2008 Toyota RAV4 2.4 liter lacking mpg

Hey Eric, I got a 2008 Toyota rav4 they said it would void the warranty if any other plug other than the Iridium plug was used, but being that warranty has long since expired. I was wondering if any other plug would help my mileage, got a recall on it stating the oil scrubber ring would fail at 150,000 & it would start consuming oil, I rebuilt the engine @184,000 miles as it had started consuming oil. I guess changing the oil @ 3500 instead of the 7000 the owner’s manual recommended was a good thing (got a brother whose a product design engineer he said always divide the maintenance schedule in 1/2) but I replaced all the rings with standard rings. Compression is well within the tolerances, but lacking mpg was higher before, 31 mpg now it’s only 22 mpg, wondering if those E3 plugs might be just what the doctor ordered?