Colder weather has zapped my mileage to 44mpg

What were your averages per tank this summer? I can't image needing grill blocking in CA. What is your typical commute like? What are your tire pressures?

 

Below 86F ambient temperature, you are a good candidate about a grill blocker.
http://priuschat.com/forums/gen-iii...62556-2010-prius-grill-blocking-strategy.html

Ken@Japan

 

I'm collecting lots of data that will show nicely the influence of temperature in hwy FE for the 2010 Prius. My first set of data (10 hwy trips - 360 miles each) has been posted in this sub-forum in a different thread, but I will soon have 10 more to show in that thread... By the time my Prius turns 1 year old in 2010; I will have near 100 trips for a nice analysis.... and plan to send the data to Toyota!


All I can say so far is that the Prius FE is a huge disappointment in cold temperatures... With 99% hwy, like I do, the MPG drop is huge (10+ MPG or 20%! based on preliminary data)... I was not expecting that much drop at all since my hwy trips are long enough to preclude major hits caused by engine warm-up time... I'm not sure what the explanation is but similar experiments in my previous CR-V and my current Odyssey have revealed a MPG hit of maximum 5% in the winter...

 

Have you factored in Winter fuel formulation change? Have you tried grill-block and EBH? Do you have a Scangauge or other method to track engine/coolant temps? Highway speed at cold temps can really suck the heat out of the engine!

 

I know about the winter blend, but like I said before, the hwy MPG hit in the winter has been around 5% or less, in my other cars, not 20% like in the Prius... all my cars get the same gasoline from the same gas stations.

No. I don't like the idea of grill blocking for my hwy trips. My Prius basically drives hwy only and they are long trips. The effects of engine warm-up should be negligible. I can pretty much explain the MPG loss in my other cars in the winter. The <5% loss is likely due to gasoline winter blend + increased air drag in colder temperatures + engine heat loss caused by the heater + occasional use of defroster. But, the 20% loss in the Prius is something I'm struggling with...

Grill blocking in my hwy trips would require a scangauge for sure because it can get dangerously hot in most cars... most people agree that those who drive hwy only, like me, should not bother about grill blocking... and that was true for all my cars except the Prius... But, I don't plan to block its grill and spend money with scangauge yet…

I know all of that, but still, 20% is huge… so far I have found the Prius FE to be disproportionably lousy in severe winters and I haven’t travelled under near zero or subzero temperatures yet… (My trips are in northern IN, IL, and south WI). I’m afraid my Prius will struggle to keep above 40MPG (indicated) when that happens… very disappointing…

 

I was getting a little over 50 mpg on average now about 46-48 mpg. Im driving about 70 miles per day combine city hwy. I raised air pressure to sidewall limit. The wheather here is in the 40's in the morning lately. The only maintenance so far is an oil change. Sometimes Im taking it out of ECO. Maybe consumers guide was right driving it normally can be about 44. When I first got it in the summer I thought it was easy to get in the 50's and higher.

 

A Hybrid Owner’s winter survival guide - CleanMPG Forums

 

That's surprising. Was it raining or snowing there?

We are in the 40s now and my MPG has not been noticeably affected. I garage at home but not at work.

 

It makes sense that a car designed NOT to waste as much energy would be affected more by the thermal loss than typical cars that run their engines all the time, producing waste heat year round.

There are techniques to improve your mileage, including techniques to mitigate the winter hit. Read A Hybrid Owner’s winter survival guide - CleanMPG Forums and decide what makes sense to you. The grill blocking would help alot. Get a scanguage and watch the ambient and coolant temps. An EBH would not be a big deal for your long highway drives. What is your tire pressure?

Good luck!

 

Totally agree with that statement. The Prius seems to be very sensitive to its environment. Although I am losing a bit now during the winter, I will make it back up in the summer.
Indy shouldn't have any problem with lower grill blocking. The inverter radiator is behind the upper grill.

 

Wolf2000, most of my trips have been dry so far except for one with light snow for about 20% of the time and occasional ones with light rain. When I have time, I'll plot my 20 trips including data about cargo weight, weather, and average speed for each one. However, just by scanning the data collected so far, I have noticed that the single most important factor in HWY MPG in the new Prius is temperature, although, of course, speed, rain, snow, all of that has some impact. My MPG started out as 54 or so in the middle of fall (which is when I started the hwy trips) with average temps during the trip above 50's and it has dropped to around 43 under current temps of 30's. That's a 20% drop... very impressive. My tire pressure is 48/46 by the way… so tires are over inflated. Again, similar experiments in fewer hwy trips with my Hondas CR-V and Odyssey last year revealed a MPG drop bellow 5%, which proves that, even with 100% hwy and long trips, the Prius is very sensitive to temperature drops.

Spider, I think the investment of buying a scangauge to monitor coolant temperature is not worth in my situation because of the nature of my driving (99% hwy - long trips). The blocking may help a little but I doubt it would result in any significant improvement under my circumstances....

 

Grill blocking is MOST helpful on short trips since it reduces the initial warmup. In my experience, it is SIGNIFICANTLY helpful on long trips in any car by maintaining heat. It is more significant on long trips in a Prius, since the Prius will run the engine solely to keep the emissions at their lowest level.

The EPA tests reflect a fixed operating environment. Prius blows every other car away in that fixed environment. By virtue of pulling out all the stops for that MPG result, it falls off more in adverse conditions. But you can mitigate the dropoff if you adopt proven stragegies, such as grill blocking. It will still vary more than other cars. The bigger they are, the harder they fall; and Prius is as big as they get in mpg.

 

Doing the math, the extra cost of grill blocking plus scangauge cost will hardly be justifiable in my situation. Sorry, but that's the way I see investments in hybrids. If I cannot justify their gas savings financially, then, I've got plenty of better options to choose from. That’s just me.

Wow, your MPG hit is 27%!!! You are right, 42 MPG is still good, but hey, what is the EPA estimate for the Prius? I don't really care if it is still better than most cars, but I hate to buy a car that carries a misleading label on it, especially when it regards the most important feature of its marketing strategy, the MPG! I'm sure that any non-hybrid would never give you a 27% hit in your commute. All my other cars (most of which were Hondas) always stayed close to EPA in the winter or in adverse conditions and way better than EPA in summer or better conditions… Unfortunately, I had the same expectation for the Prius but what a disappointment…

 

Thanks for the info, very nice, but like I said above, I would have to drive impossible mileage to justify a scangauge and grill blocking at this point. Besides, I just don't like the idea of worrying with things like: what do I block, what I don't block, what material I use to block, at 80MPH this thing is getting hot so I better stop and remove the darn grill, etc... You know… if I have to buy a barbecue grill that requires manipulating all small pieces of it and buying extra stuff to make a good steak, I may well just skip that and buy a good grill instead…

 

Welcome to the world of labeling frustration we've been dealing with for years. We've had to take it upon ourselves to spread the word in forums like this and on websites.

Those extremes, like sub-zero temps, still are not taking seriously... despite the fact that some of us see them routinely.

And don't focus on just Prius or hybrids alone, take a look at how Volt info about this topic is practically a complete void still. There is tremendous opportunity for consumer awareness improvement.
.

 

I was about ready to give up on this but I just wanted to add that a ScanGuage is not necessary. If you just block the lower grill with like $6.00 in pipe insulation I really doubt that you will ever exceed the engine operating temp (during the winter). With that said, if you do, the idiot light will come, you pull over, remove the blocking and continue on your way.

Too simple and cheap not to at least try it.

I blocked my grill w/o the guage. I just happen to get one for Christmas (not opened yet).

 

:drama:

When the idiot light comes up in the hwy, it is often too late, don't you know any better? I drive often at 75-80 MPH over 350 miles!

Why take such a risk in face a few MPG improvement and all worries that goes along with it? Sounds a very silly thing to do...

 

Good point but EPA estimates have worked well for all my cars except the Prius...