I've owned my 2008 Prius for 1 year now. I'm a little concerned about my gas MPG numbers. A few weeks ago I replaced the original Goodyear Integrities with Michelin X-Radials. I suppose the Michelin's have higher rolling resistance. Below is a plot of MPG of nearly every fill-up since day one through now. Any comments?
Ichiro, Well, the decrese in MPG through the fall and the winter -- actually less than 10% -- could be explained by colder temps and ethanol "winter mix" gas. Still, something else could have occured that could also contribute like: A change in residence or job that has a different commute route... Have you ever run out of gas, and limped for a while on the HV battery alone? Have you ever run the 12 V battery down really low -- if so do still have the OEM battery? Do you ever get strange dash warning lights flashing on start-up? Any other weird conditions that required a trip to the dealer to pull codes, etc?
Your summer/winter decrease is really rather small, but I suppose that comes from being in a climate where the temperatures do not differ, radically, during the seasons. It does appear that your MPGs are a bit lower than the average, so I'm a bit curious about your driving style, habits and frequency. Because it looks as though you get gasoline frequently, it is possible you put on many miles. Are these miles all urban, suburban, freeway, rush hour, high speed, low speed, hilly, short trips, auto A/C, many passengers, ... ? Also, do you regulate carefully the pressure in your tires? Answering these questions and the ones posed by Rokeby will allow other PCers to offer some observations and, hopefully, constructive advice or recommendations.
New tires, even of the same type, will usually cause a small hit in mileage. Your new tires have more rolling resistance, so the hit will be even bigger. They will get better with time. Tom
The trends look appropriate. I agree that the new tires are causing a hit. You should see an increase again as the weather continues to warm and your MA shifts forward to include only those tanks after tire replacement. Obviously with as many tanks as you've gone through you put a lot of miles on the car. Can I assume most of those are highway miles? You've been around long enough to know this, but in case not: Slow down and your mileage will improve. It's rare for me to see less than 50-60 MPG on the highway. It's also rare for me to go faster than 55-60 MPH.
That was the first thing I saw when looking at the data plots. "There sure are a lot of points for a car that can get 500 miles to a tankful"
At the poster's mileage and with the bladder it is likely that the OP is getting closer to 320-350 miles per tank. The car's range is well short of 500 miles/tank at the EPA estimated mileage because the usable bladder capacity is only about 8-9 gallons from full to flashing pip. With the amount of miles driven based on tank fills, it appears that speed might be the largest factor. Looks like cruising around 75 mph, but that is just a guess on my part.
My daily commute is about 100 miles and I average about 600 miles per week. I clocked ~31,000 miles in 1 year. The commute is mostly highway between San Francisco and San Jose. On the highway, I try to cruise at 75 mph with a max of 80-85 to pass other cars. My average fill-up is about 8 gallons @ 330 miles. I set the tire pressures at 40 psi, but I haven't checked them in a while... I've been concerned that I'm getting <40 mpg even though the weather has warmed up. You guys are very astute
Tires can really make or break your MPG average. I replaced my stock Integritys with Nokian i3s which are supposed to be very low rolling resitance but my milage still took a big hit and stayed that way with only a minor increase after break-in (over 5k miles). I doubt I'll ever get as good MPG as I got with the Integritys until they come out with a better tires. I'm hoping the new Fuel Max? tires will be better. Also, driving at sustained speeds over 70mph is going to hurt and passing cars at 80+ will solidly drive your numbers down. I know your commute and driving slow with max fuel efficiency in mind is not easy nor safe in many areas so I'm not saying you should atempt to drive that way but I am saying that your milage is low because of it. There could be other contributing factors like air filter, oil level, tire pressure etc. but since I swap between driving for efficiency and driving fast I can see immediate results just from driving differences while the other variables remain the same.
Some would say: "Even a blind squirrel finds a nut now and again." For the speeds you are driving and the newer grippier tires the mileage looks about right to me. At 75 mph my mileage tends to be around 42-45 mpg depending on the weather. Did you also baby the car when you first bought it? I tend to drive new vehicles at pretty tame speeds for the first few thousand miles while breaking them in.
I seem to recall that Ichiro was doing a San Jose to San Francisco (or visa versa) commute and on Hwy 280 (I grew up in SSF and went to SFSU and SJSU so I know that freeway very well) and that he was moving about 10 mph above the speed limit (confirmed by Ichiro). Many things already covered 1. We are in the winter gas blend phase. It should be going away by the end of the month. 2. New tires will hurt MPG's, but give lots of grip. 3. Check those pressures, the will leak air (or nitrogen...heh) over time. 4. Slow down. Yes, I know the race track that is Hwy 280, and yes, between 380 and San Jose it is an absolute blast to drive but move yourself over to the right and set your cruise control to 65 mph. I drive that road, now and again, between SSF and 92 and I cruise it at 55 mph. No one will run you over at 65 mph, they'll be racing in the left lane, not the right.....I know this from experience. 5. We've been having some wind recently, and your mileage will take a hit with crosswinds. Granted, it is fairly consistent and you'll see it in all your fill ups, but don't underestimate how much it can impact your MPG's. 50 miles at 75 mph = 40 minutes 50 miles at 65 mph = 46 minutes 50 miles at 60 mph = 50 minutes Assuming a 50 mile commute, ALL highway miles, All with no traffic (and in my dream world, I'd like a pony), the BEST you can do is save 6 minutes by driving 75 mph vs 65 mph. 10 minutes if you slow down to 60 mph. But your MPG's will move up by 10% (guesstimate) at 65 mph and 15-20% at 60 mph. If you leave 10 minutes earlier (if possible) you arrive at the same time. And think of how much more relaxing it will be when you don't have to constantly scan your rear view mirror for CHP.
I know that the single biggest variable for fuel efficiency is my driving style and average speed... believe me, I've TRIED adhering to the speed limit on a consistent basis. I think that I am just not capable psychologically. I don't have the patience. When I'm going 65 in slow lanes I actually start yawning uncontrollably, and dozing off, no joke. So I know what you mean by a more relaxing pace, but it doesn't work that way for me. Before the Prius (and before I had kids) I used to drive much more aggressively, so I like to pat myself on the back for slowing down as much as I have already. Anyways, my driving style hasn't changed much if at all over the last year. So if my driving is a relatively constant factor, I was looking for other factors to explain the long term downward trend in my fuel efficiency. The consensus seems to be the new tires, and the weather... I hope that as the weather warms up that I can get closer to 400 miles per tank ...
Ichiro, Just because your mind is running at 100 MPH doesn't mean that your car has to do like wise. You might try these to get more involved in the management of your Prius: * Switch to decaff * Get a ScanGauge. With the additional info it prvides there are a number of Hypermiler strategies that become achievable like Hobbit's IGN trick. They require great awareness of traffic, anticipation of road and topography, and minute control of the go-pedal... and great discipline. You can learn to replace frantic response to external stimuli with an internally generated hyper awareness and controlled response with great mileage as a bonus. Prius haters call this condition "smugness." They're dead wrong. It is more like a higher state of consciousness... a positive addiction... an investment in your future. I'm not kidding, think about it... and your kids... and the grandkids somewhere off in the misty future. :cheer2:
Ichiro, try putting in a "books on tape" or some other enjoyable media into your CD player (or ipod). For me, that makes for a less anxious drive, because you're focused on the media ... and the destination becomes secondary. Also, if you're cutting it close on arrival time, leave 15 minutes earlier ... because you then know speeding will result on too early an arrival. You already know your mpg's will increase a good amount, plus, you won't be risking a ticket. BTW, now that your tires are more worn, have the MPG's gone up?
