When it came time to replace ours two years ago, I could not get GY's that were younger than four or five years of the manufacture date. Checked all over the northeast. Camping World in NJ, who are great to work with had them and said they could NOT get any younger tires, and that GY still warranteed them as if made yesterday.
I was not comfortable with that. Not a fan of Michelin. Did a lot of research and ended up with Double Coin tires. Those that bash them, haven't done their research. Industry experts praised their QC at the factory and they're in service on trucks in the U.S. with tremendous respect for their performance.
Went up one load range when we bought them. I have not noticed a rougher ride, and they actually ride smoother than the GY's. They were also priced attractively. Price was NOT an issue for me, but it was a nice bonus that they were more reasonably priced than the GY's which rivered horribly.
About 8,000 on the Double Coin's with no issues.
Using two methods to calculate, we averaged 9.5 MPG on our last trip to Florida, from Long Island, with no toad. It was about a half-gallon lower a year ago when we pulled the toad.
The two methods were 1-Scan Gauge II and 2-a manual calculation of mileage based on fuel consumption at each fill up. Manual calculation was slightly lower. Consistency is tough to maintain when filling up. I stopped when the pump "clicked" off at the handle the first time, at each fill up and used that amount of fuel for the calculation.
2004 motorhome on a 2003 Ford V-10 chassis. Kept the highway speed at just about 57 MPH on the highway per the Scan Gauge II.