Doesn't the little button turn it off?

Why bother? We are talking0.000025 mpg..............MAYBE.

Yes the only real way to have a MPG increace is if are very anal retentive and track every purchase of fuel over long periods like a year or more. Average person can not track a 1 mpg increase or decreace.

I would think a good way to increase mileage would be to install locking hubs on the front, if it's even possible. Just pondering.

Yes the only real way to have a MPG increace is if are very anal retentive and track every purchase of fuel over long periods like a year or more. Average person can not track a 1 mpg increase or decreace.

If you can't track it, is it there? I do feel mine cutting on and off in the floor position when sitting at a light idling.

I don't have a clue what I'm talking about here, but just say the thing burned 1 gallon more fuel per tank, which no way it does, but just say. So that is like 5%. So 5% of 24 MPG is 1.2 mpg...... 1.2 mpg decrease because the thing is cycling on and off. And remember it ain't using 1 gallon so it is less than that.

The A/C also runs in the floor position.

Just love how a little cold weather brings out the "if I do this, I can squeeze the N'th degree out of my fuel" crowd. If you want to improve your fuel economy, move someplace warm.

Let me clue you in on fuel economy, especially with electronic controlled, charged-air cooled diesels. Cold weather will kill your economy. Diesels don't like to burn cold diesel fuel or suck sub-zero cold air. These engines already tend to run on the cold side for a diesel and won't be helped much by overchilled charged-air. Only a hunch with the computer logic but the computer may be keeping the EGR open longer in extreme cold weather to rewarm the intake air (remember that clogged MAP sensor in the intake manifold?). An open EGR valve will have a dramatic negative impact on fuel economy.

BTW, my last two tanks of fuel only got me @ 20 mpg running expressway miles in -5F to 5F degree weather, mileage that I would consider poor by CRD standards (ie, burning 20% more fuel). Rather than disconnecting your A/C, you would likely do better to use your block heater to cut your warm-up consumption.

Actually, in the very cold ambients the EGR is actually shut off until the engine is completely warm. This is due to condensates which will form in the EGR pipes after the cooler and then clog the intake. Also, more EGR will increase the fuel economy and allow the engine to burn cleaner (cuts down NOx formation). There are corrections in the SW to adjust the fuel quantities based on ambients, EGR %, etc. etc. A lot of fuel mileage decrease is due to the winter blended fuel.

Additionally, the A/C compressor draws about 15-30 N-m of torque depending on temp and head pressure. The ECU adjusts the fueling through a PT1 filter (software) such that you hardly feel the AC kick on/off. In the emissions test chamber it's about 1.3-2.0 L/100km difference in economy with the A/C on (worse economy, of course) - so turning it off if you don't need it is a good thing. If you don't want it on, unplug the connector from the compessor.