Follow up:
I contacted mobil-1 oil through their website. They confirmed that mobil-1 does NOT meet the Ford B1 spec.
He tried telling me that my truck does not call for the B1 spec but that is wrong, I got the info straight from the owner's manual.
I ended up going with the valvoline full synthetic "for newer engines", which does meet the B1 spec.
Much thanks to all for your responses.
Email from Mobil-1 begins below:
Joseph,
Odd. I'm seeing Ford calling for the 946-A spec rather than 946-B1 for 2018.
https://mobiloil.com/en/product-selector?Year=2018&Make=Rm9yZA%3D%3D&Model=Ri0xNTA%3D&Engine=S2luZyBSYW5jaCA2LUN5bCAzLjUgKEcpIChHQVMp
It's interesting, because the only 2019 Ford we've received so far is the Mustang, and I see that both the Ecoboost and the V8 Mustangs have gone to B1 specs for 2019, while both used A specs for 2018. It makes me wonder if this is a new generation of specs across the board, and we'll be busy applying for the new approvals. For the moment, though, if your manual specifically says 946-B1, I would err on the side of caution, rather than do anything which might put a warranty at risk.
Thank you for choosing Mobil,
Jim
Mobil Help Desk Team Lead