Quote:
Originally Posted by yossarian19
I'd love to see some honest to god before & after on mpg; I'd be surprised if it was as much as 1.5 mpg. I don't know how much work the PS does compared to the AC but I only lose 1 mpg or so with the AC on. Still, 1.5 mpg for a low-buck mod would be sweet.
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My intuition on this is there is no way you would get 1.5mpg savings on a Jeep. As 2000mc pointed out, the mpg savings is relative to how efficient a vehicle is in the first place, and the size of pump. As was pointed out, you'll likely get about 0.5 mpg better.
If you currently get 20mpg, then 1.5 mpg savings represents an 8% increase in fuel economy, which doesn't seem realistic. However, a 1.5mpg improvement on a car that already gets 50mpg seems realistic, since it represents a smaller % increase in economy (3%).
All of this just points out the superior nature of calculating efficiency by using L/Km rather than MPG. There is also less room for deception when marketing a product that saves x amount of L/km than marketing it to save x amount of mpg. Sure, I could save 10mpg by using Acme's fuel saving Widget; if I already drive a 1000 mpg car.