Today I thought I would do an experiment. I haven't searched all our archives here to see if the topic was covered already. My FE has been dropping slowly since about 5,000 miles and I was wondering if the upcoming oil change will start to increase it again. I used to get some low 50-mpg days on my drives but find it hard to get over 45-mpg. With some very-attentive driving I was able to get 48-mpg this week so am very pleased though it took some very intense concentration for most of the day while in the early days of my car it was just normal driving and not forcing the car into the ICE-type of IMA-only speed maintenance.

Today I tried to put the car into Neutral on every downhill and any time I was braking (so the battery would not charge). Most of the day the FW was around 35 mpg and the last few hours of the day, unfortunately, improved FE to an end-of-day of 39.5 mpg. Man is it hard to actually get a LOW mpg readout sometimes. =)

I wanted to see what the shifting-to-Neutral effect has on the car. Though the i-MPG does not show anything the car IS attaining a high-mpg sometimes but it definitely does not attain as high a number as if you are in gear and coasting at zero Charge/Assist or if you are in ICE mode with some IMA assist. With normal driving (staying in D all day) my daily averages have been 49.0, 43.3, and 45.9 - not stellar but higher than 36-39 which I got while driving aroudn in Neutral.

I usually don't shift to Neutral for any reason (as I don't like being out of gear when driving) but I have seen some things in an occasional post and thought I would give it a try.

 

hm.... all I can say is... when coasting its best to do it in D with throttle control because at least the valves can seal shut and the electric motor is lightly propelling the car without injecting gas into the engine.

While in N, the engine is just fed JUST ENOUGH GAS so that it does not stall out. People perfer D because not only coasting is just as effective as in N but the power is there when you need it.

 

Yeah, you will definitely get worse FE in neutral than in D. As Phil mentioned, when coasting in drive, you will expend exactly zero fuel. While in Neutral, it's the same as idling.

 

Unless, of course, you actually shut off the engine with the key... a "forced autostop". This can be very dangerous (reaction time to accelerate must include turning the key back on... and possible loss of power brakes / steering). It's a possible benefit on older HCH models, but not the HCHII, since all the valves completely close and fuel is completely cut when coasting in "D" with key on.

 

In theory you could do better with FAS vs. deadbanding, the reason being that FAS takes the entire engine out of the loop while deadbanding just eliminates pumping losses but keeps the rotating assembly in motion. It's just a matter of having a little resistance vs. no resistance at all. But, personally, I wouldn't be one to bother. It's kind of a pain (but worth it to some) and I would wonder what happens to the CVT clutch when disengaging and re-engaging repeatedly at speed. Training the heck out of one's right foot sounds like a less risky expenditure of time and effort.

 

Flash, far more likely that your mpg losses are coming from our colder weather. My last few tanks (except for the forced regen one) have all been about 55 or better. This one I'll be lucky to keep it above 52

 

I actually did some FAS vs. P&G testing last week on two consecutive days,
and I actually got 2mpg better doing the P&G opposed too the FAS.

Both FAS and P&G started at 45 mph and I let it coast till 30 mph. I did both
over the same 7 mile span on empty road on way to work. With FAS I was
at 71 mpg for 7 miles and P&G I made 71 mpg at 5 miles.

I am not sure how durable the CVT would be using FAS I think it is best left
to autos with stand transmissions. I won't be doing it again stick with P&G.

 

In no way do I encourage coasting in Neutral or FAS - coming from a manual transmission for my whole life I never liked being in Neutral as you don't have any power on demand in emergency situations ... I thought I would do my own test as I had heard others mention something but also that the i-MPG gauge shows 0 bars and I was wondering why it sometimes registers 70 mpg but mostly just 0 mpg but the average mpf actually reads 38 mpg. Weird. I'll just stick with keeping the car in D as I have been for the 6.5 weeks I've owned the car (6,700 miles so far - wheeeeeee).

mmrmnhrm - Haven't we been through this before? You've driven through the Western PA area that I hit every day so we both know the terrain. I average 150 miles daily so I burn through a tank every 3-4 days. That means that weather has little effect on my FE since the temperature does not swing wide enough over 3 days to make a difference. If, however, I only drove 50 miles a day then it would take me nearly 2 weeks to burn a tank of gas and THAT would be impacted by weather going from 80F a week ago to mid-50s this week but not when the tank only lasts 2-3 days.

I too have had days of 150 miles and avg FE of 42 mpg but the last 30 miles were at enough downgrade that I could maintain ICE driving and when I got home at 180 miles the avg FE was around 48 mpg. Neat how just 30 miles of 180 miles (16%) made an increase of 6 mpg. Nice. But when you max out the mpg meter (100+ for 5-10 miles of driving) then it does make a difference. Likewise, on stellar days but some stop-and-go traffic or hills I can drop from 48 mpg to 42 mpg in the last 10 miles of the same 180-mile day. Such is life.

 

Flash, your daily driving actually makes you more susceptible to weather changes, not less. Since you fill up every 3-4 days, you'll see the effects of nice/crummy weather immediately, and a rainy day will completely trash your mpg. My bi-weekly fillups mean an all-day rain only results in a penalty of maybe 2mpg by the time the tank is finished. It'd be interesting to see if there are any other western PA folks who drive 35mi round trip daily like I do, and any central OH folks who do 150mi daily like you to see how the numbers work out. I'm thinking our cars' mpg numbers will be roughly the same by geographic location (actually, my distance driving cohort would probably be better than me), but the tank variations will be much greater on the long drivers vs. the short.