Interesting thought. When I'm freeway riding, and come off the gas - usually due to traffic and whatnot, you can distinctly tell the car progress is more coast-ish without getting pulled down by natural engine drag. It is definitely a little suspended as compared to less complex vehicles. I can tell because my wife freaks out in the passenger seat because she "can't feel the car let up". I don't really care either way personally but I do notice it.

 

I don't know what you are coming from but the GS is a unique driving car. When I first got it, it took me some time to get used to it's drive and behavior. Honestly I think it's good that it will maintain speed when coasting and I don't see this as an issue. Mine does the same.

If you are really worried, you can remove the negative on the battery and leave it unplugged for a while. This will reset a lot of the "learned" behavior. This also improved my MPGs drastically from avg 16mpg to now avg 20mpg with a mix of city and highway driving, more city.

 

This is a great thing... just learn to anticipate light changes and let off the gas earlier and coast to stop..

If you prefer the car slow itself quicker, let some air out of the tires.

 

I have a 2015 , and I see the same thing. Compared to all other cars i have driven, engine braking is very light to minimal on the GS350. I took a long distance trip this weekend and noticed on I-5 i can get the car to register 30mpg @ 90+ on somewhat flat ground. Even when experimenting with lifting completely off the throttle and coasting from 70+ to an off ramp a 1/4 mile away where the exit speed is listed at 40, i cannot get the car to engine brake enough to not have to use the brakes. COnsider it a feature and not a bug.

P.S. my 2105 gs350 f sport has about 27k miles, l-certified, new OEM tires on front and OEM tires on rear with 6k miles on them.

 

Also, reducing throttle abruptly, aka taking your foot off the gas suddenly, causes an increase in oxides of nitrogen NOx. I remember owners complaining of that when they started computerizing the fuel injecting cars at the start of the transition away from carbs. That's probably one reason the throttle doesn't immediately drop like it will on my old cars.

 

+1 on the first idea, it's a technique I've been trying to figure out on the GS. I had it down with my G35 where engine braking on the A/T was very noticeable.
I doubt I'll be trying out your second idea...

 

I'm beginning to think the minimized deceleration is intended, it would clearly result in a smoother ride and much less neck-snapping with even aggressive drivers (unless they're the brake-or-gas type).

 

Purely for the unnecessary and to screw with tailgaters behind me - I've adopted paddle downshifting instead of coast-engine braking (which we all agree, the GS doesn't have in its genetics). No matter what mode it's in, dropping a gear or two on the paddle invokes a pretty good feeling of drag.

 

I have worded more precisely:

I have 2015 with the new 8 speed auto too.

This 4GS has been deliberately designed with WOT - sudden throttle lift-off - gear hold and concomitant engine braking - not just on Sports Mode, but even on Normal and Eco Modes!

This feature is more prominent in Sports Mode, as opposed to Normal and Eco Modes.
This feature is also much more prominent the wider throttle opening, and the more suddenly the throttle lift-off.

My old 3GS, when Power Mode was selected, WOT with sudden throttle lift-off would automatically activate gear hold for engine braking, but not as prominently holding gears for engine braking as the newer 4GS.


To the OP too. Sorry, I totally misread your opening post.
I thought you were wondering why your car was decelerating too much, when you are in fact wondering why it is not decelerating enough on coasting.

Not decelerating much on coasting is a sign of great efficiency, with respect to lower mechanical friction, less tire friction, lower wind resistance - and possibly the use of a bigger heavier vehicle, with heavier flywheel or heavier alloy wheels/moving parts like bigger heavier wheels/tires which stores more kinetic energy for longer coasting...
.

 

Wow! That's news to me! That automatic downshift on throttle lift operation sure doesn't seem to correlate with obtaining increased fuel mileage. It makes me even more glad that I have the 6-speed transmission...

 

Re-worded.
Just out of interest, does the original 4GS of 2013 with 6 speed auto have any degree of WOT with sudden throttle lift-off accompanied by holding gear and engine braking?

In terms of the new 8 speed auto having increased fuel mileage?
On standing starts, it is okay to full throttle, but on rolling starts and full throttle, the new 8 speed auto seems to be very reluctant to kick down, or more in particular, it is reluctant to kick down to a low enough gear to rocket off.

On rolling starts or in particular, on kickdown with full throttle, the auto tranny response is very unpredictable - sometimes it will select the perfect gear for a perfect rocketship acceleration, but other times, it will not kick down to a low enough gear resulting in sluggish acceleration in the wrong gear.

I guess the reluctance to kick down to a low enough gear helps with the fuel economy, at the expense of rapid acceleration.
.

 

I was all about the 8 speed originally. Every pro review knocked the 6 speed for being yesteryear technology, so the 13 was off my list. We don't get many AWDs out here in the desert, so all I got to drive were the 8 speeds. One day, a beautiful lux package showed up that was the absolute cleanest GS I had seen in the color combo I loved. It was a 13, so I reluctantly drove it. The first thing I noticed is how predictable and fast the shifting was. Never looked back. The 6 speed more than makes up for any missing options in the 13 model.

 

More gears are used to make up for a lack of torque. I don't think the 3.5l is lacking that much, a low first and a couple of overdrives get it done. More gears just makes a heavier, longer transmission.

For the ones that see sudden lift / immediate engine braking, this is in ECO mode? My 13 can be made to do that in Sport or Sport+ mode. It holds a gear a bit longer, delays shifts and when I let off it will not upshift unless I do it manually or move to normal / Eco mode.

 

No. If you mean traveling along normally and lifting off the throttle - there is no automatic downshift with the 6-speed transmission. However, if you are in Sport mode and have lifted from being WOT where the transmission downshifted to a lower gear - then this lower gear is purposely held for a lengthy period of time on the premise that you will want to remain in that lower gear when you get back on the throttle again.

Personally, I do not think I would like my automatic transmission to automatically downshift when lifting from the throttle. That just seems weird to me.

 

Another experiment they could try is to reach a given speed and let off the gas to see how far and how fast you coast. Then repeat and instead of just letting off the gas, knock the shifter into neutral and note the results. If you coast farther in gear, it is obviously still producing power. If you coast farther in neutral, it is just your perception that it is not engine braking at least a little.