I am trying to determine how old the plugs are in the 91 xjs I just purchased. I have the history of the car which shows mileage.

Does anyone know when the BR7ES spark plugs came out?

The plugs look brand new without a spec of dirt. I am fairly certain they are but I want to go by a worse case scenario. The year these plugs came out and the mileage driven on the car since that year. Though, I do not want to do unecessary work. There is enough to be done already with the cooling system.

I think I would be at a max of 10k as the car has been driven about 1k a year for the past decade, but I want to make sure. Something is telling me the 7ES came out around 2009?

 

Hi

2nd June 2009

 

thanks! that means no more than 3000 miles have been put on these plugs. Most likely less than 800. saves me a lot of work. since we are on the topic. what is the recommended change interval for the BR7ES?

 

I have an NGK Australia Catalogue in the library, and BR7ES is listed for the Marelli HE engine. That Catalogue is dated "1998-1999".

Not sure on change times, and it would depend on many things, including fuel used, distance travelled EVERY time that engine is started, etc.

The less mileage, shorter plug life.

I run BPR6EF in ALL the HE engines I care for, and 40000kms in the "normal" change time down here.

 

That link appears to be for BR9ES not 7.

 

Spark plug specification changed to "hotter plug" to allow deposits to burn off during normal driving

See this TSB (technical service bulletin)

12-55 Spark Plugs ? Revised Specification V12.pdf

 

Keep in mind that NGK plugs are hotter as the numbers go down, not up.

BR6 is hotter than BR7, and so on...

 

I don't know off hand what Jaguar suggested but I'd say they should easily last 30k miles if the engine is running well and isn't excessively worn.

They'd probably still be working quite well even at higher mileage that that...but if you have a Marelli car you might start getting nervous about how far the gap has opened.

Cheers
DD

 

I bought a 94 with 78,000 miles on it and the plugs were clearly original, never changed. I think the gap had opened up to about 0.045", but the car ran fine.

 

I had a 92 Series III V12 sedan and in the owners manual it said to use the BR7ES, so they have been around for a long time.

 

ok, that negates my strategy then. they are shiny and new looking. I think I am being overly paranoid. I will replace them in another 10k miles.

 

I agree with Doug on this one, if the gap is too wide the high compression Marelli (mine is listed at 11.5) will blow out the spark and not burn effectively.

 

I don't know when those specific plugs came out but did recently change my plugs and wires. The car had Autolite plugs installed, obviously quite old. None of the old plugs were badly fouled but all the gaps were from .050 -.055. I changed them because the car was running a bit rough, and a I went through the project also found that a couple plug wires appeared to have been chewed by mice (YIKES!). Even so changing the plugs and wires didn't noticeably improve how it was running. I'm glad I did it though since I've read many times that spark problems can lead to those Marrelli ignition problems, a bit more peace of mind for me now.