[COcyclist]

The PD TDI has 3 extra glow plugs in the coolant at the top of the engine. This was done by VW to speed warmup and give some heat for defrost and cabin heating during cold starts in winter. There is a large current draw on the alternator until the engine reaches 150 degrees F when the computer shuts them off. This is yet another reason why your TDI gets poorer mpg when it is cold. For optimum mpg you want to do everything you can to help it reach full temperature as soon as possible.

What to do? Here is a partial list:

Park in a heated or insulated garage.

Install a tank type coolant heater. Google FrostHeater on TDIclub. This allows me to plug in a couple of hours before I drive and puts heat in the head for easier starts, and coolant so defrost works better. I highly recommend this mod. I use before I drive even in summer. It really helps the poor engine start better if you have to park outside at 20 below zero like I did this last winter.

Put a small electric space heater in the cabin for a few minutes in winter. I have one with a tip over protection that I put on the driver's side floor. 15 minutes takes the chill off the entire cabin. You can allow the engine to fully warm before calling for cabin heat from the engine.

Grill blocking. I use black foam to block the upper grill year round and put a hard cover over that in winter (partly to protect from rock chips).

Katz stick-on electric heater on the oil pan. This warms the oil and the bottom of the engine. Surprisingly, this heats the whole engine compartment more than the tank heater.

Make sure your noise panel is in place and intact. The VW comes with a partial "belly pan" under the engine. It is molded plastic and easily damaged or sometimes mechanics remove it for engine service and it is not replaced. This allows lots of cold air into the engine compartment and hurts aerodynamics. I have installed a Panzer Plate made from 1/4" aluminum and still have the noise panel next to the engine. It took a little trimming but I feel it insulates better than just the aluminum.

I may add more if I think of something.

I almost forgot. In addition to all of the above, do a few pulls with boost to get some combustion heat into the engine and coolant loop. This is one time where it makes sense to do some medium hard accelerations to get to 150 degrees and get better mpg.