A theoretical what if question

[gumbyk]

When I was involved in budgeting maintenance costs for helicopters, for an LTS101 engine, we were provisioning approx $150 per hour for overhaul and lifed items. (Not routine maintenance, just overhaul/finite lives)and just over $100 per hour for fuel. We were able to do the overhauls in-house, so that price is somewhat lower than retail.
Fuel, while a major cost, is not a major driver for re-engining programs.

Jets cruising at 300 mph? maybe, if they are running ahead of schedule, and don't want to get to destination early, but flying at less than optimum speed burns more fuel per mile travelled. It may seem as if they slow down, but really they are at a normal cruise speed.
As for how often a car engine needs maintenance - what happens if your car engine fails?

 

[Shortround6]

Even a low powered compact car "cruises" at 1/4 or less of max power. Car engines, when used as boat engines (work boat) or stationary power plants are limited to somewhat less power than they were as car engines in order to extend life.

 

[Jabberwocky]

There is not much speed with the Jets anymore because as soon as the climbout is done, they back way off the throttle, and slow way down. I've watched some of the high flying contrail makin planes and figured they were barely at 300 mph, and yes that is estimating the distance they moved in a certain amount of time.

Lol. Whut? You observed an aircraft flying at 25-35,000 ft from a fixed point on the ground with no other points of reference available and think you made a valid speed judgement?

Do you fly internationally at all? I've got a Sydney-Abu Dhabi flight next week. The distance is 7500 miles. Trip time is projected at 14 hours 20 minutes, so an average speed of about 525 mph.

If the A340 they're using really travelled "barely at 300 mph" then it would take 25 hours.

Hell, I flew Sydney-Gold Coast three weeks ago. Flying time on a 450 mile flight was just over an hour, and that includes about 25% of the flight spent climbing or descending for landing.