This cost is in line with what is out there on the web for repair. If it includes the towing, you may be able to get that covered by your credit card. You should submit a claim for the charge now, and not wait. The final charge can be adjusted after your get more paperwork from the rental agency DRU.
"If it includes the towing, you may be able to get that covered by your credit card." -> That's what I assumed/hoped as the MasterRental policy says it covers the towing and loss of use. When I submitted the online claim form yesterday however, it only showed 3 options: collision, theft, or tire damage, none of which the misfueling can be classified under. I selected the tire damage anyhow and just explained the situation.
Christina H also made a good point after she glanced through the MasterCard policy:
“Due Diligence: All parties are expected to exercise due diligence to avoid or diminish any theft, loss or damage to the property insured under these programs. “Due diligence” means the performance of all vigilant activity, attentiveness, and care that would be taken by a reasonable and prudent person in the same or similar circumstances in order to guard and protect the item.”
"I think it is page 36– due diligence would mean not putting in the wrong type of fuel, so I would suspect that this gives the card insurance a reason not to cover this. "
I'm still going to try to submit all that I can and hope for the best.