Decreased MPG following 1st oil change

I thought I saw a number of responses out there about incorrect weight, overfilling, and asking if you've driven a full tank or not. You might double-check before reposting in a separate forum.

 

Check to make sure that the oil isn't overfilled. If it is, take it back to the dealer and have them take out the extra oil. Check your tire pressure settings. Many drivers use 40/38PSI or more.

 

Suggestions:

1) Ensure they used the correct Oil weight 0W20
2) Ensure it's not high on the dipstick or overfull
3) They may have adjusted your Air in your tires, if so check and adjust back.
4) The 20 MPG drop seems hard to believe related to a service

 

Service people left the emergency brake on?

 

Service people left the car on in ACC, IG-ON or in neutral when READY, and damaged the 12V aux battery? Some people have reported increased fuel consumption if the 12V is weak, as it presents a high electrical load.

I don't know if it's possible to see the 12V battery's voltage on a Gen III car. On earlier cars there was a 'Vehicle Signal Check' menu in a hidden menu on the MFD, but I don't recall anyone mentioning how to do it on the 2010.

In HTMLSpinner's Bluetooth Mic Volume Adjustment Video, at 0:42, you can see a Vehicle Signal button in the upper right. Perhaps the 12V voltage is hidden behind there? You will need to have the NAV system for this to work, though, I don't know of a way to access a hidden menu if you don't have NAV.

 

After taking my 2010 Prius to the dealer for the oil change the sticker said that I needed to return in 3k miles for the next oil change. The sticker and invoice did not state what weight oil was used. Needless to say, I now change my own oil. Bought a filter wrench and use only 0w20.

When I called the dealer they said they used the correct oil but did not know what oil that was. They could not give me a believable reason for putting 3k on the sticker for the next oil change, if synthetic oil was really used.

I change my own because I want to make sure the proper oil is used on my Prius. My local oil distributor also sold me a case of filters as a good price. It is a little cheaper, too.

 

good move. pathetic dealer, who it was?

 

The smart money is on the wrong oil. Bet they used 5W30 (gen2 oil).

A number of UK gen3 prii owners have had this happen.

 

How do you know it has dropped from 50 to 30 mpg? Did you reset one of the trip indicators after you got the car back to check it? Sometimes dealer service people leave the car in the Ready mode for hours and it runs to keep the battery up and uses fuel without moving, very bad for mileage. A more likely scenario is that they accidentally reset the Trip indicator while trying to reset the oil change indication and your mileage is only what you have gotten from the dealer to wherever you are now.

Things such as tire pressure, type of oil, oil level, etc will have an effect but usually not that drastic. If it were me I would check my tire pressures and look at the oil level, then I would reset a trip indicator and drive for a hundred miles or so to see what the mileage indicates.