I just bought a 2006 xA with manual transmission, and I want to squeeze the best fuel economy possible from it. I've always been taught that engine braking is a good thing because it saves the brakes, but I'm concerned about the impact on my mileage. Does anyone know if this makes a difference? Is it preferable to use engine braking, or should I be using the actual brakes in neutral?

engine braking is good on the freeway, esp going down steep grades. not sure about the MPG effect though (im sure its minimal). need to be careful if its wet or slippery out though cause if you engine brake to hard and send the RPMs up too fast, you can start skidding.

There is two different engine braking scenarios:

Slowing yourself on steep downhills. In this case using engine braking to keep the vehicle speed down and save from overusing & overheating the brakes makes good sense.

Slowing/Coming to a stop in normal driving conditions. In this case downshifting to slow the vehicle doesn't make much sense, you are using your clutch ($500+ replacement cost) and transmission($2000+ replacement cost) to save wear on your brake pads ($50replacement cost). HOWEVER when your xa is coasting and in gear with the RPMS above ~1000 the injectors shut off and you are using zero gas. So what makes the most sense is to coast down in whatever gear you are already in, using a combination of the engine braking in that gear and the actual brakes to slow you, and putting the clutch in when the RPMS get to about 1000. If you combine this with watching traffic ahead for slowing/stopping traffic so you can start coasting as soon as possible you can get the whole time you are coasting in gear "free", and use no gas.

Hopefully that made some sense, I haven't finished my coffee yet.

Improbcat: That makes perfect sense. I will start putting that into practice. Thanks!

I perfectly agree with the cost factor of what this jazz cat has to say. It is not worth it putting the stress on your transmission if you are not super experienced with this type of braking to begin with. I advise not to engine brake at all and just brake normally.

Do not be too nitpicky on the mileage with this kind of method, the gain is minimal and just not worth it. Drive normally and our cars will long life ahead.

Well, when you let up on the gas, it doesnt shut off the engine entirely, gas is still coming into the engine, but at an idle rate. For my xb, I idle at about .20gal/hour and when im traveling at 65 without the gas on, I get the same .20gal/hour.

you should really be using both when you are coming up to a stopped car or a light. just don't send your RPMs past like 4000 and you should be okay. engine braking should be a habit so i your brakes ever fail, you'd be slowing down the car and minimizing damage. as for gas mileage it has almost no effect. if you want to save gas just try to keep the car in the tallest gear possible.