I think it is more about being not psychologically acceptable to downshift for passing or on 5% highway hills, and this is not Mitsu only, all cars offered with auto and manual have the same issue.
Originally Posted by Tinker1980
To complement this good post on wear, there are a couple more dimensions to consider:
1) 80-90% of the engine wear happens during cold start, when you have cold oil which doesn't wanna flow, time delay for oil pressure to go up and dry metal to metal contact. Using oversized filter and 0w20 oil helps, but still. To reduce this mfg going to electric oil pumps which pre-pump oil prior to start.
2) many engine wear issues especially on OHV engines are related to valve gasket condition. After 5-6 years they harden and start letting oil pass on intake valves. That if left alone will destroy engine in 20-30k.
View my fuel log 2015 Mirage DE 1.2 manual: 46.4 mpg (US) ... 19.7 km/L ... 5.1 L/100 km ... 55.7 mpg (Imp)