Our 2011 JK was burning over a quart in less than 1,000 miles when running 5w-20 as is recommended in the manual. Switched to 5w-30 two months ago and haven't lost a drop since. I was told they only switched to 5w-20 to try and squeeze another 1-2 mpg out of the 3.8l engine, and it had run fine for years on 5w-30. No problems so far and it's an easy fix.
Welcome to the forum, I am glad you now burn less oil. I am curious, did you change brand of oil? synthetic/conventional? any other factors?
(the following is not aimed at motechsc or anyone in particular)
Also, the CAFE standards aren't per vehicle. They are a formula averaged over all the entire fleet of vehicles sold. Although, the definition changed last year to account for vehicle "footprint", it's still an average over thousands and thousands of vehicles. (as are EPA estimates, etc.)
So any difference in fuel economy in an individual's experience is more likely due to other factors than changing oil weight.
I have a very hard time believing that simply changing the weight from 5w-20 to 5w-30 makes an absolute difference, especially regarding oil consumption.
I don't buy it for a number of reasons.
First, viscosity grades are not absolute values, they are ranges. At operating temp, one brand's xw-20 may actually be "thicker" than another brand's xw-30.
Second, conventional verses synthetic: some synthetics pass the tests for multi-weight oil even though they are actually single-weight.
Third, additive packs and viscosity improvers. They vary wildly in quality and effectiveness between brands and even between formulations within a brand. Many synthetics have no need for VIs and therefore have a higher concentration of detergents, etc in their pack.
Fourth, changing from 5w20 to 5w30? why no oil consumption while still warming up to operating temp? They are both rated 5 when you cold-start. it takes a while to get up to operating temp. Did the engine only burn oil when it was hot?
It's all way more complex then I am making it seem. So just stating an oil viscosity rating is simply not giving enough information. Brand, formulation, and synthetic or conventional are all just as important to know about as viscosity rating.