Which technique gives better mileage?
 

Car is 1995 Toyota Corolla, 1.6 l auto, in good condition. Starting gently from a stop, the car shifts up to top gear rather quickly, about 20 mph. I need to reach my normal cruising speed of 51 mph, torque convertor is locked up at that point, and I am in no hurry to go anywhere.

Which would yield better gas mileage ?:

A. from top gear, at about 20 mph, accelerate very slowly, just enough to keep the speedometer rising until I reach my cruising speed. Sometimes this may take up to a minute. Watch vacuum gauge and keep vacuum as high as possible, usually above 5 inches.

B. from top gear, at about 20 mph, accelerate moderately hard, without letting the trans downshift, until I reach cruising speed. Obviously this will happen quicker than one minuet as in scenario A. Watch vacuum gauge, but under this technique the gauge would go to zero.

I'd expect B to. Harder acceleration is less acceleration.

I agree - B is better. BSFC wins.

You should do best in an auto by acelerating as fast as possible without delaying transmission upshifts. This gives you the highest practical load, which in turn gives you best BSFC. If you can't stay in top gear (converter locked) then pulse (engine on) and glide. No engine off when moving in an auto, or you could hurt the transmission.

regards
Mech

My guess is also B, brisk acceleration.

I recently played on the back roads, taking the engine to the end of the redline, and I got one of my best mpg scores. Of course, I wasn't touching the brakes for anything, but instead coasted. It didn't seem to affect mpg as much as I thought it would.

If you engine off coast, then the engine is only working to get you to speed, so the amount of fuel used to get you there is the major factor in MPG, aero being second (first if you go about 50 MPH). hard fast acceleration tend to be at the ~80 load where the engine is most efficient. so your example sounds about right.
I would stop just short of red line though :)

I also would go with B in my auto i seem to get my best mpgs at 70-80% engine load

I'll start employing EOC when covering distances of 1/4mi or more. I've been leaving the engine on, but there is no reason to do so in a manual since I can bump start.

I normally accelerate at 85% load and shift at 3000rpm. I'll cruise at around 1500rpm.

The V-Tech kicks in at 6000rpm and the maximum rpm is 7500. I was just playing since I have never seen what my car is capable of. No sense driving a sporty car if you don't have fun with it every now and then. :D

Mcgiiver -

This would have made a great poll :

CarloSW2

No, you were being responsible. The gliding deniers keep pointing out how dangerous life is when you're not in gear (if your engine stalls, you lose power steering and the ability to accelerate away from danger). Familiarizing yourself with that safety feature called acceleration is only making you more ready to use it to avoid a hazard. :D

I am trying to figure this out as well.

On my on dash fuel consumption readout, I have the ability and can accelerate with the readout at 5.6L/100km all the way until I reach highway speed.

Without a scan gauge I should still accelerate briskly until highway speed is attained...even if it puts me at 12-18 or even 25L/100km??

I don't understand how this could yield me better fuel economy. I have the same commute everyday, I have a setpoint on the road where I usually reach highways speed. I reset the average gauge at the launch point and do a test between the two and I always always get a better average going the easy 5.6L/100km up to highways speed.

I get how efficiency in engines work for the most part, but read outs are what they are and I have different findings. Is this 70% load goal for those that don't have the luxury of working their way up to speed like I do?

A few good experiments beats hours of theorizing.....

I tested this in my truck by looking at the trip mileage at a certain point on the way home from work. I tried various combinations of shift point and throttle opening, and ended up shifting out of first at about 2000 RPM, and at 2500 RPM in the higher gears. Gas pedal is halfway down, for about 12 to 13 lbs MAP. If I do everything right, I can be over 10 MPG at about 1/2 mile from a cold start on a warm day.

Nothing better than testing for yourself. Take a 5 km stretch of road, for the most part the higher the load (right up to floored) the better the load for most efficient acceleration (based on my reading of this site) the key is not reving the engine to high, somewhere between 2100 and 2700 rpm are what I guess is best for your engine/tranny combo. Rest your gauge, 3/4 floor it till 2100 rpm, let it off, floor it as hard as you can without it down shifting, once it its 2100 rpm, ease off and repeat untill desires speed is reach, finish the 5 km and record fuel usage. Repeat using 2300 rpm, then 2500 rpm, then 2700. Find the sweep spot and narrow in for the optimum.

Record your data and share, your hour of good testing is great data for everyone to learn from.

All the therory and testing by others only goes so far.

Edit: make sure the car if fully warm before starting, and do everything 2 or 3 times is even better.