This is normal my light comes on at around 17 gals used
U can change the calibration with efi live
I need to do mine but I'm waiting till my lift shows up so I can run it out and see how much it will pick up
The blizzacks are good so are the nokians (that's what I have now) but the general altimax artics are the best out there better treadwear than the blizzaks
I had them on my Tahoe and my car trust me u won't need studs