Once had a Jeep with a 4.0L come into my bay. 93,000 miles for its first oil change.
Hyundai and Kia GM 5.3, Toyota 3.0, and some Ford engines all coke and gum up like that from too small of oil galleries. Hyundai and Kia are the worst.
I bought a '93 Dakota from a dealer years ago. It was called a "Certified" used auto, with a 3 month/3000 mile 3rd party warranty. In hindsight I should have checked it over better, but the relatively low mileage and warranty blind sided me. (85,000 miles... I bought it to replace my '91 with 198K miles)
The first thing that I did was bring it to my mechanic and had them flush the coolant and replace it with a "low-tox" green. That's when anti freeze started running out of it all over the place. I had a new radiator replaced under warranty; then the transmission started slipping. I took that back and they said there was nothing wrong with it and that it was normal for it to slip when going into third, but made some adjustments. We went back and forth on it but they refused to fix it so I called the number on the warranty certificate... and got a recorded message telling me to contact the dealer. In hindsight that's when I should have contacted a lawyer.
I finally figured out that the previous owner had never changed the oil. When he developed an antifreeze leak he filled it with stop leak and traded it. At the time I was self employed, working every day and driving 1000 miles per week. That truck was so bad that if I had to go very far from home I would call the garage and make sure they would be available if I needed a tow home.
Among other things I ended up losing the timing chain, which trashed the top end. I had it towed in, and it took two weeks for them to fix it. When they were almost done I lost the CV shaft in my Celebrity, so they towed that in and I took the truck. Driving back to the same town I had broken down in before I filled the truck with gas... and lost the fuel pump. I called them again, asked the owner to bring the wrecker home and grab the truck on the way past. I then hitchhiked the 50 miles home.
I lost a fuel pump just a mile from the garage; once again called them to come get it, then hitch hiked home. Just 3 months later I was out in the woods looking at a map when the engine died. I called and told them to get another one, then walked out of the woods and got a ride home. I changed it right there in the woods. The brand new factory transmission I had bought failed in about 4 months... actually I don't think it was any good right from the start. I was living by a lake and when the temps got cold at night would have to drive back and forth between two small hills until the tranny fluid would get up to temp enough to climb them.
I dumped enough money into that thing in the first year so that I could have bought a brand new 4x4 Ranger... not including the wrecker bills. I had to take out a loan to replace it, trading for a Toyota. In hindsight I should have kept running my '91 instead.