Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
I have read what you wrote with some attention.
When you lubricated the running belt, did you do so with silicone lubricant especially meant for a running belt?
If so, good. But, did you also adjust the tension of the running belt?
(It should be adjusted so as to be just a little tighter than loose enough that it slips when you run on it... so adjusting it properly is a matter of a little tighter (than too loose), try it again, a little tighter, try it again, and so forth until it ceases to slip.)
Is the treadmill in question still within warranty?
Note: the squeaking, if it is not the belt itself, and if it is not caused by the belt being adjusted too tight (so if it might be, adjust the belt looser, then use it awhile and see if the squeaking is significantly lessened)... then you might be able to use normal lubricant on the 'springs'... provided that they do not shed oil or grease-based lubricant onto the belt's edges, which will rapidly fray and rot away if grease or oil gets on the belt's edges.
Let me know what you think of this, in Reply To Expert, and I will instruct you further.
Adjusting the belt is occasionally necessary. Despite lubrication, belts sometimes shrink up with age. In which case, occasional loosening is needed.
There's a hex adjustment key that comes with the treadmill. It generally fits into a hole near the part of the treadmill that you face away from while you are on it. You turn it in that hole, to adjust the tension of the running belt. (Your model may differ, of course.)
As for lubricating those springs... springs will squeak, if you're using the treadmill heavily, and/or if you're a well-built bodily type.
If those springs are well-separated from the running belt, not adjacent to it either as the belt passes on the upper side, nor adjacent to it as the belt passes on or near the lower side of the running platform, then lubricating them might be the first thing to try. A grease lubricant for moderately heavy machinery, applied to the upper part of the springs, might help - provided that there also is no rubber gasketing nearby in this model, otherwise the grease might get on the rubber gasketing and decay it.
Does this answer your question adequately and completely?
OK. Would you prefer that I cede this case, in favor of an Expert here with specific experience in dealing with your specific model?
That can be done, and it will involve no additional expense if you receive advice from a second Expert on this question (or a third, fourth, etc... in theory at least. I'm not in charge of pricing or charges in the least, so I am not absolutely sure of this. But a second opinion has never cost a customer anything extra in my experience, which is 7 years long with JustAnswer.)
OK. I have Opted Out, opening the case to an Expert with specific experience in the Nordic Track 1250.