Pretty sure that is just the old synth/semi-synth v mineral arguement.
I got reamed on here for using the penrite hyper. I went thru a liter of penrite on the fist 4 tanks using 2t. Using shell advance atm.(got a great deal )
Apparently the synth doesnt mix with diesel.
I wanted to do the test and mix some up in a glass jar to see, but never got around to it. Maybe you can do this daz, and post results/pics since you've got some handy and seem to be into it atm?
For the record, I liked the penrite, and reckon the ute went well on it, but the performance, did seem a little up and down, at the time i put this down to the oil not mixing properly, but now after reading that^^ maybe it was just coughing up bong oysters?
I will have that test done with pics within a week, great idea mate.
How old was your ute? Do you know if it had ever had oil in before you added some?