The oil not darkening is IMO a testament to it's ability to withstand the distance in an otherwise reasonably clean engine. I too will attest to that.
Use an A1 30 weight and see how quickly it darkens...it's not cleaning per se...it's simply becoming used up/worn out quicker.
Use an A1 30 weight and see how quickly it darkens...it's not cleaning per se...it's simply becoming used up/worn out quicker.