Here's what an engine designer says.

“The California Air Resources Board and the E.P.A. have been very focused on making sure that catalytic converters perform within 96 percent of their original capability at 100,000 miles,” said Jagadish Sorab, technical leader for engine design at Ford Motor. “Because of this, we needed to reduce the amount of oil being used by the engine to reduce the oil reaching the catalysts.

“Fifteen years ago, piston rings would show perhaps 50 microns of wear over the useful life of a vehicle,” Mr. Sorab said, referring to the engine part responsible for sealing combustion in the cylinder. “Today, it is less than 10 microns. As a benchmark, a human hair is 200 microns thick.

“Materials are much better,” Mr. Sorab continued. “We can use very durable, diamondlike carbon finishes to prevent wear. We have tested our newest breed of EcoBoost engines, in our F-150 pickup, for 250,000 miles. When we tear the engines down, we cannot see any evidence of wear.”

-----

“Competition is part of it,” said Peter Egan, a former auto mechanic and now editor at large of Road & Track magazine. “Japanese cars kind of upped everyone’s game a bit. With some exceptions, the engines would go a long time without burning oil or having other major problems.”

Hyundai and Kia, the South Korean carmakers, now include 100,000-mile/10-year warranties on their cars’ powertrains. If a relatively abusive driver can count on no major mechanical failures before 100,000 miles, a careful owner can — and does — expect his car to go much farther.

“My parents, with their ’56 Buick, used to have the wheel bearings repacked with grease before a long trip. Nobody does that anymore. The lubricants are better, the machining is better.”

from:
http://www.nytimes.com/2012/03/18/automobiles/as-cars-are-kept-longer-200000-is-new-100000.html?_r=0

What are the main reasons that newer high performance engines can go much longer without a total rebuild than older engines we build? For example, the 485hp SRT challenger motor compared to a fresh built 500 hp aluminium headed 440 running less than 10.5:1 compression. . In most cases the 440 would need a rebuild or at least bearings and maube rings at a much shorter interval than the 392

Without a doubt overdrive transmissions is the biggest factor.

EFI is better yes, but even they have to get run out on the highway to "blow the carbon out" every now and then.

I don't know about the significance of overdrive. Lots of new 4cyl cars still buzz at 3000rpm down the highway and they have to still meet the same standards of longevity as lower revving engines.

I had a 1985 Nissan 300ZX that I put 315,000 miles on with factory recommended maintenance, i.e., 3000 mile oil changes. I finally let it go because it failed a state emission test after 25 years. I currently have a 2000 Toyota Camry V6 that has 318,000 miles and passed it's last emission test and is still going strong. My guess is that lubricants are much better and the metallurgy of engine components also has something to do with it.

My $.02.

What are low tension rings?

I'd like to hear more about Lead vs. lead free gas. I always thought it was a lubricant for the valve train and valve seats. Today they use "hardened" valve seats eliminating the need for lead in gasoline, but my 340 does not have hardened seats I was told I need to put a lead additive in to prevent wear.

Moparts Mythbusters.... What's the true story?