California is about to change fuel standards. That means higher gas prices. But how high?

In a vote scheduled for Friday, the California Air Resources Board is expected to set stricter carbon intensity targets across the state for transportation fuels, including gasoline. If approved, the move is expected to increase prices at the pump — but how much has become a matter of increasingly fierce debate.

Some point to projections of prices rising as much as 47 cents per gallon next year. Others warn — with plenty of caveats — that prices in 2025 could climb 65 cents, while Air...