Best way to calculate avg speed for tank?

[Vekke]

What is the best way to calculate tanks avg speed. SG II does it automatically, but it calculates the speed so that it doesnt give good impression of how fast you have travelled on highway. The problem is that avg speed starts to drop rapidly when driving in town.

So have you figured out good way to do it? In my opinion good way should be that after every long trip you write down the avg speed and the distances tarvelled. Then in next fillup do little math to calculate avg speed for highway driving...

[skyl4rk]

I think average speed should be documented in each Fuel Log, it is important to know to compare results.

I have started using the Tank average speed and noting it in my log.

What is the issue with the Scangauge tank average? I have to admit that I avoid high speed highways and stay on country roads and local highways. Is high speed highway fuel efficiency your main interest?

[Daox]

The SG calculates average speed over an entire trip, not just while moving. So, if you are stopped at a light it is still calculating average speed. This really is the only way to go. I dunno why you'd only want average highway speed.

[MetroMPG]

One reason I'd want to know average "driving" speed is it gives a person a more accurate picture of how fast you were actually going to get the mileage you got. (Assuming you weren't wildly all over the map, speed wise.)

My actual average driving speed in the Green Grand Prix fuel economy competition (calculated: distance driven/time moving) was 45 mph. But the ScanGauge reported an average speed (including time stopped at lights, signs, mandatory rest stop) of 37 mph.

[ConnClark]

If you are driving a tank mileage is your last concern

[Vekke]

I also put down the SG tank average speed, but it only tells me "something" about my aero modifications/consumption directions.

lets say that I do new front bumber for my car and I want to know if it is any better than the last one. I could do some ABA test but I burn fuel by doing so, not good for in my opinion. At the moment I see that it is best way for me to compare results is by tank consumption. Well tank consumption figures are ok but I normally dont drive my usual highway driving the same way every trip. There are many things that effect to my speed.
1. Am I in a hurry. (not often) speed ca 80mph
2. Is there a good big car to follow at speed what I am comfortable of driving. Speeds usually between 60-75mph
3. Is there any cars to follow. speeds 60-70mph

Well depending on these situations how I have driven the trip my avg speed for my normal highway trip is usually between 47-57 mph. I would like to know how my highway speed affects to my tank consumption. I cant trust my SG readings because I have calibrated it so that it tells accurate reading when I am using full push and glide technique for the whole tank. When I am driving speeds below 55 I use different techigues and so my SG accuracy starts to go bad.

Lets say I drive full P&G at avg speed of 50 mph SG shows me a reading ca 84 mpg.
60 mph is ca 71mpg
But when Im driving in the other driving method speed of 75 mph my consumption figures may be something like 39 mpg so my consumption have doubled!!! I know the real figures should be something like 52 mpg...

[The Atomic Ass]

Originally Posted by MetroMPG

One reason I'd want to know average "driving" speed is it gives a person a more accurate picture of how fast you were actually going to get the mileage you got. (Assuming you weren't wildly all over the map, speed wise.)

My actual average driving speed in the Green Grand Prix fuel economy competition (calculated: distance driven/time moving) was 45 mph. But the ScanGauge reported an average speed (including time stopped at lights, signs, mandatory rest stop) of 37 mph.

I would have thought it would stop counting at the rest stop, after it noticed you were stopped for a significant period of time?