I've been using synthetic lubes in all my vehicles for quite some time.
They last longer with fewer repairs, get better fuel mileage especially in winter and are easier to start on cold mornings.
I bought a 1993 Ford Ranger, new, changed to synthetics in the engine, and transmission within the first 1000 miles. The differential later. I change oil in the engine at about 9 to 10k and even at 197k never need to add inbetween changes. I've never needed any internal engine, transmission or differential repairs.
Even though I don't drive it much any more, I still intend to keep using synthetics in it if only because it starts better in winter if/when I need to use it..
Unfortunately the body has deteriorated greatly since the hail storm last spring April. Hundreds of dents with paint starting to show signs of cracking.
But it's only a truck to push, pull or haul with so it's cosmetics aren't important to me.
IMO...synthetics are a good investment.