Why would you not use synthetic oil?

[Greenbeast6.9]

I have ran WMO before in my truck for about 6 months and I am getting ready for a trip, why do I see not to run synthetic oil? I have a large supply of used schaeffers oil at my shop, also I have syn trans fluid. Can anybody give me a reason that you do not run it?

 

[argve]

Pour it in and enjoy... The Goat Truck didn't even notice a difference between the taste of man made oil and dead dinos.... Will work out just fine...

 

[Greenbeast6.9]

Thats what I wanted to hear! I have my filter bags showing up today and I am moving down here to TN this weekend with a 24ft enclosed and 900 miles round trip!

 

[04_6.0]

I have never noticed a difference when running it in mine either.