Not getting 99.9 when coasting under 15 mph

[stevenalice]

My commute is 15 miles, of which the first few miles and last few miles are on surface streets and the bulk on a highway going 55-60 mph. Both for the drive to work and the drive home, the last mile of my commute is a slow drive through an office campus parking lot (yeah, I live in Si Valley).

During this last stretch, I accelerate to roughly 20 mph then take my foot off the gas to coast. Since the car is warmed up, I always get green arrows and 99.9 mpg. Often I'm able to feather and get true coasting, no arrows and still 99.9.

However, 3 days ago I noticed that after I take my foot off the gas, I start at 99.9, but the mpg drops fast as I slow down, so when I reach 12 mph it's about 40 mpg (though my foot's still off the gas). When I try to feather I can't get that sweet spot between orange arrows and green arrows, and the mpg wavers around wildly. It seems just like when I first start the car. What gives?

Yeah, it's just 1 mile of my commute, it wouldn't affet my total mileage much. But I noticed the same thing yesterday, when instead of going home I went to a meeting, and after 20 miles of freeway driving I had to slow for rush hour traffic, and I had low 40s mpg when driving at slow speeds (8-15 mph). It's as if the gas engine isn't shutting off at slow speeds anymore.

The only thing I can think of is that the weather is finally fall-ish here in the Bay Area, and instead of being around 75-80 degrees during my evening commute, it's now about 65. But the air temperature during my morning commute has been the same for the past month or so, around 60 degrees. BTW, I don't run heater or AC. Any ideas as to what's happening?

[mikepaul]

Don't set your climate control higher than 70. I notice it blows unheated (if not cooled) air in the mornings lately at 70, while at 71 it blows heated air, which requires the ICE to run more often.

I never noticed this 70-degree thing before, but given that the outside temp was 55 the difference between blowing heated and unheated air was noticeable...

[kDB]

i noticed this too. usually happens to me after about 30 minutes of driving on highways. i will then exit the highway and want to EV/Coast the rest of the way to my house seeing as it's less than 1/2 mile from the highway. but no matter what i do the car will not shut the gas engine off. i'm always at one bar short of green also. a/c off.
well, it looks like i finally have enough to blow on an EV switch, so i won't have this happen much longer.

[Frank Hudon]

your probably not getting into S4. I've noticed this with the wife's 2k4 in the last few weekends, that's when I get to use that car some of the time. I've noticed it with my Classic and the MiniScanner has shown that the ICE is still trying to get to 70C on my commute home. It takes an additional 1/2 mile (approx) to get into S4 where the ICE shuts down. OAT about 55F in the afternoon. Mornings don't count as I use the block heater to have the ICE temp about 115F-47C.

[Jaguar88]

check your tire pressure

[afternoonnap]

I have noticed the same thing recently, which does coincide with cooler weather. At the end of my 1/2 hour commute, the ICE won't turn off unless I come to a full stop for several seconds. Once off, it subsequently seems to shut off more easily, as it always used to. This happens even if the battery is well charged, and if all climate control is turned off.

It seems as if it thinks the ICE isn't warm yet, but after 20 minutes of highway driving I would think it should be.

[hdrygas]

I have noticed similar behavior in my Prius. Happened just today on a portion of my regular commute where I can always glide and I could not get it to go in no matter what I did. I have had this happen in other "known glide areas" The car was warmed up (ScanGage 170F) and the heat not on nor the air. The best I can do in this situation is 99.9 with engine on and charging intermittent. 4-6 bars on the battery. Have not figured it out, but there is more to this programing than is apparent.