Dear Sir/Madam

I have come across some various road projects, where the medium curing grade is applied with respect to weather condition (climatically condition).This MC-30 is normally applied in moderate cold regions because of its viscous properties while MC-70 is normally preferred in hot and dry regions. In our specification require the Contractor to use MC-70 for priming works as the project road is found in dry and hot climatic condition. The Contractor is asking for a permission to use MC-30 instead of MC-70.Iwent through the testing manual (AASHTO M82-75(1993) and found that most of the properties requrement, min.and max. are same except the following tests:
Kinematic viscosity at 60Centigrade(MC-30, 30min and 60max.MC-70,70min and 140max
Distilate,percentage by volume of total distillate to 360Centigrade
Residue from distillation to 360Centigrade.
Is it possible to allow the Contractor to use MC-30 instead of MC-70 as specified? OR there will be detrimental deffect! Please assist