40 mpg -- What am I doing wrong?

Welcome to Priuschat!

Please see cwerdna's questionaire here:
http://priuschat.com/forums/gen-iii...-answer-these-questions-esp-if-youre-new.html

Have you aired up your tires and mastered gliding?

See Hobbit's HSI guidance here: HSI

Have you checked the oil level? Dealers often overfill.

Be patient with us as we get more info from you. Need to determine the extent to which the car is giving a normal result to some less than ideal factors versus needing to refine your techniques.

 

I bought my Prius V in October. I then spent the next six months in Newport, RI for a Navy school. I was getting around 38 MPG which I attributed to the cold. Then I spent the summer in Dahlgren, VA at another Navy school and I was getting about 42 which I attributed to the heat. Then I drove my car out to California to begin my new assignment and suddenly I'm getting 48-50 MPG without even trying. Maybe the engine just needed to get a few thousand miles on it, or San Diego's environmentals are, in the words of Goldilocks, just right.

 

Please do fillout the questionairre, USEFUL help will follow very very soon afterwards.

Otherwise, you will get a mix of potentially useful help with some not so useful help and maybe some plain ole snake oil.

 

Welcome aboard.

I suspect the 10 mile city drive is what is hurting your fuel efficiency. No car gets great fuel efficiency when first started ... the Prius is no exception, although the warm up time is lessened in the Pri.

To achieve the 50 + fuel efficiency, you must drive a steady speed between 35 and 45 mph. Watch the HSI screen ... when departing a stop light, try to keep the scale out of the red zone, and the "ECO" lit. Get to speed, then try to maintain speed with the HSI scale at or near the center.

Conduct a little test. This weekend, fill the tank and go for a country drive. Drive a steady speed between 35-45 and you will see better than 50 mpg.

I can imagine that you are disappointed with 40 mpg ... but didn't your previous vehicle perform beneath the EPA number as well? City driving, short stop and go trips are "killers." Good Luck!!

 

Please look at your sidewalls & pump another 20psi. If you are shifting into "B" you are losing the regenerative braking. Keep the car in Drive. When the temps drop block the grill with pipe insulation. On 10 mile trips I wouldn't expect much more than the low 40's. Last week I had 15 mile commutes on the Interstate and got just shy of 50mpg.

 

Expect a little less than 50mpg from the V without mods.

You note that you accelerate moderately: something to try on the flat is to try is to keep it in the electric zone until about 15mph and then accelerate steadily to speed in the ECO zone. Adjust for hills.

The Prius is good at start-stop but it's always better rolling. As well as timing lights, when in a line of traffic try to avoid 1-car start stop and creeping (once you stop only move forward when the traffic is really moving again, not when the car in front moves forward 1 foot).

If you're using A/C you're hitting the battery which means you're hitting the engine. With your lower speed, short commute it'll really hurt, especially at start up and it makes it harder to make best use of the EV. When driving at low speed it's better to run with open windows instead of A/C (for mileage at least ), so try to use A/C when you really need it instead of automatically: turn it off before you shut down the car in the evening so it won't come on when you start the car in the morning which I expect right now is your only chance not to use it.

As noted, increase your tire pressures. This trades control and grip for mileage so gradually increase it until you find your happy medium. (E.g. on my 15" tires I found 44/22 a bit skittish on lower-grip surfaces like bridges so dropped the pressure back down a bit.)

As also suggested above you can grill-block (I'm using the common Home Depot DIY Prius grill-block - foam insulation tubes) .
Ken@Japan posted a grid of upper and lower grill-blocking with temperature ranges. (http://priuschat.com/forums/gen-iii...62556-2010-prius-grill-blocking-strategy.html) 90F is about the summer limit here. To err on the side of caution I'm running a 50% lower-only grill-block and I was using a 100% lower-only grill-block in winter. (The upper grill is the more important one for cooling.)

 

Your tire pressure is way too low @ 30. Pump it up to at least 40 or more (depends on when you think the ride is acceptable) but below the max on the side wall. Pump the rear tires 2 psi less then the fronts.

Look ahead, way ahead for traffic stoppage, and coast to stop for longer distance.

Try to make sure the car starts from stand still in battery power only untill at least 10 mph or higher, then step on it to accelerate crisply. You don't have to baby the gas peddle for acceleration. The engine is more efficient at medium load. I even set it to PWR mode all the time and still averaging 57 mpg. If you prefer ECO mode then you do have to really step on it a bit more.

Easy on the gas when accelerating uphill. Let the speed slip a few mph uphill would help mpg. Anticipate the coming downhill glide. Leave a longer distance between yours and the car in front so your glide downhill can collect more momentum without having to brake too soon when your car catches up to the one in front too soon.

Once the car gets up to traffic speed or your desired speed when you are alone, set it to cruise control, even if it's not very far from the next red light. Cruise control finds the most efficient gear ratio and power source combination that your foot on the gas paddle cannot replicate easily.

When you are more familiar with the car then try to learn to glide in neutral (pull the gear knob towards yourself for 2 seconds) before stopping, or on long but slight downhill slopes. Make sure you put it back to "D" gear before full stop.

I forgot, one more thing. Anticipate stoppage way ahead and tap the brake lightly so that the car slows down by the electric motors regenerating the battery. Only floor it at the last moment to kick in the hydraulic brakes.

Be patient, the car will also get better mpg after breaking in.

Happy Priusing!

 

I believe your tire pressure is way too low. I would recommend that you keep your tire pressure at a least 40psi (Front) and 38psi (Rear).

I personally never trust the people at tire shops to check my tire pressure, there are too many inconsistencies! I would also highly recommend that you purchase a good tire pressure gauge (not a pencil gauge) and an air pump. Always check your cold tire pressure at least every 2 weeks or once a month (minimum).

 

Well, you're already getting almost double the mpg of the BMW! What is the state of the battery normally? If it's constantly falling to two bars, the engine has to work hard to charge it as well as move the car. That's the one advantage of a steep hill, you can recharge fully on the way down!

 

i would NOT recommend inflating your tires to 40+. Just follow the mfg recommended pressure i think its 33-34 psi. Increasing it anymore, you'll be in for a shock with the sudden lacking of handling. don't expect to fill your tires to 50 psi and expect a 10mpg increase, that's not happening.

The reason you are experiencing low mileage is because your commuting trips are so short. Ethanol fuel also have something to do with lower mileage as well, but 10% of 50mpg is 5 mpg so you should average 45-46 which is what im averaging city driving. i run my a/c constantly because its really hot outside.

 

Glad to see others with similar MPG
I have a 9.5 mile commute usually with traffic and a lot of going up hill in the morning. My average from day one is now finally 40 MPG at the beginning it was more like 35.
My best tank was 46 but i know that I did trips with over 50. (The car computer showed 56)

 

Is it a bit stupid that fuel with 10% ethanol increases fuel consumption by 10%. Why not just leave out the ethanol and use the same amount of petrol?

By the way, you will get a significant improvement in fuel consumption and handling by inflating your tyres to 50 front and 48 rear although that is on 15 inch wheels not the 17s like you have. However it cost nothing to try it.

 

Tire pressure is a significant part of the issue. The ride will be harsher at 51/49, so try 40/38 or so and work your way up. 30 is too low. Never go below the placard on the driver's door jamb. I would run 51/49 because it gives me higher mpg, but I run 42/40 because my wife drive's it daily, not me. My Ecopia (15's) have sidewall max of 44, so when I take it on a solo road trip I use at least 44/42. Just find your preferred balance.

You did not answer about oil level. Has your oil been changed by you or by the dealer or by another shop? You really want it at or a little below the top mark. Some places put 5W-30 dino oil in. It needs the thinner 0W-20 for max mpg, and it only comes in synthetic.

Now, several have said your mpg is low because you only commute 10 miles. My experience tends to refute that. My commute is 1.5 miles each way, and my wife & I get close to 50 mpg on it. Low tank was 40 mpg in 0F winter temps with snow & ice, defrosting, etc. Our lifetime average is 50.5 mpg since December 18 purchase. Of our 12,500 miles, about 8,000 miles is highway trips averaging low 50's mpg, so the commuting and other local driving is mid-high 40's. We just get in and go, but our commute is 2 gentle pulses to 40 or so, and then gliding. In other words, we are not using the ICE hard while it is cold. When I can go even 5 miles in town, I can raise the trip fuel economy from 53 or even from 55 with pulse & glide in the 35 to 40 mph range. Please read Hobbit's HSI page I linked above and be sure you understand the difference between gliding and no throttle. Keep light throttle so that the HSI bar disappears. At 40 psi or so, your glide distance should be 20% or so longer than at 30 psi.

It seems universal here that the trip mpg is overstated, as you have found. Mine averages 4.8% high. That should be about the same for you. Some of the first ones were 10% high. So don't sweat it, but the trip mpg should be around 53.5 to equate to the 51 city epa mpg.

If you are coasting with no throttle, and given 30 psi, 40 is not surprising. With the psi recommended by most here, and with proper glide technique, you should readily reach epa city IMHO.

 

It doesn't need to be this complicated. Half of what you're talking about will add 2-3 mpg put together. But the rest is good advice for the OP:
* Increase tire pressure (I think 40/38 psi is fine, after that it has less effect on mpg and more effect on rough ride).
* Anticipate stops, so you can coast when possible. Avoid complete stops if possible. Except one stop for 3-5 seconds after a couple miles to get into stage 4 (I think the 2010 is the same in that regard) so that the engine turns completely off.
* Make sure you're driving in 'D' (normal gear for forward driving) not 'B'.
* Ethanol could be big factor. But ethanol improves air quality without damaging the water supply like other additives can.

But I disagree (to some level) on these:
* If you have a steady foot, cruise control is not needed and doesn't allow for anticipation of hills, etc.
* Accelerate normally. You want to use all-electric power very sparingly. The battery is there so the engine can turn off at lights and when coasting, and on rare occasions where you really need to accelerate hard. (Battery gets its power from the gas engine, but with losses along the way, so it's less efficient than using the gas engine directly)
* Gliding in neutral should be learned, if at all, after normal gliding (no arrows on energy graph), since neutral doesn't provide regeneration and is a more limited use case. And some people are nervous about not being able to accelerate while in neutral, especially in a city commute.
* oil overfill might make a 1-2% difference, grill blocking can help a little in the winter, these are not the problem here.

Have you considered other routes that would have fewer starts/stops? You also want to avoid routes more than 60 mph, but for 10 miles each way, I would think you should be doing upper 40's mpg anyway.

I have a 3 miles commute and it really hurts my mpg, but a good deal of my miles come from longer weekend trips and such, so it brings it back up to 49 mpg lifetime average. I used to have an 8 mile commute and the difference is notable in the winter.

 

Hi G2,

I see that your trips are about the same for me, I drive about 10 miles each way and I'm getting about 40mpg also, I'm pretty sure it has to be with the relatively "short" trips that you and I both have. I think the 50mpg will be there on much longer trips as our commute is just too short to see the benefits. Of course I'm only on my 2nd tank as I just picked up my Prius 8/1/2010 but you've been driving for over 10 months...

that being said, I'm trying a few new things on my 2nd tank mainly watching the On screen INSTANT MPG and trying to keep that bar chart between 50 & 100mpg, I try very VERY hard not to let that dip, in another week or so when I do my 3rd tank I'll report back and see well I did. Cruise control even for the "short" 10miles at 55~60mph seems to work wonders for the BAR GRAPH... The car is much much MUCH better at keeping the gauge at or near the 50mpg mark better than I ever could manually... Give the Cruise Control a try and see if that will help you out, as it seems to work for me...

My driving Mon~Fri work commute is 10 miles each way. Weekend local driving/shopping/kids & parks, again all local short trips...

On a POSITIVE note, I'm getting 300% better mpg than my V8 Lexus GX470 and I'm only paying 1/3 the price at the pump and less fill ups so for me NO COMPLAINTS... just "slightly" jaded, like you, that I didn't see the magic 50mpg. Here's hoping to you and me both with our short trips and CRUISE CONTROL that we'll be able to OBTAIN this goal...!

PS. There is NO other vehicle with better GAS mileage than the Prius, so you still picked the right car, another vehicle would have already returned poorer gas mileage than your current Prius so be positive and thankful that you're getting the 40mpg vs. 25~30mpg that other vehicles would be providing to you... Just helping you and ME to manage our expectations a bit better...

 

nerfer, great advice for the OP. FYI, the 2010 does not need to stop to reach stage 4. Just a sub 45 mph glide or coast after sufficient warm-up. It also skips the entire warm-up cycle if initial engine temp meets a threshold. See genIII warming up stages thread.

 

lw69: With practice, P&G will crush cruise control. Think 70+ versus your 40.

OP: with your flat terrain (like mine in south-central KS), you can use a narrow speed band like (in posted 40 mph zones) 42-35, or a wider band like 45-30 if traffic permits, and just destroy the epa.