MPG is all very well and good, considering that most people that are concerned about their fuel consumption tend to want to get as many miles as they can out of it before they need to fill up again. However, I was stuck in traffic recently averaging a rather measly 4.3 MPG simply due to the fact that I had the engine on whilst I was scraping the ice off the car before I left as well as being in a lot of stop-start traffic when I did, hence not accumulating many miles for the duration of time that the engine was turning over. That does not necessarily mean that the car was inefficient, just that I wasn't able to complete that many miles per gallon.
What is the best alternative metric that I can use to be able to find or calculate the actual efficiency of the engine?
Also, how can I find out what this metric is on my car? Can I do it through the OBD-II port?