typical of this engine's oil gauge. Mine hardly ever goes past the first third, and if you check with others, it's pretty much the same for most of us. It's a known weakness. Best way to find out is to connect a standard mechanical gauge using a T off the sending unit tap under the oil filter. It's a metric fitting, BTW. 10mm IIRC. Haven't done it yet on mine. If the oil gauge is flaky you probably won't notice much of a difference when changing to 15W40, but do it anyway, especially if it's hot and you rrun the engine hard (=sustained high speed driving).
