[Janizary]

Some anecdotal information posted in another MPG thread that really should have gone in this master thread:

Speed vs. MPG

With a 2% corrected error factor (i.e., measured against actuals on Trip / G), here are scan tool readings (measured at 2000' E, 80F, 1 occupant, HWY, 35PSI F, 32PSI R) averaged on 5 or more trips (each) of 70miles (and allowing CRUISE CONTROL to handle fuel delivery):

50mph, 6th gear, no inclines: 45MPG (Yes, it is, and yes, you can)
52mph, 6th gear, no inclines: 42MPG
55mph, 6th gear, no inclines: 38MPG
60mph, 6th gear, no inclines: 34MPG
65mph, 6th gear, no inclines: 32MPG

There are no 'I forgot to reset the trip' errors in there numbers. Nor do I have anything to gain or lose from reporting what the averaged figures are. I've been capturing, logging, and analyzing my gas figures on all my vehicles for several years. OBDII and good scan tools have made maximizing your MPG MUCH easier since you have live feedback of your fuel delivery, load, etc.

Other 'dedicated' SGII or other scan tool owners can easily verify these figures, given similar circumstances, proper calibration, use of cruise for fuel management, etc.

My 'in town' figures are not as standardized yet. However, I just changed offices and my trip to work will now be ALL surface streets. While the Si is not my daily driver, I will endeavor to take it to work a few times a week so I can log some realistic 'maximized' CITY figures.

I drive my wife's Pilot now and then and can get some rather amazing MPG in that vehicle as well by maximizing the VCM feature. 27MPG+ on road trips.

I wish I could do the same in my F350 7.3L super duty. Pretty much 12-14MPG regardless of no load, or pulling a 10K lb 5th wheel.

BTW, I can add some averaged readings for 70, 75, 80, 85mph if anyone is interested. The drops in MPG are quite dramatic.


'Your foot vs. cruise control'

In testing fuel delivery accuracy (as measured in GPH), there are very slight gradients in fuel use that can make a rather marked difference in MPG. For instance, letting cruise control handle fuel delivery on longer road trips vs. 'you'.

At some obscure point in the past I had noticed that (for example) at 1.1GPH I was cruising at 50MPH. Slightly (and I mean SLIGHTLY) hairing the gas to 1.2GPH I remained at 50MPH with no acceleration. Trying the opposite, I haired the fuel down to .9GPH and remained at 50MPH with no deceleration (all things being equal on level cruising surface). I played around with this off and on with 'my foot' as the input device, then decided to compare it to how cruise control handled fuel delivery.

The result: At most speeds I found cruise used between .1 and .3GPH LESS fuel than I did (i.e., 'my foot') to maintain exactly the same speed (again, all things being equal on the same level driving surface, same distances, etc...yes, I am sick that way; I seem to get almost as much fun gathering and analyzing data like this as I do at the Auto-X course over the weekend).

Again, this is on a manual transmission Civic Si. Results may vary substantially depending on the vehicle you use for comparison. On my wife's Pilot results are actually a bit more dramatic as VCM is involved and it cuts in more often when I use cruise to manage fuel delivery than if I am manually providing input via 'moe and joe'.

I am sure many folks will not have the patience to go out and drive the same 11 mile stretch (5.5 miles each way for this particular series of tests, I use a 70mile 'loop' for long distance tests) for hours on end, back and forth like I have done, just to get some numbers for comparisons and averaging. That's why you get other fools (like me) to do it for you. If you are sick enough, and bored enough (and you've got a good scan tool for data feeds), try it. You might find the data to be surprising.



"You and your Air Conditioner"

The Si's AC, for whatever reason, seems to be very consistent in the MPG loss at various highway cruising speeds. During last summer I compiled a bit of data on AC use on my test strip, and have been gathering a bit more data in the early part of this summer to try to nail down variations caused by higher temps (e.g., it is now in the low 100s, but will get into the high teens later in the summer) on my longer distance data points.

Overall, however, AC has a fairly consistent impact of ~3MPG when running at cruising speeds between 45MPH 55MPH. As speed increases the loss trails off a bit, down to about 2.5MPG or less at 65MPH. Obviously, this will have an even greater impact on city driving due to the increased fuel consumption, combined with the leach effect of the compressor.

Stopped and idling, fuel consumption runs .2GPH without the AC running. Turning on the AC bumps the amount to .3GPH. (Assuming the car is already warmed up. On a cold start idle fuel consumption runs from 1.1 to .4 until warmed up).

I've heard a few other SGII owners with auto Civics (R18, not K20) state a figure of .3GPH at idle with no AC and .4 to .5 with AC. So keep in mind this relates ONLY to the manual transmission Si. I'd like to plug my scan tool into someone else's Si to see if this is consistent. Perhaps at the next Vegas meet.

If there are any other SGII owners out there that are tracking this, I'd like to hear your feedback.