Ever since getting my HCH 8 months ago, I've found myself focusing on the tachometer to maximize FE. For example, 2000 rpm seems to be the "sweet spot" at 55-60 mph -- 60-79 MPG on level roads, 80-90 on slight downgrades. Similar FE is obtained with ~1800 rpm at ~45 mph. On the rare occasions that I drive the Fla. Turnpike (speed limit 70, but I don't exceed 65), the best FE seems to be at ~2200 rpm. Unfortunately FE decreases the ~10 miles nearest to home, as the terrain becomes very hilly (and more uphill than down).

 

the instaneous mpg read-out works better for me in maximizing FE than the tachometer - it's more clear of a readout than finding the rev sweet spots for each individual speed on a certain terrain and incline. but, to each his own

 

I use the instantanious FE gauge. I only use the tach to make sure I'm not reving too much. 2100 is what I set as my max and thats only while accelerating. I will drive around 1500rpm and slowly loose speed and then accelerate at 2100-2300 rpm to get back up to speed.

 

I don't see much RPM difference between.....say 40 and 52MPG but I do see a 12 MPG difference

 

I think this is key. While accelerating, especially from a stop, the tachometer is more useful than the FCD, because the FCD has fairly low resolution, and a slow refresh rate so it's difficult to pick up sudden changes. A few bars on the FCD at 1800RPM and holding vs 2200RPM and rising is a big difference that might not show up right away on the FCD. However, when cruising, a little bit of feathering makes a much more noticable difference on the FCD than the tach.

Another situation where the tach can be nice for the truly obsessive is for faster N-coasts, such as on surface streets with ~50mph limits on a gradual decline, where it is nice to let the tach settle into the highest gear it's willing to go, then go into neutral and maintain speed with the engine at idle, then re-engage at just the right level for a perfectly smooth re-engagement.

 

Personally, the only thing I use the tach for is while shutting down for a FAS.

I let the RPM settle below 1K before shutting down to avoid a ping upon restart.
I'm not sure exactly why it is so, I guess it gives time for unburned gasses to exit the exhaust pipes.