With 78k miles I'm willing to bet the headgaskets have never been done and are leaking oil. That would contribute to the low oil level which took the engine out.

What?!

 

 

The modern engine has to deal with emissions, power, and heat. The hotter you can the cylinder, the lower the emissions (more complete burning) to be simplistic. To help with a faster warm-up, again for emissions (and performance), pistons have gotten lighter and thinnner. They heat up faster and move more easily (this is why piston slap is normal when cold in so many engines). The trade off with less mass and hotter running is the ability to remove heat from the piston.

 

The advantage of this on engines (N/A) is to allow you to use regular vs premium fuel on some engines. On forced induction it keeps the pistons from over heating. Some engines have specific squirters just for this purpose, others do it by simpler means. What people tend to blur is the lines of high performance over every day engine. Almost all small engines today are "high" performance. There is a hell of a lot of power being squeezed out of relativly small engines. 2.5L is a 152 cubic inch engine making 170-175 HP. If you convert Liters to cubic inches it gets more amazing as to how much power is coming out of standard 4 cylinder engines.

 

1.6L = 97 CI (Mazda 3 110 hp)

1.8 = 109 CI (Chevy Cruze 138 hp)

2.0 = 122 CI (Mazda 3i 148)

 

Wasnt all that many years ago where a 4cyl of any type was hard pressed to break 100HP, and a 1.6 had HP raitings of 80 or less.

 

 

 

As Emissions got stricter, and as they will continue to. some engine will use engine oil to help cool off the piston skirts and beneath the piston. This oilis very minute in it's amounts, as a little oil can do a lot of work It's the evaporation of the oil that removes the heat. This is actually why PCV valves have become more important. Oil mixed fumes will gum them up over time, where it used to be the PCV only dealt with and blow-by from the rings.

 

If you have a rotary, deisel, or forced induction the oil consumption can even be higher as per design. This is why oil burning and oil consumption are two different animals.