One day later: 100+ mpg round trip!

[BabyDiesel]

I finally did what I thought couldn't be done. I got 62.0 mpg this morning, which included an extra 0.6 miles to McDonald's. Then the trip back... 139.4!

Averages out to 100.7 mpg

I week ago, I was getting around 65-75 mpg roundtrip, and 75 was tough! I'm taking a whole different approach, in which my max speed is under 30 mph. Today, I left the stoplight to begin my downhill desent, sped up to 17 mph and EOC the rest of the way. The hill took my speed to 28 mph, and that was exactly what was needed to never turn the engine back on.

[RedDevil]

Nice!

But you cannot take the average mpg of 2 trips by counting them together and dividing by 2.
You could if both trips are same distance and the reading was in gallons per miles instead of miles per gallons.

So we can get it together: 62 mpg is 1.61 g/100 miles.
139.4 mpg means 0.72 g/100 miles
You averaged 1.165 g/100 miles, which is 85.84 mpg.
Impressive. But not triple digit stuff.

[puddleglum]

If you're still using your scangauge, or if you can change your dash display, try setting it to metric. I know it will take some getting used to, but L/100 km will be easier to track daily mileage without the error that RedDevil pointed out.
I agree with you that too much speed and accelerating too fast kills the short trips.

[BabyDiesel]

Oops! Thak you RedDevil for pointing out my blunder I was in to much of a hurry and didn't compute the numbers correctly.

Thanks for the tip Puddleglum. I have used l/100km before to track mpgs, I simply can't get used to it. What I do is track mpgs there, and reset it before leaving work. Getting the SG to accurately reflect mpgs has been difficult for no other reason than my own laziness

[puddleglum]

I like the SG because it tracks tank,trip and daily mileage so there is nothing to reset really. It does take some work and time to get it dialed in initially to read correctly, that's the downside, but I just follow the daily mileage and check the trip when I think it might be extra good. You have the advantage of comparing your SG to your on board one. Should make dialing it in pretty simple.

[BabyDiesel]

I have used and loved how the SG tracks mileage by trip, tank and daily. The Insight's extremely accurate FCD has made me lazy as I admit, and I'm usually rushing after fueling. I got it one step closer tonight, so hopefully it will be right soon.

RedDevil, I calculated a daily mpg of 94.25. Here is how I came up with it:

62.0 mpg to work over 1.5 miles, plus extra 0.6, = 2.1 miles
139.4 mpg to home over 1.5 miles = 1.5 miles

Now, I make the assumption that since I averaged xx.x mpg over x.x miles, it is essentially the same thing as getting xx.x mpg across every 0.1 miles of travel.

2.1 miles = 21 tenths of a mile
1.5 miles = 15 tenths of a mile

((62.0*21)+(139.4*15))/36

36 is the total tenths of a mile driven roundtrip.

This equation would give a trip average of 94.25 mpg. Thoughts/corrections sir?

[RedDevil]

Originally Posted by BabyDiesel

RedDevil, I calculated a daily mpg of 94.25. Here is how I came up with it:

62.0 mpg to work over 1.5 miles, plus extra 0.6, = 2.1 miles
139.4 mpg to home over 1.5 miles = 1.5 miles

Now, I make the assumption that since I averaged xx.x mpg over x.x miles, it is essentially the same thing as getting xx.x mpg across every 0.1 miles of travel.

2.1 miles = 21 tenths of a mile
1.5 miles = 15 tenths of a mile

((62.0*21)+(139.4*15))/36

36 is the total tenths of a mile driven roundtrip.

This equation would give a trip average of 94.25 mpg. Thoughts/corrections sir?

Hi BabyDiesel,

well - we know the miles and mpg, we can work out the gallons and see if it adds up.

2.1 miles / 62.0 mpg = 0.03387 gallon
1.5 miles / 139.4 mpg = 0.01076 gallon
---------------------------------------------
3.6 miles ................. / 0.04463 gallon = 80.66 mpg.

That is still way better than my best ever single trip as indicated by the MID, never mind short round trips!

But it differs from your calculation. Which would be correct if you used gallons per miles instead of mpg.
The way you did it makes the higher mpg more significant in the result, while in reality the higher it gets the less it adds to the result.

It all becomes obvious when you exaggerate the numbers.
Take the hypothetical 20 mile round trip to the Very Steep Mountain.
The ascent is terrible: you manage just 1 mpg over the 10 miles to the top.
The descent is EOC and DFCO all the way except the get go from the parking lot. A whopping 1999 mpg is the reward.

Back down you do the math and find you averaged 1000 mpg for the trip, using just 0.02 gallon. But your tank is empty!
The ascent took 1 gallon per mile, the descent 0.0005 gpm.
The average is 0.50025 gpm. The real trip economy was about 2 mpg.

[BabyDiesel]

RedDevil, I truly appreciate you taking the time to break these figures down for me and explain everything thouroughly It took your last post for everything to make sense to me. I wasn't intentionally trying to exaggerate my mpgs, but the internal drive to break 100 mpg is strong and I am a very strong willed person to begin with.

That being said, I won't have chance to attain this goal. I lost my job Monday so I am back to job searching.. hopefully my next slavep.. err, workplace will have a mpg friendly route.

[RedDevil]

Originally Posted by BabyDiesel

That being said, I won't have chance to attain this goal. I lost my job Monday so I am back to job searching.. hopefully my next slavep.. err, workplace will have a mpg friendly route.

Ouch... Wish you the best, hope you'll find a good job soon!

[puddleglum]

That's tough, sorry to hear it. Hope something works out for you.