Gas Mileage Bad on Long Trips.... WHY?

We travel PDX - SF about every 6 weeks in '08 with over 125k. In OR ave. 42, with CA gas 45. Similar driving. Trying EF fuel (now on 2nd tank), but seeing no increase. Need 20% increase to offset costs realistic expecations?. Do I try a few more tanks or go back to E-10?

 

ethanol flex fuel?

 

I can't get above 45mpg at 55 mph.

 

something is affecting high speed travel. either the ice isn't working efficiently and needs maintenance, or something is causing drag. i would look at all the items mentioned in the various posts. how many miles on her?

 

you either? that doesn't make sense, i used to get 60mpg at 55mph in my 04 and 08 all day long.

 

I recently took a trip in my Prius same year as yours. Initially I was in a hurry doing 75 on cruise control and averaged 44-45 mpg. On he way back I was not in a hurry and set the cruise control at 63 and averaged 57 mpg. Big difference!

At 65 speed limit you are not passing many vehicles. You are being passed quite often.

I did not like driving 75. Felt tense. At 63 the Prius feels relaxed and comfortable on the road. I run synthetic. I hope this helps.

 

At 63 MPH I usually see anywhere from 52 to 53 MPG. At 55 MPH I usually see 54 to 56 MPG. That is using cruise control with A/C set @ 76 Auto

If I go up to 75 MPH, the mileage tends to drop off.

 

This is my trip home from Target a few weeks ago. Total distance was about 16 miles, 12 of them on the freeway with the cruise set at 61-63MPH. Freeway portion was probably from 22min to 10min. Oil was replaced by the dealer before we bought it, so unsure what it is. Tires are Goodyear Viva Authority's, OEM size, at 51PSI. I'm a firm believer that running the tires at 51PSI accounts for a few of my MPGs. I might drop them down to ~38PSI in a few tanks to see if there is a noticeable difference.

 

I think it all smoke and mirrors.. *sigh*

 

unfortunately, if the car doesn't throw a code, a mechanic can't do much. but there are a ton of things that can be looked at, call it housekeeping, that can cumulatively reduce your mpg's. from tyres to air filter to plugs to throttle body and on and on.

 

that's not enough for normal wear and tear. what's the latest, any revelation?

 

In severe heat I do this:

Max speed in city: 40

A/C temp: 78

Constant gliding when able (given).

Opt for highway use since the car won't get stuck in a red light and drain the HV.

If I ever get down to 2 bars, which is happening about twice a week, I shut off A/C, unroll windows, and leave the A/C off until the battery gets 5 bars.

REMEMBER TO CHECK YOUR ENGINE COOLANT AS WELL. Even though the ICE isn't running AS often as the electric system, it still needs to be kept cool to work properly.

 

Yes. It's programmed to do so every 5K miles to remind you of an oil change, so be sure to tell it that the oil's been changed if you want relief from it. Other problem may be that you don't completely screw on the gas cap.

 

If you have the A/C set low like you are doing (72) the electric compressor is pulling more juice from the traction battery. When you glide with the A/C on, it is perfectly normal for the traction battery to drop down like you are seeing. As long as you are not seeing the bars go from purple to green or from green to purple in just a few minutes you are fine. If there was a problem, the system would set a DTC code and the check engine light would come on, possibly joined with the red triangle and the word problem on the MFD. Try not to set the A/C any lower than 74 and you should do Ok. You will also find that the A/C system will cool better if it is recirculating.

Green to half charge on the MFD in 9 miles is normal if you are running the A/C like you were especially if you are gliding and not regenerating much and or running the ICE. IIRC, full green (8 green bars) is a 80% charge on the traction battery whereas half charge (4 or 5 blue bars) is around 65%

If you want detailed information on the SOC (state of charge) you might consider investing in ScanGage II.