Bosch (4041) HR9DPY Platinum Plus Spark Plug, Pack of 1

Bosch platinum plugs (reg, +2, +4) have worked very well for me in newer cars, not so well in those older than about 1999. They like higher voltage ignition systems. They can misfire with lower voltage. Sometimes larger plug wires fix it, it depends on the overall design of the ignition system.

Despite the hype on the web and anecdotal stories, virtually all spark plug manufacturers recommend against using anti-seize compound when installing plugs. They nickle-plate the threads to protect against seizing. The anti-seize compounds, even copper based, tend to increase the resistance to ground, and to upset the torque required to seat the plugs. The silver based compound will seriously increase resistance causing misfires and serious overheating of the plugs, and I have experienced the plug ceramic tips breaking off and falling into the cylinder. It sounds like a bad valve lifter and can damage the cylinder or valves. Copper based compound is less resistance, but still often...Read more

I have used the Busch Platinum Plus spark plugs in 2 different vehicles, each with the FORD 4.6-litre V-8 engine (the same #4041 plug is also used in Cadillacs, Chevrolets, and other GM cars and trucks)-- and I have accumulated about 150,000 total miles on cars equipped with this plug, with all cylinders firing evenly and giving excellent fuel economy.

I change the spark plugs at 30,000 mile intervals -- being very careful to BE SURE that all the spark plugs are gapped properly at .054".
When installing your new spark plugs, always BE SURE to apply an Anti-Seize compound to all the threads.

Also, BE SURE that the Bosch Platinum-Plus spark plugs are properly torqued to 180 inch-pounds (15 ft.-lbs.). Too loose, and the plugs can back out -- too tight, and the threads in the aluminum cylinder head may strip out !!

A 1-foot length of 3/8" fuel hose can be slipped over the end of the spark plug so that the plugs can be easily threaded in...Read more

The plug performed as expected, no noticeable change in mileage. I might be tempted to try a different plug next time.