Date: Thu, 15 May 2003 11:00:01 GMT From: "Fred W." <nopsamt.ie> wrote in message news:ATIwa.13382$pK2.18344nopsam.indigo.ie... > This is really serious > I replaced the plugs in my 9000CS with those bosch four pronged thingies in > January. The engine seems the same but fuel consumption has increased from > 30mpg to 23mpg . > Are these two factors related? Yes. Get the correct NGK plugs. Nothing else. The engine management system uses the plugs as sensors in the combustion chanber. > Also ,if NGK plugs are the way to go why does the haynes manual recommend > Champion RC9YCC4 plugs. Mainly because the Haynes manuals suck. I wouldn't use champion plugs in anything more sophisticated than a lawnmower. > Should I change the plugs ? Obviously, yes. ;-)