Re: 02 ford ranger edge
NOTHING beats regular fluid changes. If you don't plan on towing a small trailer or camper regularly, or hauling a lot of tools in the bed on a regular basis then adding a cooler would be a waste of money. Some might argue that it's good anyway, but in cooler climates, the cooler can cause fluid temps to drop taking twice as long to get up to proper operating temp. I wouldn't add it if it's not necessary.
Be sure to change the axle fluid, transfer case fluid (if 4x4), engine oil, transmission oil and filter every 30-40K, and get the brake fluid and power steering fluid flushed every 40-45K. Coolant can be changed when necessary, you can get test strips that give you the freeze point and pH level. For best performance, use synthetic oils.
'11 Ram Quad Cab 4x4 SXT 5.7L HEMI (stock); 48,500m
'06 Pontiac G6 GT 3.5L 220hp; 64,000m
'12 Chrysler 200 Limited 3.6L 283hp; 28,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!