I always wanted to buy one of these for myself, because I always thought they looked so cute! Unfortunately, other concerns, needs prevented me from doing so.
It's a Chevy S10 that was spec'd with the reliable low power engine and a different body. It's not really anything special in terms of reliability. The post office simply committed to keeping them for 30yr then followed through. It helps that they were working with a purpose built commercial body and not an "engineered to a price point" stock truck body. Any other similar truck platform of the era would have fared similarly. The late 80s/early 90s were a time when the electronics of the 90s were coming to maturity but hadn't yet snowballed in sheer volume like they did in late 90s and early 2000s.
In any other context the internet would be all "hurr durr, GM builds junk, muh indestructible Hilux because top gear". Goes to show you how much reputation and framing matters.
In hindsight the best available platform of the late 90s/early 90s for sheer reliability (in postal use) would have been a 1st gen Explorer only because the front suspension is better suited to handling potholes and driving over curbs all day and the 31spl 8.8 rear axle is complete overkill for the application (all other differences are minor/negligible IMO).
> The late 80s/early 90s were a time when the electronics of the 90s were coming to maturity but hadn't yet snowballed in sheer volume like they did in late 90s and early 2000s.
A very valid point, the ECU's etc around 1990 got a lot of the benefit of having a modern ECU with a fraction of the complexity and a lot of them where bulletproof in design.
Fascinating read on the history of computers in cars.
https://en.wikipedia.org/wiki/Grumman_LLV