How to properly test modifications (AKA: don't believe every MPG claim you read)

[Nerys]

but he sees HIGHER mpg the higher the temps. that kills the AC thing.

I am just curious why I see almost NO difference and he sees such a HUGE difference over the SAME temperature changes.

now granted maybe I will also see a change now that I have a tiny car but as noted I have driven this metro in 80' temps and in 20' temps with NO apparent change in mpg beyond noise.

whats different between us? I live in PA (outside philly) and my commute is between 19057 (home) and 08215 (work)

I will have to start logging the temps as I drive.

how do you factor in the temp changes over the period of a tank? ie I fill upo every 3 or 4 days usually (multiple cars) do I just average the temps over the 4 days?

[MetroMPG]

Correction on my part: I mistook "NO" in your user info to mean you lived in New Orleans.

Trip length has a lot to do with the efficiency hit of ambient temperature. (The longer your trip, the smaller its impact.) How far is your daily drive?

Edit: Google Maps says 56.7 miles between those two postal codes. That would explain a lot.

[Nerys]

yeah 54miles actual each way I end up about 110 miles each day mostly semi city/highway

Here is a route plot that I have found the most efficient (the least number of stops all 50mph)

My Commute

I take precisely the same route in reverse to go back home. the start point is within a mile of home. yeah the no is when I was annoyed at sites asking for details so until I trust a site I fill in random stuff if it forces me to put something in IE no is "no" you don't need that :-) hehehe

what does it explain?

[Christ]

Originally Posted by Nerys

yeah 54miles actual each way I end up about 110 miles each day mostly semi city/highway

Here is a route plot that I have found the most efficient (the least number of stops all 50mph)

My Commute

I take precisely the same route in reverse to go back home. the start point is within a mile of home. yeah the no is when I was annoyed at sites asking for details so until I trust a site I fill in random stuff if it forces me to put something in IE no is "no" you don't need that :-) hehehe

what does it explain?

Glad to see you trust us now... :P

[gone-ot]

...and, there's also "engine break-in"...slowly but surely increasing MPG for no other (apparent) reason than accumulated age/miles...on both brand new engine and tires!

...also, I use "Olympic Scoring" where "highest" and "lowest" MPG values are discarded (to help reduce the "too good to be true" number flukes).

[PaleMelanesian]

I don't use the AC in the summer.
I also don't have "abnormal" trips in there, such as a fully warmed-up start.

[Mustang Dave]

Originally Posted by Old Tele man

...and, there's also "engine break-in"...slowly but surely increasing MPG for no other (apparent) reason than accumulated age/miles...on both brand new engine and tires!

Absolutely. My average fuel economy with my new Mustang was steadily increasing over time even before I found ecomodder.com and made adjustments to my driving technique and commuting route. I can only attribute that increase to engine and tire break-in. I'm not looking forward to the FE hit I'll take when I have to re-tire it.

[MetroMPG]

Good points about engine & tire break-in.

Originally Posted by Nerys

yeah 54miles actual each way I end up about 110 miles each day mostly semi city/highway

what does it explain?

It explains why you are less affected by falling ambient temperature than someone who lives in the same climate but has a more typical (shorter) commute.

54 miles is a long commute, and fuel economy is directly related to trip length. Google "fuel consumption" as a "function of trip length" and look through the results.

[luvit]

i'm selling all my chassis dynamometers and wind tunnels on ebay.

[gone-ot]

Originally Posted by luvit

i'm selling all my chassis dynamometers and wind tunnels on ebay.

...uh, was it something we said?