Good Afternoon All,

This is my first post after visiting several times to look for answers.

My situation is this: I am changing the plugs on my 2003 S40 for the first time. (Thanks to other posts, I was able to locate them and know that I needed a T-30 socket to remove the cover!) However, when I removed the original plugs, I noted a 5 digit designation on them: R6 291. The replacement plugs from the dealer had R6 781. The dealer says they don't have a clue as to what the number means and Volvo USA refers me back to the dealer, but the dealer swears that they gave me the right replacement plug. The plugs look the same except for a minor difference on the connector on the top of the plug and both are made in Germany (Bosch?). Does anyone know if this is the plug's part number? Engine is the B4204T4.

Also, I don't see anything on the life of the spark plug wires. I hope they last longer than the ones used with the old distributors as these things are not cheap!

I am sure they are the right ones, especially if you bought them from the dealer. The R6 is probably the part number, the other numbers are probably just production numbers. My personal opinion is that Volvo plugs suck bad! I wouldn't waste my money on them. If you search you will see many people end up replacing them every 12,000 miles or so. My owners manual says to use Champion plugs which are the cheapest plugs made. I used Autolite Double Platinum and they are holding up very well.

Interesting. The independent garage mechanic who I have do work on my '89 740 stated that Volvo does not make their own plugs, but rather it is done by Bosch. He normally recommends staying away from dealer plugs except for Volvo which are made by Bosch. His recommendation was Bosch or dealer plugs, but that the parts places have usually given out the wrong plug for S40's 2003 engine so go to the dealer. The other plug he has used has been the Autolite double platinum. He did say to stay away from the Champions in the Volvo.

NEVER NEVER USE BOSCH PLATINUM!!!!

I had bosch platinums in my Chevy S-10 Truck and a piece of the electrode broke off and cracked my valve.

I found this is not an uncommon problem after doing some searching.

I used the Autolite Double Platinum and they run perfect.