25.5 mpg?

If you don't change your trip patterns or your locale, you shouldn't expect it to change. The Prius does the worst on short trips in cold weather.

Edit: An engine block heater could do wonders for you. I don't use one, but many others here do and can provide more insight

 

You are a prime candidate for an engine block heater as your avg. temps never get above 65 degrees all year and your winters are frigid. Those short trips you take never give the car enough time to get out of the start up cycle and past warm up temp (and into EV mode capability) before you nearly reach your destination.

I'd do two things right away:
#1 Take a trip to the local auto store and buy an engine block heater...starting with a base of under 30 mpg you will see a nice increase in mpg and in the winter it's value will be even more for useful for you.

#2 Take a trip to your local hardware store and pick up some pipe foam insulation and insert it in your grill area to create a grill block (I attached a couple pics of what mine looks like). This will capture any heat the engine creates and help to heat the ICE up even quicker. Your temps are never that high so you can run a full or nearly full grill block year round (hotter days you might want to remove it). You can barely tell the material is in your grill if you are worried about aesthetics and it's easy to install.

I'll also suggest to you using pulse and glide and neutral coast to raise your avg. mpg. I have a 1/4 mile stretch of winding roads (with speed bumps) to get out of my living community and pulsing up to about 25 mph and then neutral coast has dramatically helped me maximize my first 5 min warm up mpg. If you have longer stretches than me then a regular pulse and glide will suffice.

 

The engine also starts to heat up the catalytic converter, not only itself.

Try accelerating harder. You want to keep the engine running near full load whenever it is running. Just ticking over is the least efficient mode for an internal combustion engine. If most traffic passes you when leaving a stop then you need to press harder. More gas, less brake.

Inflate tires to 42/40 PSI front/rear.

Do not use "B" in normal driving. It should be used only as an alternative to riding the brakes when coming down very long downgrades.

I suspect that most MPG improvements seen after a "break in period" have more to do with breaking in the driver than the car.

What car would give better MPGs under your conditions?

 

Don't get discouraged as you have difficult driving conditions to get max mpg. With the block heater and increased mpg's due to it's use you are actually saving more money in the cost of gas than you are in electricity to run it. If you have a kilowatt guage you can calculate the cost of your EBH vs. increased mpg's in the Prius (something that is recommended to make sure it is worth it for you to run the EBH...but I'm sure it favors the mpg in the Prius in terms of energy use).

The breaking in of the vehicle in terms of increased mpg will pale in comparison to what the block heater, grill block and improved driving skills will produce for you. While it's nice for the car to get broken in it's kind of like planning on getting better at a sport simply by playing games without practicing...there's alot of mpg's to be had out there...you just have to go get them.

Pay attention to your car and when/if you can get into EV mode on your commute. While moderate acceleration is good from a dead stop if you are up to temp and can get into EV mode...light acceleration will keep you in EV mode and pulling max mpg's. Hard acceleration when up to temp will pop you out of EV mode and trigger the ICE...listen to your car.

Best of luck!

 

I agree that the short trips are likely the biggest cause of your poor results, especially if they are at highway speeds. Are you driving at or near those speeds?

This will give you other ideas. (I'm surprised no one has suggested that thread yet.)

I also agree with those who recommend a block heater. For short trips, it may be the single best thing you can do to improve fuel economy. I doubt your local auto parts store has it, at least not the Toyota heater. It's an OEM item, sold by Toyota Canada. I don't know if Alaska dealers stock it (I would think they would), but if not you can get it here. FWIW, I use mine year-round here in the mid-Atlantic.

I don't agree that accelerating faster will help significantly. If it does, the effect likely is small, and you have to be careful to avoid accelerating too fast; that will hurt fuel economy. Just be careful to accelerate fast enough that the ICE lights; battery-only acceleration unquestionably also will hurt fuel economy. Richard is correct in theory, of course, that an engine under load is more efficient than one that's not. But a few of us with added instrumentation have shown that the Prius engine is under load at a surprisingly low RPM, one that comes with the gentlest of acceleration rates. My own results with those rates are at least as good as those with faster acceleration. See this for more, especially post #45 where I discuss the gentle acceleration rates.

 

Why do you say that battery only acceleration hurts FE? Are you talking about gently accelerating from a dead stop and staying in EV mode up to speed when you say that is not good for FE or are you describing something else? Just wondering because I routinely gradually get up to speed from a dead stop using EV mode only and both my SGII and my MFD continue to raise mpg the whole way.

 

It may seem paradoxical but for maximum efficiency you should minimize using the battery (except when the only alternative is friction braking or engine braking). Energy conversions are always less than 100% efficient. If you accelerate entirely on battery, all of the energy used was converted from mechanical energy of the engine to electrical energy and back to mechanical, with losses occuring at each step.

As for optimal acceleration, I defer to JimboK and others who have instruments.

One thing: do you let the car warm up for any time before starting to drive? Don't do that, it's another MPG killer.

 

If your temps are now in the 60's/70's you should be in the 40+ mpg range. 25 is just not right. Even in midwinter and 6 mile commutes we were getting in the 40's. I did block the grills, but did not do block heating.

Don't baby it though, that will hurt mileage. Accelerate moderately--not drag racing, but fast enough to leave most behind until you clear about 40 mph. Rule of thumb is to keep the instantaneous mpg a little above half the indicated speed while accelerating. This puts you into a decent efficiency band for acceleration. This doesn't work as well when climbing steep hills but will give you a decent guideline in most situations.

Accelerating moderately will warm up the engine/cat sooner so that the ICE will shut down at other times improving economy. Also, try not to rely on climate control too much. If you use a lot of AC/heat/defog/defrost you will see a considerable mileage hit. Defogging will run the AC/heat simultaneously pulling a lot of juice and forcing the ICE to run. I've found that a blower setting of about 2 works well for keeping the ICE off. Use it as you need it, but don't over use it. Having the grill blocked in cold weather will warm up the engine (provide interior heating) sooner.

A good bit of advice is to drive as if you don't have brakes. The fewer deceleration/acceleration cycles you can do, the more efficient the vehicle will be. Time and anticipate.

Our last several tanks have been above 50 mpg, even though I've removed the grill blocking.

 

Richard has already given a concise answer, but I'll elaborate with a description of my own practice. I generally avoid using the battery as much as possible for the reason he cites: conversion losses. The only exceptions are where I think that because of very low power demand or duration, lighting the ICE might be less efficient. Examples are short drives around a parking lot or driveway, between closely spaced red lights, or to extend a glide a short distance.

 

I do agree with Richard that it seems paradoxical to use as little battery as possible because when I am in EV mode (either from a dead stop or at <40 mph) I am consuming no fuel.

I understand conversion loss occurs but unless the battery is below 3 bars there is no penalty for conversion loss because the ICE does not have to regen the battery (the brakes and go pedal in ICE take care of that).

Wouldn't it make sense to creep in EV mode out of a dead stop until you're up to speed to gain max mpg or to drive in EV mode as much as possible? My SGII shows 20-30 mpg with ICE engaged on a start from dead stop...OR...my SGII shows 0 mpg in EV mode from a dead stop. How can it be more beneficial for FE to "use fuel" to accelerate the car vs. not using fuel (given that my battery never dips below 3 bars at any time and forces the ICE to regen it for me)?

I'm not disagreeing with you, just don't understand why using fuel to accelerate the car is better than not using fuel in regards to FE.

 

I also wonder if the engine may not be running at the most efficient state when accelerating from dead stop? And if so then the loss may be comparable to the conversion loss?

 

All the car's energy ultimately comes from the ICE. Yes, you use no fuel when in EV mode. But to replenish that charge requires the ICE, and with the replenishment come losses as ICE energy is converted first to electrical energy, then to stored chemical energy (in the battery). Then the process reverses itself later to use that energy. Regeneration seemingly charges the battery for "free" but the ICE had to be used to get the car up to speed before the opportunity for regen ever arose.

So I generally try to avoid the battery completely. I accelerate to avoid pulling from the battery (and inefficiently high RPM). And whenever possible I decelerate to avoid regeneration and instead let the available kinetic energy (which also is not "free" though it's moreso than EV) carry the car as far as possible by gliding.

 

Perhaps this is over my head from a physics point of view...based on your avg. mpg and past results I'll take your word for it. But, it doesn't make sense to me.

I understand all of the battery energy in the car comes from ICE or braking (it all has to come from there)...understood.

I understand there is energy conversion loss when capturing and expending the energy (going from EV to ICE to EV)...understood.

However, despite energy conversion loss there is no penalty for using the battery exclusively when the captured energy (either from ICE or braking) is gained with no extra effort from the ICE on start up or use to recharge the battery. As long as I'm above 2 bars or not at full battery capacity, there is no penalty for using EV exclusively.

Please analyze this example for me and tell me how you would approach it:

On a 1 mile stretch of flat road with no other cars on the road I am at a dead stop. I accelerate in EV mode lightly until reaching 40 mph where I keep it in EV mode for the remainder of the 1 mile stretch.

Are you telling me that instead of using no fuel in EV mode I should engage the ICE during this 1 mile stretch and that would equate to better FE?

Follow up: I know you're going to tell me that eventually after I complete my 1 mile stretch in EV mode and use (for this example) 2 bars of battery that the ICE will have to recharge the battery at some point. But, let's say the next 1 mile of stretch is a gentle incline and the ICE engages and recharges the battery anyway. How can you say that I should have used ICE and fuel over the first mile instead of EV when I would be using ICE anyway on the second mile and recharging the battery (and we drive in EV to ICE to EV for miles and miles and never force the ICE to recharge the battery out of normal operation).

I appreciate you playing along with this...I'm truly trying to grasp how using fuel is better than not using fuel for FE when the battery in the car is not engaging the ICE to "make it" recharge beyond what the ICE and braking does for it already.

 

Don't feel bad. It took me a while to get my head wrapped around it. I am most certainly not well-schooled in physics.

The lower the SOC, the harder the ICE works to recharge it. So in that second mile, some of the power that ordinarily would be available for propulsion is diverted to recharge the battery.

No problem playing along ... I enjoy the discussion. But you might consider starting a new thread if you'd like to continue it. With apologies to Billinak, I think we've effectively hijacked this one. :redface:

 

Your issue is absolutely your short trips. However, this affects all autos - not just the Prius. Your engine needs to get up to operating temp before it becomes efficient. Five minute trips aren't going to get that done.

You will also see a slight increase after break-in.

... Brad

 

Jimbo - Thanks for the explanation. The part I was missing that you now explained is that when SOC is lower (even if it is above 2 bars on the battery screen) and ICE is engaged coming from EV mode the full potential of power from ICE is diverted to raise SOC (while the rest of the potential propels the car).

And, I apologize to Billinak as well for diverting the thread. But, maybe he got some good info. from this as well.

FYI - I generally do very well with hypermiling in my Prius and I'm in the 62-63 mpg range on my MFD for every tank (minus 2 recent tanks that were 800 highway miles that I did very poorly with 52-53 mpg...hence the 56.2 lifetime mpg sig...the 800 miles are about 1/3 of my lifetime miles). But, I'm trying to gain every available mpg as possible so I appreciate any info. I can gather to be more efficient. I'm well on my way to 65 mpg every tank and will now focus on finding a good balance between EV and ICE to get even better results.

Thanks for the discussion...much appreciated!