To be honest, I just assumed the Bosch plugs would be great. They guarantee the engine will be smoother or they will pay for the plugs. On the interstate run, the engine was smoother, but it could be because the plugs were original. I have the same plugs in my 960 Volvo (They were in it when I bought it) and now some miles later they appear perfect and the car runs great. (Is Bosch better in Volvo's?) By the way, I don't have my maintenance book, do you know what the plug gap should be? I want to see how bad my original plugs were, if they were at all. Thanks...
1995 MB E320 Wagon, 41k
1992 Land Rover Range Rover County, 186k
1996 Volvo 960 Wagon, 105k
1996 Ford "Exploder" Limited 2wd
1982 Volvo 240 GL Diesel, 157k (61k on new gas engine conv.)