Many years ago i was taking a C150 accross the channel and approaching the coast we noticed the left gauge was well low
So we landed at Lydd to have a look. Some helpfull chap in the club told us he knew what the problem was. He just moved the fuel vent so it was behind the wing strutt and all was well! The vent was out in the full flow of air and was pressurisng the left tank more than normall. But as has been said it would have leveled itself when the fuel got to a certain level, but better safe than sorry
