- Have you read This Thead Yet? YES -- Good info - What fuel economy are you getting and how are you determining fuel economy? (trip computer or manual calculations) When the winter started here in VA couple of days ago with the snow storm the MPG dropped by about 10, from 42-45 to 32-36. I calculated this by trip and by the gas fill-ups. The MFD still shows 45 MPG average. - What fuel economy are you expecting and why? Around 45 MPG, if not at least 40 - What are the approximate outside air temps? Under 40 from now on. - How long are your trips? Some long, more than 25 miles one way but majority will be within 5-10 miles. - How much of it is city vs. highway? Roughly what's the average speed in overall and and of each segment? Is there a lot of stop and go driving? Mostly city, so speed is less than 50 MPH. - What region/state are you in? (if you haven't set your location in your profile) Northern Virginia. - What's the terrain like of your drives? (e.g. flat, gentle hills, steep hills, etc.) Generally flat. - Is your oil overfilled? (i.e. above the full mark on the dipstick) No - How old is your 12v battery? What is the voltage reading of your 12v battery after sitting over night? (Method Here) Battery should be the original one. I have not checked it but will do it today. - Have you had your alignment checked? Any pulling or abnormal tire wear? New tires, just got them a month ago. - Are you using the factory tires and wheels? If not, please indicate tire make, model and size (e.g. Goodyear Assurance Fuel Max 185/65R15). Goodyear from Wal-mart. - What are your tire pressures? Not sure, I will check that as well. - Make, model, year, engine and transmission of previous car? (e.g. 08 Honda Civic Si 2.0L 4 cylinder, manual transmission) What did you actually get on the same trips/commute? (Please give us actual numbers, not EPA ratings.) Other car is 2007 BMW 335i. The EPA on that is pretty bad that's why I have a Hybrid - How are you trying to drive (e.g. trying to stay in electric only?) and how hard are you braking? Yes, trying to stay in electric. - Are you "warming up" the ICE (internal combustion engine) by letting it idle after powering on? No. - Are you driving using D or B mode? D - HVAC settings? Are you using the heater, AC, auto mode, etc.? If using auto, what temp is it set to? Heater is on most of the time. I keep the car temp around 72-75. - If reporting a mileage drop, did anything significant change on your car (e.g. accident, hit a curb or big pothole throwing off alignment, oil change/other maintenance/repairs, changed tires or wheels, etc.) or your commute? I just changed the Engine Air filter. Getting ready to do the regular services, planning on: transaxle oil, engine coolant and spark plugs.
Winter always hurts. See Why mileage gets worse in winter. Short trips also hurt mpg. But they hurt even more in traditional cars. In a 2005, the original 12V battery should be on seriously borrowed time. This is often a source of strange problems and reduced MPG. Very important point. 'unknown' pressure is usually too low. Generally a bad idea, as this creates needless mechanical -> electric -> chemical -> electric -> mechanical conversion losses. Except for special, short distance circumstances, try to minimize electric-only motion. Heater use forces the engine to stay on longer, and often prevents it from turning off at stop lights. For best MPG, minimize heater use. Or for comfort, simply acknowledge that use of the heater will reduce MPG, and this is just a normal cost of winter. The air filter should have very little impact on MPG.
all good points above although, a seriously dirty air filter could affect mileage. new tires and winter gas. are the tires low rolling resistance? if so, mileage will improve as they break in. if you want to learn to drive efficiently, you should get up to 45 in winter and 50-55 in summer.
Fuzzy and bisco covered it. Don't expect your new tires to deliver maximum mpg until they are well broken in. Usually a couple thousand miles will do it. Also remember that ANY water on the road, be it liquid or frozen, will reduce fuel efficiency as will very cold temperatures. The Prius engine is small and has a hard time staying at the optimum operating temperature so it will run more often to keep itself within operating parameters. This can really hurt mpg. Look into installing an engine block heater, grille block, and a warm coat so you can minimize heater usage. lol
Agreed w/all of the above. Also, since we don't know what model and size of tires the OP put on other than "Goodyear", if they're of the "wrong" model, he may never easily see the mileage he did w/the stock tires. Even if he replaced the stock Integrities with new ones, he could see a drop as described at http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=177. BTW, OP, for "The MFD still shows 45 MPG average", are you resetting the MFD at each fill up? (I do.) If not, I believe it will have be averaging the mileage since you last reset it. If you reset it now or at the next fill up, I suspect it will yield lower numbers, more in line w/your manual calculations.
Probably a combination of the cooler weather and the new tires. BTW. What is the exact model/size of your new tires ("Goodyear" is just a brand name. It gives no model or the size information). Also check and report the tire pressure.
Tires: Goodyear Viva 2 Tires P185/65R15 -- I don’t think the drop in MPG is because of tires as I replaced those when I bought the car in end of July. I was getting close to 50 MPG on HGW till a week ago with the same tires. Tire Pressure: I was not able to check that but it seems low, so I will get that fix later today. Hopefully that will increase MPG a little. 12v Battery: So I did the test early in the morning, before starting the car. At ACC mode it gave me 11.8, it changed to 11.2 when I put the current load on it. The reading changed again to 14.2 when I started the car. @fuzzy1 -- Thanks for the info, I guess it is just the normal winter weather MPG drop but I thought it would be around 5 but for me its actually 10-15 MPG which is huge so I was little concerned. @bisco -- Yeah still learning to drive Prius at its optimum capacity. Hopefully I will learn quickly @F8L -- I like the coat idea ... The winter here is not extreme so I think most of the time I should be okay. This sudden drop got me worried so I starting researching a little. @cwerdna -- The tires are OEM size so I don’t think that is the problem and yes I did reset the MFD with every fill.
Goodyear Viva 2 Tires P185/65R15 are not LRR tires, you can do better next time. (in another 50,000 miles) Your 12v Battery is old, anything under 12.5 is suspect, you are way under. For about $140 (and tax and labor) you can get the Toyota OEM battery at the dealer's parts counter. For $170 You can get a Optima Yellowtop D51 with a kit to make it fit a Prius from Toyota Prius 12 Volt Auxiliary Battery with install kit for 2004 - 11 For about $200 you can get a Optima Yellowtop DS46B24R battery just for the Prius that is a direct fit from http://www.optimabatteries.com/battery_selector/ (The Yellowtop is a better battery, it is up to you if it is $60 better) (Under certain failure modes, the 12 v battery can cause a mileage drop)
I agree with Jimbo, this is not good. I haven't been a Prius owner long enough to change this battery, but all my traditional cars needed battery replacement due to starting problems before they got this low. But a Prius does not provide the traditional and familiar weak battery clues. The voltage after starting is set by the inverter, not by the battery. Your measurements in the morning before starting the car are the important figures.
