It really depends on the engine and what it is.
If you have history evidence of an engine and what kind of abuse they can take- then it helps to know.
for me an example is the LS6.0 large fleets ran them with zero oil change to 250,000 miles. Only added oil at 1.5 qt low marks and never a filter. it was a mean torture test and 3 dozen iirc came out with flying colors. The fleet I worked before at ran them with descent nkt the best oil& filter changes at 30,000 miles up to 300,000 before tear down. A bit of shellack build up in a few spots as you would expect but not bad at all. When we bought our 01 suburban (used with 28k on it) thats what I did. I sold it at 205, 000 but should have kept running it. The 4l80e never got a service until that 201, 000 mark and it wasn’t supposed to. The radiator cracked and we were about to go on vacation so I had a shop do it and the oil change done and the mechanic did the trans without asking me- he noticed atf wasn’t looking great and figured if I didn’t want to pay he would just eat it (trying to be nice guy for me not knowing my gameplan) otherwise for that truck I was going to run trans till she died with no money into it ever- my experience has been if not towing heavy often and NEVER changing fluid you hit 275,000-300,000 then a rebuild of average cost.
Of course that trip was into a mountain in California and the first time ever the trans warmed up to 235 iirc towing a 16’ camper where I met BigT the first time borrowing his scanner to check it. He laughed- his suburban trans hits that temp with a load going up that mountain frequently- We ended up selling that suburban because the wife found a smokin deal on a new escalade (suburban with a different sticker) with a 6.0 LS which had enough shiny new toy for her to make the jump. I wish I never sold that 01. Oh, spark plugs- you mean someone bothere to change them in a 6.0? Haha- if mpg drops then MAYBE- otherwise they run 250,000 no problem.
Before the suburban my wife had a mercury grand marquis that got oil changes at roughly 5,000 mile intervals because procrastination. We bought used with 30,000 miles on it, and the engine had to come apart at 70,000 because of it. Timing chain tensioner is oil pressure fed and they plug up at about 100,000 miles even if you use synthetic and best filter getting changed on time. Taxi driving father in law drove them and learned if you city drive in overdrive the trans goes at 150,000 but only use od on hiway they last 300,000. The spark plugs are needed in that engine at 25,000 miles. He sang praises because the ride was as nice to my wife- after we bought it - then told of the trans issue. Gave the car to my father in law after the engine repair at about 72,500 when we bought the suburban...
The LS 5.3 and 5.7 are awesome engines IF and only if you turn off the cylinder cancellation system that proved so bad they kept changing how it worked and the name so it’s recorded issues wouldn’t affect new sales. MPG In a empty pickup: 5.3, 5.7, 6.0 best in that order. But weight of suburban with 800# of humans/ gear in any combo and they all 3 get same. Drive fast like my wife and I do- typical city driver racing out front, freeway 65 translates to 80, etc, and the 6.0 drops 1 mpg but the other drop way lower. Put 1,000# in a 5.3 and 1200# in the 6.0 suburban and the 6.0 gets 2mpg better on the same trip following each other, consistently. (Large extend family and many of us own suburbans to compare).
So what the vehicle is and which engine/ trans it has makes all the difference.
I never buy new vehicles. 90% of the time, only buy ones I can find fleet history of high mileage use for cost estimation. I used to enjoy working on cars/trucks. Now I hate it most of the time. My Hummer and the 43 Willy’s is the only exception- and really the mundane maintenance of the hummer i don't like anymore. So that influences why I pick what I do. If frequent maintenance is ok or fun to you- that makes a big difference.
