There are only two "tricks" that should help at all: (1) make sure you have a working thermostat and (2) NEVER take a trip shorter than 30 minutes at highway speed.

If your engine does not warm up such that the temp guage is right at the first tick left of dead center within a few miles at highway speed, regardless of whether your block off the radiator, then your thermostat has died -- they are designed to fail OPEN.

Further, until the engine is fully warmed up, the viscous fluid heater is working (and sucking up fuel like a sponge) to warm the engine. Short trips will have it working ALL the time, and your mileage will drop like a rock. If the thermostat is not up to snuff, you wind up with the viscous heater working ALL the time, and that will really kill your mileage.

I've now put 145,000 miles on my 2005 CRD. Here in Virginia, overnight lows sometimes drop as low as -10˚F, but usually are in the low 20s. I have had occasion to drive it at -10, and have NEVER blocked off the radiator. Since my driveway empties onto US 460, I have about 5 miles at highway speeds before hitting any slowdowns, and my engine is easily fully warmed up within that 5 miles. Since it will not warm up at idle, if you have only city street speeds, it will take you longer to warm up under those conditions.

Winter diesel fuel is about 10% less energetic, so you will get 10% lower mileage in winter than summer, and there is nothing you can do about that. I've been getting about 24 mpg overall, and about 29 on road trips where the entire tank is AFTER it is fully warm. This compares to about 26 overall and about 34 on summer diesel.

Haha so my first morning with the temperature in the teens and my Libby fire up for about 5 seconds and died. I tried to get it started for awhile and it never started. I didn't have it plugged in, didn't think it was that necessary. Lol any clues would be helpful?

Haha so my first morning with the temperature in the teens and my Libby fire up for about 5 seconds and died. I tried to get it started for awhile and it never started. I didn't have it plugged in, didn't think it was that necessary. Lol any clues would be helpful?

Haha so my first morning with the temperature in the teens and my Libby fire up for about 5 seconds and died. I tried to get it started for awhile and it never started. I didn't have it plugged in, didn't think it was that necessary. Lol any clues would be helpful?

Also tire pressure is 40 should i lower?

No, the higher the pressure the better your mileage will be, if you can tolerate the rougher ride. Inflating to the sidewall maximum will give the best mileage and load capacity; radial tires do not bulge in the tread and will not appreciably wear in the centers with higher inflation.

I use a 215/85/16 tire inflated to 45 psi. It's harsh, but they are wearing well after 2 rotations and 40k miles. Of course the sidewall max is upwards of 100psi, FWIW.

The nasty old OEM Goodyears probably do bulge the centers with maximum inflation, but those should be placed into the landfill at your earliest opportunity.

The GDE TCM would help you lockup at lower speeds and boost mileage. Not sure I'm onboard with folding mirrors on long trips, I use my mirrors all the time on the highway.

I can't keep it below 2000 rpm, pretty much any time I'm on a 65 mph highway I'll drive 73-74 mph, that's around 2,300 rpm. Even so, I get 28-29 mpg on long highway trips.

Most of my driving is at 70, which is just a hair over 2k. I came very close to getting a GDE TCM but since 90% of my driving is highway, I started upgrading the audio.

Wind noise is a lot better with the mirrors in, it takes a while getting used to it. But I never trust them anyways and turn my head and look.

Well I just got my CRD and was excited to see what my mileage would be. So far in town I'm only getting like 18.5mpg. And when I say in town I mean driving like 8 miles to work or 15 miles to the nearest Walmart.