Are we getting anywhere?
In leaded gas days, the debate was whether you changed the plugs twice a year, or every 10,000 miles.
From '78 - '84 I drove a '68 Impala - 307 2-bbl, Powerglide, no air. It sat six. It typically turned in 19 MPG Imperial on the highway. That's what, 15 - 16 MPG US or 15 l/100 km? I bet the simple transmission w/o lock-up torque converter made for a lot of slippage. From 120K miles on, it burned a quart of Quaker State 10W-30 every 200 miles, with consumption increasing to a quart every 70 miles by '81. I had a spare set of plugs I would clean and swap in when the set in use fouled, every 200 miles or so. In '82, I swapped out the engine @ 176 K miles for a less tired 327 that burned a quart every 250 miles or so. The body was badly rusted when I bought it, and the tinworm defied my attempts to defeat it.
From '01 up 'til now, I've driven a '97 Mazda MPV. It seats seven. It averages 28 MPG Imperial on the highway. (23 - 24 MPG US, or 10 l/100 km.) It uses a litre of oil every 3000 - 5000 km. I change plugs every three to five years. It's got 304,000 km on the clock (c. 189,000 miles). The body is still pretty good, with just a bit of surface rust.
Yes, I think there have been advances in longevity. In fairness to the Chevy, it would have been run on leaded gas for its first 10 years at least, and I used dino in the crankcase (although I changed it every 2000 miles). The MPV has gotten all synthetics since we bought it 4 years old. The carburetor would dump raw fuel into the oil in the winter. The MPV's EFI & OBD II protocol help oil life a lot.
I could always repair the Impala by the side of the road. I loved GM's breaker points on the V8s. The fuel pump was easy to change. If the electronic ignition dies on the Mazda, it's tow truck time.
If I could somehow buy the Impala new, now, I'm sure I could make it last as long as the Mazda, but think it would always be thirstier than the MPV.
So, trade offs. I loved the character of the old Impala, and the styling.
