good and long standing reputation that is also recognized by many racing teams.

 

have we come to a verdict on this thread, on which is better or preferable? or is the answer just worry about the gap?

 

You will not see a verdict on the plugs because we have a diverse group of people that are strong in their opinions. I personally use Bosch and others use NGK plugs, am I more right than them? NO! It is just my preference. I researched and researched to the point that I was just wasting my time to find out what plug is better than another and the answer is there is no answer but others will say differently. They are all good and get better as you move up in the scale of that manufacture you choose.

 

good answer, so verdict is, get whatever you like, but get the right gap

 

So what IS the right gap on Bosch plugs?