My dad has a 03 Tundra v6 4x4 (access cab). I borrowed it yesterday and noticed it seemed to have very low oil pressure. I'm not positive, but I think it's got somewhere around 100k miles. When at idle, the oil pressure will drop below the first line (1/4 up). Once you get going it'll raise up to about the half way mark. Is this typical, or should we be concerned?