[RedDevil]

Originally Posted by wobombat

2. Is the inability to hold compression in older cars a major factor in preventing good MPG when doing P&G?

3. Do some automatic trannys lock up the torque converter to slow you down in the manual low gears?

thanks to anyone who has insight here.

I have an Insight you're welcome

@2: If the compression fails new piston rings or valves/valve beds are needed.
The % of loss remains the same no matter the pressure (more lost at higher pressure, but also more that's put to use), but it will be larger at lower revs as it gets more time to escape then. So definitely something to look after if you go eco.

@3: I believe lock-up means that the input and output shaft lock together by a special clutch so both halves in the torque converter spin at the same speed. When they aren't locked the output shaft will turn slightly slower than the input shaft, wasting power.
Lock-up would allow your car to hold the same speed at slightly lower engine revs at the same load. AFAIK it has nothing to do with engine breaking or slowing down.
Says the man who only has driven manuals and CVT's, apart from a 3000 mile trip in a Ford Tempo with a very bad 2½ speed...