Hi Jymbee,
As you may be able to tell, we live in the Niagara/Monroe/Orleans County area of NYS.
We have had a 2001 Ford F-350 with the 7.3 diesel since '03, and our 2011 Kubota
B2320 from day one, and never use any block or other heaters without having any cold starting problems. We run the recommended 5W-40 full synthetic oil in both, and use street diesel with Optilube like DeereMan and Raw Dodge suggested, allow the glow plugs plenty of time to prewarm and then go low but don't sit at idle to warm them up.
We do leave them running once started, unless they will be sitting at idle for more than 10-15 minutes, (this is true all year round) to avoid unnecessary restarts and still conserve fuel.
I used to use PowerService White in all diesel we purchase year-round, but after reading analysis of the lubricating properies of various diesel additives (which has nothing to do with their antigel/anticlouding ability) we changed to the Optilube, and it has also worked well.
For our multipe gas engines (cars, gennie, smaller mowers, and chainsaw) we use Stabil or a Stabil clone designed to reduce the ethanol induced water absorption and varnish formation from evaporation, with good effect.
For our usual temperature ranges, we have never had any trouble starting (except for some slowing of the process in our little Hondas- Japanese cars are never happy below 20 degrees F in put experience), even when the radios and other LCD displays are very sluggish 2nd to the cold.
Our Kubota has spent all its 2+ years in an unheated temporary garage or pole barn. The first year plus, it was in a Shelter Logic tent garage, then last wintwr, it was in our unsealed, and unheated pole barn withvthe wind blowing at it from under the garage door (it only closes to about within 6" of the gravel floor, pending pouring of a concrete floor-next week!) and still started first time every time.
I did invest in a charging system meter that plugs into the power port/cigarette lighter and last year when it showed that the Ford truck's two BIG batteries weren't holding their charge up to par, we pre-emptively changed them out for Wally World batteries, with a great improvement in cold cranking from the year before.
I check the power/charging systems of all the vehicles with it in late fall, under cold weather conditions (under 32F) and address any deficiencies it reveals preemptively before the real cold hits.
We only started the diesels a couple of times per week in the winter, as the truck is only really used to plow, and the tractor is mostly used for moving firewood, with a little supplemental snow removal as needed, and they still started easily each time.
PM me, if you need any more/other local area info.
What area are you in generally?
Thomas