Sorry to re-hash an old topic, but previous searches don't give me a definitive answer to the question. I have an '02 ranger xlt 3.0 v6 ffv. I'm seeing the Motorcraft AGSF12PP and AGSF22PP as the accepted plugs for my application. Is this correct? Thanks in advance.

 

Difference is the Heat Range, 1 is heat range of first plug, 2 is heat range of second plug, thats the only difference

Motorcraft Spark Plug part number decoder here: MotorCraft Spark Plug Information - Jim's Site

1-3 are colder plugs than 4-7

What that means, a colder plug has a shorter insulator so dissipates heat faster, but you want the tip to stay above 500degF and below 800degF, so too cold a spark plug can foul in some engines, and too hot a plug will cause pre-ignition.

The 3.0l Vulcan engine is a "pingy" engine, tends to ping/knock on regular 87 octane fuel, so Ford specs colder spark plugs, 1 to 3, there is an AGSF32PP that was also spec'ed for this engine

So if you notice pinging then go with the 1, if not then split the difference and go with 2
If you notice carbon build up on old spark plug tip then go with 3 or even 4

Spark plugs are DRIVERS CHOICE, Ford simply gives you a "starting point" for heat range AND best GAP, up to you to know your engine and driving habits
If you do alot of hauling you want a larger gap, lower RPM torque
If you are doing mostly highway miles, i.e. higher speeds then go with a narrower gap
+/- 0.005 is OK, even a change of +/- 0.010 is OK for specific use

 

Good info. Thank you, sir.