Mercedes Spark Plug Kit - Bosch 0041598103

I was worried by review MB Driver on Tue, Jun 18 at 09:17AM but I can't say if this is true or not.

I am new to the European car community as I bought a 2012 CLS 550 in March and then bought a 2015 CLS AMG 63S three weeks ago. Knowing little about where to purchase parts, a friend referred me to your company. I have run into a problem that your staff can’t seem to get right, and I have honestly lost confidence in using FPC Euro in the future. According to your website, P/N KIT-ISKM278 is the Bosch version of the OEM spark plug for both cars. I was led to believe that these we the direct replacement for the OE part. They did arrive in a timely manner, and I got to work installing them on both cars. I finished with the AMG and got about ½ way through the installation on the CLS 550 went I had an official service bulletin from Mercedes forwarded to me coving the replacement of spark plugs on these to cars (M157 and M278) I have attached the bulletin. Link: https://techtips.alleuro.com/wp-content/uploads/2020/02/mercedes-spark-plug-index.pdf According to the bulletin, the spark plugs must be indexed properly to avoid engine damage. The non OEM Bosch plugs will not index properly, they end up 180 degrees off. On closer inspection, the threads from OE to non OE, start at a different point….180 degrees different. I also checked the stock plug index in the car and found that they index well within the requirement from the Mercedes bulletin. I also see that there was a review on this very issue on your website. On Monday I contacted FCP and spoke to John, a sales REP and shared my concerns and sent pics of everything and included the bulletin. He arranged to give me a partial credit for the already installed non OE Bosch plugs, and agreed to ship a set of OEM Mercedes spark plugs to me overnight as a courtesy as I initially requested to pay for 2nd day air. All seemed well, until I checked tracking on Tuesday, only to found they were shipped regular ground…I needed the plugs TODAY to finish my TWO cars that are inoperable. Tuesday I reached out to FCP, and spoke with Nick as John wasn’t available. He assured me he would handle getting another set of OEM plugs out to me again OVERNIGHT to arrive today. Checking tracking, the shipping label was created this morning…… All I want is a full refund for ALL of the plugs so I can source them locally TODAY, and I can’t even get a commitment for that….

While these are listed by FCP as compatible with the M278 and M157 engines, they are not. Not only was the gap set significantly larger than what was on the factory plugs with 70K on them, but more importantly there's no way to index them using the recommended torque setting. These engines require that the plugs be indexed so that the ground strap is facing away from the injectors. At first I thought this was urban legend, but when I carefully removed the factory plugs they were all indexed correctly. If you have a Mercedes with either of these engines do yourself a favor and learn from my mistake, get either the OEM MB plugs or get the correct NGKs.

M157 sparks hard to index but they're all line up how i wanted them to be. Currently stage 1 for a month and driving the car hard, so far no issues.