New Toyota engines are smaller but better; my question is 'by what metric?'

Okay, sure, they're more efficient, which is great, but how long will they run between major repairs? Are they 300k mile engines before significant malfunction? If we factor that into account, then the efficiency goes down rather precipitiously, I would expect.
Let's do a bit of 'rithmetic, shall we?

If I have to replace a $5000.00 turbo after 150k miles, that is a dollar every 30 miles, or a dime every 3 miles, or about 3 cents/mile.
https://goldfarbinc.com/blogs/news/how-long-do-turbos-last

If the new Tacoma averages 23mpg, and Gen 2 average 15, that is a difference of 8 mpg. At $4.00/gal, it is a difference of $.50/mile. (2024 Tacoma official data, which is VERY generous, I would suspect. 20 is probably much closer to the actual average.)

So, yeah, assuming the new Toyota engines last for 150k miles without major engine work, it is a better scenario, until you factor in the cost of the vehicle itself. My Tacoma is $25K. A new one of equivalent capacity and trim is $45k.
That means a difference of $20000 or 5000 gallons of fuel, or...... 75000 miles of driving.
I'll keep my nice, simple, naturally aspirated 4.0L v6.

Edit:
Of note, I an a dyed in the wool environmentalist. Also, none of the above takes into account externalized costs like underpaid labor to mine or refine materials, pollution from the vastly higher quantities of energy necessary to create incredibly efficient engines, etc.
I will say, as soon as I can crank out 500 miles towing 2000Kg on an electric vehicle and get 200k miles before changing the battery, I'm in like Flynn. Until then, again, I'll keep my torquey and reliable 2015.

 

Going turbo wasn’t about longevity on Toyotas end. It’s about lower emissions, similar or increased outputs while providing better fuel economy.

The average vehicle ownership is 8 years, 6 years for Americans. That means the average person isn’t going to give a damn about high mileage repair costs. Toyota isn’t going to give a shit either as long as the vehicle survives it’s warranty period.

People who buy used might see this as a red flag and may shop other brands but the reality is all modern manufacturers are following suit with going turbo, why? Because they have to if they want to continue selling units that pass epa standards and get better fuel mileage than a 1990 mid size truck.

In a couple more years when standards change again we can all gripe about the maintenance cost of hybrid trucks vs the cost of forced induction.

 

The one issue is the truck is still heavy as well, I attribute it to the full frame, the body work is all aluminum but in the end its roughly the same weight as the outgoing 2nd and 3rd gen.

So the best they can do is reduce emission output with a smaller engine.

EPA MPG testing is also hard to confirm, I am still waiting to see what our customers are averaging.

The truck frame sits slightly lower but theres still a massive negative air gap under the truck, the dam helps, but in the end a lower slung truck like the Nissan Frontier may help as well.

Longevity? It's a Toyota, even if there's a problem it will likely be addressed. The 3rd gens only had one issue that was never truly resolved. 2nd definitely fixed all issues from early years, except rust.

 

My 2013 4x4 routinely gets 20 mpg if I do my part. I expect it to reach 300K with routine maintenance.

 

Very well put o,p.
It comes down to when to bail from a new vehicle,.. and overall to cost per mile. Now more than ever. Unfortunately most new high tech. Is focused more on emmision and mpg numbers. Reliability/durability is traded off for unachievable pipe dreams. Turbos can be fun. Turbos can be efficient. But usually not both... Except with a trade off. Theres no replacement for displacement!

I'm a 63 year old car guy and have seen cars in general have common blocks of good years, then go back to blocks of bad. Repeated cycles as tech evolves (devolves?). We are presently in the bad cycle. (in general).

Try owning a VW/Audi as an example. The million mile air cooled motor is replaces with a medical grade oxygen pump that is lucky to see 100k. My flower farting 2011 TDI SportWagen 6 speed manual was AWSOME... while it worked... 45mpg, sporty, everyone loved them... resale was sky high. Then eventually came the inevitable and multiple 2k$+, complicated high tech repairs. Resale plummeted. Luckily I timed it right and got out and into a "low tech" 2nd gen Tacoma. (IMO the last of the high cycle)

A maintenance only 300k 14 mpg normally aspirated truck can far less expensive to drive than a high tech 70k, 45 mpg TDI Sportwagen when "over tevhnology" fails. It cost $$$!

 

I think your math is a bit off. The difference between 2nd and 4th gen can’t be $0.50/mile. My 2020 has averaged $0.37/mile this year at over $6.50/gallon Canadian ripoff gas prices.

 

I agree this is more accurate. I have tracked 9,736 gallons of fuel on my 2g with an avg cost of $2.95 and my cost per mile is 0.196

 

I will add that with this new drivetrain and 8-spd auto we are more in control of fuel useage. With the ‘22 V6 I could baby it and only get 8 litres per 100 km on my daily 27 km one way drive. Same route I have achieved 6.8/100 on this 2.4, only rarely but it is possible.

 

Good catch. The 50¢ per mile is a mistake: that's the cost of getting 8 mpg.

$4 per gal / 23 mpg = 17.4¢ per mile
$4 per gal / 15 mpg = 25¢ per mile

Which is a savings of almost $0.08 per mile, in the most extreme case, so it's even worse than OP figured, lol. And let's be realistic, if you're getting 15 mpg in a 2nd gen (which is rated for 16/21 for a 4wd, I think), you're not going to automatically get 23 mpg in the 4th gen with the same driving habits.