Quote:
Originally Posted by speeder
Wow!!! That is amazing! Does mpg seem to be as good at 67 as well? Just trying to figure out if there's anything to this 62-67 sweet spot. I'm just half way thru my third tank of gas on my new/used si. Wanted to get a couple more tanks under my belt before I get the scanguage so i have something to compare with/without cost benefit.
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I doubt there's much to the "sweet spot" idea, at least with a car like ours that actually has a very flat torque curve, especially in the RPM band we're talking about (2000-3500 RPM). Experience seems to show that once I'm in 6th gear my MPG falls off more quickly with each increase in speed which makes sense since drag will increase four times each time you double speed. A few weeks back I drove a ~10 mile flat stretch of road that has maybe 200' of descent and one overpass at 57 MPH with a neutral coast down to 35 MPH the last two miles as the speed limit fell, windows closed, A/C off and a fully warm car, upper 90's outside, 47.X MPG.
The general rule of thumb is that the lowest speed you can use your lowest gear in will yield you the highest MPG on a flat road that doesn't require you to accelerate.
The ScanGauge will help you with this if you know what to look for. It takes time (and research) to figure out what you need to do to wring out maximum MPG for a given speed. I've been working hard at this in my Si for 5 months and did some work at this for the previous couple of years and I'm STILL finding little things that seem to make a difference in fuel economy.