might be wrong, but if you're rev-matching properly, engine braking puts little stress on the clutch. now, if you're not blipping the throttle enough you can have a good amount of clutch slip when you re-engage the drive train and doing that often may lower the life of the plate. i've always thought that if you're doing it right, the only disadvantage of downshifting to slow the car is lower gas milage since the engine is at higher revs. but, on the other hand, it reduces your use of the brakes so your pads may last longer. trade off....

 

Modern engines usually don't use much fuel, if any, when engine braking with the foot off the accelerator.

I think the disadvantage is a bit of extra engine wear.

 

Engine braking doesn't put any more stress, in fact, I doubt it puts anywhere near the stress that normal acceleration does on the clutch and drive train. As Crassus said, if you don't rev match cleanly, you'll put a little added wear and tear on the clutch disk but unless you're consistantly sloppy about it, I don't think it'll be significant.

As for any impact on fuel consumption, I think it would be negligable. Maybe someone can confirm this but I've heard, and get the impression with my car, that the ECU shuts off fuel flow when you're decelerating with your foot completely off the gas. My reason for saying that, and I could be wrong, is that my car decelerates nicely with my foot off the gas down to about 1200 rpm. It then "kicks back on" (?) to establish an idle. In the lower gears, the effect is pretty abrupt.

FWIW!
Drive Safe,
Steve R.

 

For normal crusing at general traffic flow speeds, I suggest upshifting at around 4000-4500rpm. This is generally the area where the exhaust note changes to be a bit droney.

I also find that 3rd gear around 4000rpm is the approximate speed limit in a lot of areas around me. If I stay in 3rd I can hear when I'm speeding by the exhaust note, in higher gears my speed tends to creep up without me noticing.

When travelling in stop/start traffic at really slow speeds (ie 5pmh) don't try to creep along in 1st gear, use the clutch to disengage/engage when needed.

Don't try to do burnouts- the diff can be fragile.

 

I shift to 5th in 35... Maybe this is because I got used to the 350Z first