car habits that hurt your engine

2 and 3 depends on what type of engine it is and the year. The materials the engine is made of makes a big difference then the climate you live in. Most newer none diesel engines yes the raving is bad. Idling all has to do with the type of transmission. If it's got a manual transmission it's not bad. However with Rams the fluid don't coat the engine correctly while Idling for the 5.7 gas 1500's. However this is more of a design flaw that Ram never fixes. It's not the same with all gas engines. Ford's are also known for Carbon buildup. It's designed flaws that usually cause issues with Idling. Hybrids don't have the issues Idling in traffic nor do standard transmissions. However if the transmission has a torque converter yes it will cause issues but theirs ways to avoid it while idling. Going on the freeway once a month to let it rip once your engine is warmed up. Will help with Carbon buildup. Also buying gas that don't have good cleaners will cause carbon buildup.