The thing that puzzles me is it runs well once it is running, and at the temperatures you say you are starting it in, the glow plugs shouldn't be that critical. I had a customer who was not having trouble starting the tractor, but it started very rough and smoked a bit after it started, and would gag you out of the garage. I solved his problem by convincing him to quit using the off road diesel he was getting on the Indian reservation. He said he had always run it in his Kubota with no problems, but I proved to him that his Mahindra 2015 didn't like it.