Black129

I have read much debate about the use of Platinum plugs for the SL500 R129. I did some experimenting and I believe that I have found an answer to the question. "Do Platinum Plugs really word?"

A little back ground on this test. I have a 97 SL500 with K&N air filters. I wanted to see if the Platinum plug would give you that add horse power that everyone claims that they will get. I had a 98 Jeep Grand Cherokee which I added about 75 Hp to which worked GREAT with the platinum plugs, but it also had a MSD(Multiple Spark Discharge) and a 65,000 Volt coil running through 10mm race wires. The plugs worked great and I did see an increase of fuel mileage. With this knowledge i figured that I would go ahead and put them in my SL.

Before I put the new plugs in I took notice of my gas mileage. Now I pay attention to how many miles i get per tank and it is pretty much the same on every tank. I am a spirited driver and I am never afraid to use the gas peddle. I have done multiple 300-400 mile journey on a highway driving 80-90mph, mix of highway and city, and just city so I know pretty much what the car gets.

I bought the Bosch Platinum 4 plugs and installed them and just went about my daily driving. About 2 months of testing I started to compare my notes. The Platinum plugs were JUNK!!!!!!! I can't really tell if i am loosing power because the car still gets up and goes but I did notice a pretty sharp drop in fuel mileage. When I started looking at the results i found that I lost about 60-75mpg in just highway driving. The city/highway or just city did drop also but it is hard to put an exact number on it. Plus I began to notice a slight shutter in the motor when I was sitting at stoplights. It wasn't like a car with a big cam but when sitting a full light cycle the car would do a little engine shutter once or twice.

To complete this test I purchased Bosch CU- core plugs from mercedes(factory recomended plugs) and installed them and once again back to the normal routine. And as expected the gas mileage returned to normal(pre platinum levels) and the slight motor shake disappeared.

With this being said I do not claim to be an expert on cars. I have done a lot of engine modification on Ford mustangs, Jeep Grand Cherokees and a Nissan Xterra. I feel that I am pretty car savvy and that I know what I am doing. This was just my experience with testing on my 97 SL500 and this is just a response to debates on which plugs should be installed in THIS car. I know that Mercedes does not recommend putting Platinum plus in Mercedes engines that were not designed to use Platinum plugs and after my test I fully agree. I just wanted to let people know from my experience which plugs you should use in your SL500(r129) with a 199 engine in it. I hope this may help anyone who is contemplating putting Platinum plugs in there SL.

ChrisB

I was not aware of Plutnum Pugs.

I have nothing much to add ... except I'm trying to corner the market in most current R129 postings! Ha Ha.

Yor post was in the way.