. When we were about to get out he noticed how much gas he had used just sitting idle. He has an 07 S550.I thought it was odd because we weren't moving so the engine had less of a demand for fuel. Am I correct in the assumption?
Yes and no. Yes, you are correct the engine has far less demand for fuel if it's just idling. That doesn't take a quantum physicist to figure out.
No, the gauge shouldn't have moved if you were truly in the car for only a few minutes. Now, if you "chilled" for an hour, that's another story.
I came home and got online and I read on another forum that a car that gets 19-25 mpg burns about one gallon of gas every 15 minutes.
I thought this HAD to be a mistake.
Wrong. I'd show you the math, but you wouldn't understand it. Besides, it's a pain to write equations in plain text. Furthermore, an engine will burn varying amounts of fuel at idle, based on engine capacity (size), not on how economical the engine is on the highway. Those two things are pretty much non-interchangeable.
For example, I can high idle (1200 rpm) a 6.4 Liter V8 diesel and it will go through 9 gallons every 12 hours, like clockwork. Of course, if I'm driving for those 12 hours, there is more load on the engine and it will use more fuel. But this isn't about driving it.
Point is, whatever forum you read that on, they are incorrect.
I know our cars don't get great gas mileage, but I find myself letting my car run while I talk on the cell and now I'm not sure if it is more advantageous to turn it off. What do you guys think about this?
If you're concerned about fuel, then it's more advantageous to turn it off because when the engine isn't running, it's not using ANY fuel. Duh.
Personally, I'd rather keep the motor running if I know I'll just be starting it again in a few minutes. 80% (or some such, don't remember the exact figure) or engine wear occurs at start-up. Yes, I know, cold start-up. But even on warm start-up, most of the oil is in the oil pan and it has to work it's way up through the engine after start-up.
Many manufacturers including Ford are adding start/stop systems to their cars to improve fuel economy. If these folks are adding expense to cars to simply stop the engines at traffic lights then there certainly must be a worthwhile benefit IMO.
Many manufacturers are doing this indeed. Why? It has noting to do with "benefits".
It has to do with squeezing the most miles per gallon out of an engine, thereby giving their customers a better value for their money.
It also has to do with all the leaf lickers out there who want to kill the trees they so love by removing ALL carbon dioxide from the environment. I guess they missed the class where they teach how photosynthesis works.
