I just had an oil change and tire rotation and my fuel economy dropped to 35 MPG from 48-52 MPG (only a 6 min commute here). I wonder if this is a coincidence since right about then the temp dropped to about low 30 deg or is it possible they messed something up in the rotation?
Several possibilities: They reduced the tire pressure. They overfilled the oil They changed to a higher viscosity oil The lower temps cause the ICE to run more. Most likely, it is a combination of the things listed. jrohland
Looking at your sig it seems that if you had a shop do the maintenance then you gave them the oil to use; you list the correct weight of Mobil1. It is probably related to tire pressure. Shops have this annoying habit of lowering the tire pressure to the "industry standard" 35psi. Annoying at best. Check and adjust tire pressure first and then move onto other areas. Oil overfill is one of the most over talked and overrated issues about the Prius. The overfill conditions which would cause crank slap or other very bad conditions of overfill don't happen with a 4 qt fill. The only way that the oil in the sump would cause a fuel economy problem would be if there were some interference between the crank and the uncirculated volume of oil in the sump.
Thanks. I will check the tire pressure. I totally forgot to tell them to leave the pressure at 42 psi when I ordered the tire rotation. They gave me about about 1/3 of the 4th qt of oil so I they did not over fill it unless they did not totally drain the previous. I had planned to do my own oil change but being on business trip has made that a PIA. Thanks I will wait it out and see how the warmer weather back home changes things and will check out the tire pressure.
Holy smokes. What a difference. My tires were at 32 PSI so after bumping it back up to 42 PSI. My fuel economy jumped back up to 50-54 MPG after a long trip sightseeing.
I feel pretty confident in saying that most issues with FE after a shop service are related to tire pressure. That is the first thing I check and that is nearly always the problem. Some shops ask you what you want for tire pressure, I know my local Costco does, but others just put in whatever they feel like putting in, not even following the manufacturer plackard that is on the driver's B pillar. I honestly wouldn't be so anoyed about the tire pressure thing if they were reverting back to the factory spec, but they usually don't even do that.
Actually, with only a 6 minute commute, I am suprised you get such good mileage. Sudden cold weather is most likely your problem.
