Vehicle maintenance

Gearbox
Grinding sound means gears are out of alignment.

Engine
Nothing, no smoke must come out of exhaust. Any smoke means that the rings aren't scraping oil off from the piston chamber. Start the engine and pull out the oil indicator, place tissue paper over dipstick tube. If any oil or gas comes out then the rings are worn down. The problem will get progressively worse. Finally do a compression test(video), http://www.dummies.com/home-garden/car-repair/fuel-system/how-to-check-an-engines-cylinder-compression/
 * Test the oil from sump that it isn't SAE90 gear oil when purchasing a used vehicle.
 * Certain brands of Isuzu bakkies use SAE30, while all other pickups use SAE90

Radiator
Replace electric fan motor every 50,000km

Engine additives
Only SAE40 oil has been approved by the mechanical engineering society ASME, nothing else must be used. http://www.ripoffreport.com/reports/auto-parts-prolong-super-lubric-prolong-engine-killer-1581.
 * http://prolong.com/about_tech "...This process is so stable that it is responsible for achieving the highest possible “1a” rating in independent laboratory testing designed to determine the anti-corrosive characteristics of lubricants...." Which lab of the https://www.asme.org/ tested it?