check the API rating.
MOST diesel oils carry a API 'C' rating and some kind of 'S' rating.. even if it is an older one.. like 'SL'
In a few rare occasions you will find a specialty diesel oil that carries ONLY C ratings and no S ratings ( probably didn't want to pay for the testing and certification _)... I wouldn't use a non S rated oil in a gasser.
I have no problem using a C and S rated oil in a gasser.
Does the api lable on your oil cary ANY kind of an S rating.. even an older one? if yes.. then it is fine