Engine vibrating/rumbling over 90km/h

[Iceblade]

Hello, was wondering if you guys can help diagnose my problem. I will be bringing my vehicle into a honda dealership tomorrow to get it looked at, in the meantime I was wondering what may be the issue with my engine.

Some background:
2008 Civic Si FG2
Temp outside: approx -25C the past couple of days, I have 5w-30 synth used about 3000 km, total odo is ~38,000km. Using Mich. X-ice been used for approx 3 winter seasons, recently put on at the beginning of nov, had no issues until now.

Symptoms: while driving 90km/h-100km/h, the engine vibrates and rumbles very noticably, making the entire car shake (and bringing out all the rattles in the car - but that is a different story). Approximately around the same time, the CEL came on. Driving anything lower, the shaking does not occur, or is unnoticable. Does not shake when the car is at idle or warming up.

I haven't had a chance to check the oil level, but will get to it after work today. I'm thinking it may be related to the extreme cold that Edmonton recently experienced, something may have cracked. I park outside, and as the first night of our -25C, the vehicle was not plugged in (block heater), but the vehicle still fired up, I have been recently plugging in my vehicle. Anything else you guys can think of that may have happened?

[thunderdome]

can u go somewhere such as "autozone" or "pep boys" where u can get ur car scanned for free which will give you the CEL code??? i'm not sure what stores you guys have up there where this can be done but that would help us out a little better ...