Oil + additive viscosity

I checed the oil guage and it reads accurate to about 3 pounds. I used my air compressor to check its accuracy. Another thing. I would like to mention is here at oz the sump capacity is somewhat different. I was filling it up at almost 5 quarts where the fill capacity here is actually 4 quarts ( no filter) so I will lessen this a little to see if it makes a difference also.
Regards
Billy D...
Could be a different pan, but are you on Imperial quarts? Imperial measure is larger.