Coasting cunundrum
 

I normally drive everywhere two up. Virtually every time I am out on the highway my wife is riding shotgun. Today I was out by myself and I was amazed to find how much less willing the car was to coast, out of gear. My wife is not a big woman, but the car is small and it would appear that the reduction in weight influences the inertia quite considerably.
I can only hope that the reduction of energy used going up hills balances the reduction in ability to coast!

You may find in gear coasting, especially going downhill, is better for fuel economy when there's more weight on board as the engine braking will have less effect. The car will stop using fuel as soon as you lift off the accelerator, but will sip fuel when idling, like when coasting in neutral. Try both, see what happens.

After 6 months of driving for economy, with my ScanGauge E, I have my wee car and the routes I drive pretty well sussed. I know where I can coast in gear and when I have to coast in neutral. Sometimes it needs a bit of both to extend my coasting for the maximum distance. I will even coast, in neutral, on uphill sections, where I want to reduce my speed for a hazard (bend, junction or roundabout). Sometimes coasting in gear is no advantage as the revs drop below those needed to stay in DFCO. There are a couple of bits I use regularly where I cannot decide whether in gear or neutral coasting is best (too short to measure average mpg). It is all suck it and see, but as my figures show, I am doing some bits right! Mind you, the colder onset of winter is depressing my FE figures (depressing me as well!).

Temperature might be a factor. I noticed by car's fuel economy and coasting gets a lot worse when temps drop into the 40s (F) and lower. Same fuel. Same wind conditions. Same road. Just a a coal snap. It can make a huge difference.

It is 45°F today and was a lot colder when I did my morning commute.

Grille block, plumbing pipe insulation.

Don't think that would make a lot of difference to my 2.5 mile trip and return. What I need is a sump heater, but I have no power to my garage.

Even then, the initial purchase cost and electricity costs would surely outweigh the fuel savings over such a small daily trip?

I've insulated the engine bay in a past car, along with the grill block. Both may not help much with the trip out, but will if the return trip isn't the next day. I had also rerouted the airbox snorkel from the outside to about the exhaust manifold on that car.

Stuff a piece of cardboard between the ac condenser (assuming you have one) and the radiator. You might be surprised, or not, but worth a try?