Ford 2006 Ranger Owner's Manual page 258

Maintenance and Specifications
2
For spark plug replacement, see your authorized dealer. Refer to
scheduled maintenance information for the appropriate intervals for
changing the spark plugs.
Replace the spark plugs with ones that meet Ford material and
design specifications for your vehicle, such as Motorcraft or
equivalent replacement parts. The customer warranty may be
void for any damage to the engine if such spark plugs are not
used.
258
2007 Ranger (ran)
Owners Guide (post-2002-fmt)
USA (fus)