what's this universal mpg gauge - vacuum??

[MetroMPG]

anyone know anything about this JC Whitney item?

# For all cars, trucks, vans and RVs

# <b>Miles-per-gallon scale shows actual gas mileage as you drive</b>

# Easy to install on or under dash

catalog link: http://tinyurl.com/o2tur

[Matt Timion]

My understanding is that it is just a vacuum gauge with MPG numbers on it. I remember wanting to purchase one of those a while ago but changed my mind when someone told me that these things don't work too well on non-carbureted engines.

[MetroMPG]

if it's a vacuum gauge, carburetion vs FI shouldn't affect it. it's all about manifold vacuum, regardless of how the fuel is delivered. (wouldnt work on diesels though)

for it to show mpg numbers, you must be able to calibrate it somehow.

too bad the picture's not clearer. i'd like to see what's written on the gauge face.

[krousdb]

Originally Posted by MetroMPG

if it's a vacuum gauge, carburetion vs FI shouldn't affect it. it's all about manifold vacuum, regardless of how the fuel is delivered. (wouldnt work on diesels though)

for it to show mpg numbers, you must be able to calibrate it somehow.

too bad the picture's not clearer. i'd like to see what's written on the gauge face.

I think that the outer ring rotates so you can set a certain MPG value to a vacuum value. But vacuum is only one piece of the puzzle. The other piece is speed. This is just a fancy vacuum gauge without any vehicle speed inputs.

[philmcneal]

Originally Posted by krousdb

I think that the outer ring rotates so you can set a certain MPG value to a vacuum value. But vacuum is only one piece of the puzzle. The other piece is speed. This is just a fancy vacuum gauge without any vehicle speed inputs.

damn i was about to buy it too, 28 bucks to show my fuel economy!?! but ya i need vehicle speed inputs too! and mpg average.