Lower MPG than usual

not likely. could it be the dropping outside temp?

 

how many miles on her? have you checked all the usual suspects?

have you done the prescribed maintenance?

 

If you had a truck that got 10mpg and then it only got 9mpg it would be barely noticeable... But it you have a Prius and it gets 50mpg and the drops down to 45mpg that would be noticeable. Funny part is both of those differences are the same 10% decline in MPG, its just the the Prius seems like a lot more.

More to the point, very small subtle things can change gas mileage... Low tire pressure alone can wreak havoc on MPG, but same with cold winter weather using the heater on full blast or hot summer weather with air conditioner on full blast. Ideally, driving 40-50mph in 75-85 degree weather seems to be the sweet spot for the best MPG for Prius.

Also driving conditions and who you buy gas from is key too. For example my drives to California from the Pacific Northwest shows 43 or MPG in winter in the rain, but then I get to California and buy their more heavily regulated higher quality gas and drive on dryer much newer roads and my MPG shoots up to near 50mpg right away

So to answer you question, start working on your car and do everything possible to improve gas mileage, do basic maintenance and you'll see a boost. Alos experiment with adding a pound or two PSI at a time in your tires, then once you notice less traction let a little air out. Myself and other prefer a tire in the 45psi range.

And keep in mind people who are only getting 35mpg in their Prius in many cases don't have anything wrong with their car that needs to be fixed, just lots of little things that need to be further refined.

 

no, you won't get an indication until a check engine light comes on. but plugs are only one possibility at that point.
toyota recommends changing them at 120k, but if you would feel more comfortable doing them now, the oems are pretty cheap, and the labor is a bit fussy.

otoh, the sooner you change them, they less likely they will be frozen in place.

 

The recommended change time for the plugs is, if my memory is right, 120k miles. However, I did not notice that the dealer I was using at that time neglected to change them. A little after 200k miles I was stopped at a traffic light when the engine started sputtering & choking like it was misfiring on 2 or 3 of the cylinders. There was NO OTHER INDICATION OF A PROBLEM. My current dealership was around 200 yards down the street so I got the car there - where the factory plugs were replaced with new ones.

So, you can probably go more than 120k miles, but I would not recommend trying to push it to 200k.


(Original owner, 2004 Prius, over 200,000 miles)

-Graeme-
2004 Prius with >190,000 miles.
Sent ?.

 

I replace my plugs at 120K... It was a waste of time... The plugs still looked almost new even after 120K... These engines run cleaner than anything I've ever seen....

 

I don't see where you stated how much your mileage actually dropped. Have you physically calculated it over multiple tanks to arrive at your conclusion it's going down?

Among the "usual suspects" Bisco refers to in Post #3, how old is your 12v battery? That has an affect on a lot of Prius systems but an early sign it's going can be a reduction in mileage.