Why must the 2004 Cadillac cts use only synthetic oil as mandated by GM4718M? I can’t find an answer to this question.

I have an oil consumption issue 1 qt now every 5-6000 miles. I can’t find an answer to this question.

Thanks in advance

 

Acceptable oil consumption. GM4718M is a spec. What it means to you is: If you cut costs and don't use Mobil 1 and engine has a mechanical failure including stuck rings and it is determined by sluge or oil sample. Your on your own, no warranty this will also include most extended warranties. Oil life computer will not know and over shoot oil change by 2k or more miles. Average Mobile 1 oil change interval should be in excess of 7500 miles.

 

I know GM4718M is a spec. Why must the Cadillac meet this spec? The vehicle has 85467 miles. I know GM (dealer)says the is oil consumption is acceptable. I’m just wondering why the Cadillac must meet this spec. What’s the technical reason? What is this based on? No oil cooler, corvette engine? I purchased the vehicle used at the time of purchase the vehicle had 45967 miles. I don’t know what the previous owner used conventional or synthetic. A Cadillac dealer suggested that I try conventional oil and see if this helped the oil consumption issue.(yes thats true) Since I purchased I have used Mobile 1. I know Vavoline full synthetic meets GM4718M I may try that at the next change to see if this helps. I don’t think 1qt is acceptable period.

Thanks in advance