which has better fuel efficiency?

Car A: City 19/ hwy 29/ Comb 23 MPG

Car B: City 15/ hwy 20/ Comb 17 MPG

which one is more efficient and how big is the difference?

So I watching that movie The Fast and The Furious and I noticed they had these bottles in their car called NOS they usually hit the button at the end of the race.

My question is

Why don't they just hit it at the begging of the race?

Why don't they just hit it the entire way?

Is a car with cold air intake the same as using NOS the whole session?

Other than an obvious leak why would only one tire lose about 5 lbs of tire pressure in the summer months ?

This is a new car 1000 miles and the pressure has remained stable after a 25 mile trip following the tire sensor alert and verified correct by a tire pressure gauge, it is a rear mounted driver side tire.

bought a car recently ('10 Accord EX-l V6 6MT) that the dealership seemed to kind of neglect. as if they listed it but weren't ready to sell. they didn't wash the engine before they gave it to me, which they lied and said they were going to. they didn't fix a scratch they promised to. and they didn't replace a missing clip on the bumper.... that they said they were going to. they claim all of this would be taken care of when i brought it back in to have the hood repainted. why it needs repainted... i do not know.

this instantly left a bad taste in my mouth.

then, during my hour long trip to work, i get off the highway and the clutch is creaking upon release. its gotten worse every day. they have yet to respond to me as to whether or not my warranty will cover a clutch, so i'm having the car looked at by my usual garage.

upon further research, i found out that it has an aftermarket lip as well. this raises the question "what other aftermarket parts was i not told about?". this is serious since my warranty may already be voided due to an installed part, or could be voided if an issue occurs because of an aftermarket component.

they sold it to me at stock price, so i'm getting pretty heated. if my shop finds other aftermarket parts, do you think i have a case against the dealership? i honestly think i should be reimbursed for any missing stock components, as well as have a third party do any needed maintenance, paid for by the dealership.

in an automatic there is always going to be some slippage. in a manual (or any car with a clutch), there is a direct physical connection or complete disconnection of the engine to the gearbox and rest of the car.
in an automatic there is a fluid coupling active at all times be it at a standstill or moving. there is never a complete connection or disconnection.
when you start moving in a manual if you are not skilled you'll release the clutch fairly quickly and the car will either jolt forwards and possibly stall. this is the result of a complete disconnect to a complete connection and the engine's torque. in an automatic there is a fluid coupling that "connects" the engine to the gearbox. the engine is always putting stress on the gearbox as long as the car in in Drive and not coasting. this is why when you let off the brakes from a stand still the car will move even without adding gas.
when you shift gears in a manual there is a switch from a direct connection to a complete disconnection during this time, the engine changes speed fairly quickly due to its compression. when you reconnect the engine to the gearbox after changing gears the engine and gearbox may not be going at matching speeds in which case either the engine will be forced to speed up or slow down where you will again feel that compression. if you could perfectly match the engine and gearbox speed when the tme comes to re-engage after a gearshift you won't feel anything.
meanwhile during a gearshift in an automatic since the fluid coupling is present there is less of a difference in speed between the engine and gearbox (that difference will be equalized almost completely by the fluid coupling) which means you don't feel that much of a jolt.

when you reprogram an automatic to have more severe shifting, the shift speed increases and it doesn't give the fluid coupling enough time to match the 2 different speeds. a reprogrammed automatic feels much more jolty because the engine and gearbox are moving at different speeds and are forced to match like in an automatic.

edit: i just realized that while the term fluid coupling is easily understood by me others may not know what they are. check out this video that explains what they are and how they work. i know its old but it does a great job.

what do i do if i scrape someones car in a public parking lot and theyre not there?

it wasnt a bad scratch but i still felt horrible. they werent around and i had to catch the bus but i really didnt want it to be a hit and run so i parked near them. i really do feel awful about it but i didnt know where they were or when theyd get back. what do i do? if their car is still there when im back do i leave a note or something? and if so what do i say?