After fill-up, estimated mileage range 100 miles less than original

not much value in that metric. have you ever driven from full to empty to see how many miles you get?

do you keep track of mpg's when you fill up?

do you use a trip meter to track mpg's?

 

Bisco's questions might get you on the right track. The DTE is based on previous performance. If it's fallen, then that seems to indicate that your gas mileages has fallen recently. In fact, one of our members (@Salamander_King) has expressed his opinion that DTE at fill up a good indicator of how you did on the last tank. As Bisco said, though, the DTE number is not the main thing. The only number that really matters is the result of dividing the miles driven on a tank by the amount of gas used. Unfortunately, that's a virtually impossible number to find on a Prime. Perhaps you might try starting with a full tank and driving for maybe a half tank in only HV mode and then full up again and calculate the mileage.

 

Yap, as others commented DTE is just an estimate of full tank distance using only HV mode based on past performance. I am not sure if it is strictly on the last tank only, but most likely only for very recent HV drives. Look at this thread. What is your DTE after fill-up? | PriusChat My 2017 PRIME's DTE ranged from 574 miles in the summertime to 450 miles in wintertime. The difference is roughly what I expect from the seasonal differences in HV only mpg.

summer mpg 61.6 (573÷ 9.3)
winter mpg 48.4 (450÷ 9.3)

where 9.3 is the gallon of gas used from fill up to empty light comes on (2 gal less than the tank capacity).

 

40 mpg is pretty bad, unless you're racing

 

Do you charge your car? Driving EV will inflate the mpg since you are not using gas but the car is recoding the miles. In any case, your 40 miles per gallon is very low for PRIME. What type of driving conditions? Speed, distance/trip, use of the heater, ambient temperature, any hill climbing?

 

Our 6,000 mile trip last May gave me quite a bit of highway HV driving data. My worst tank ever in a Prime was last May. Driving east across Iowa into 50 mph headwinds. The wind slowed everyone down to about 50 mph. On that tank I got 42.02 mpg. A few days before, while touring Colorado, I got 61.57 followed by 65.55 mpg.

It's hard to imagine only getting 40 mpg in a Prime. Something is really wrong , which I guess is what initiated your original post.

Given that it didn't use to be this bad according to the change in DTE, something has changed.

It could be dragging brakes. Filters. Tires. New tires cause a hit to mpg and especially if they are not low rolling resistance tires or the wrong size. The heavier than spec oil is causing some drag, but that can't be the whole problem. How about the panels under the car. Any damage there bad enough to increase drag?

I'm just guessing. It sounds like it will need a good going over to sort out what's different unless you know of something you might have changed to cause it. The tires are capable of making a big difference if they are the wrong ones.

 

If you are really getting 40mpg then it explains why you are getting 425 miles on DTE after a fill-up. The car is using the last tank mpg for the estimation of the DTE. 425 miles is about 45.7mpg (425 ÷ 9.3), is it still higher than your calculated mpg, but close.

New tires will lower your mpg, but by itself, 40mpg is too low. If you were using 5W-20 oil, that also lowers mpg. Have you had cold weather? You may have had combinations of mpg lowering factors together, but yeah, I would check what @jerrymildred suggested. Brakes and undercover for sure.

 

did you ever check your mpg at the pump when you dte was 525?

 

1) Look on top of your Oil Fill Cap under the hood: it should say "0W20" 5W20 is not that different, but no reason not to use the recommended. 2) "New 4 tires" will always change the MPG immediately! Especially if you don't the buy the fuel efficient, low rolling resistance type. Also, tires vary in weight. Maybe you bought heavier tires. Maybe the tire shop did not inflate to the most efficient pressure. Bottom Line: whenever the car changes behavior suddenly, always look at the last maintenance item you did on the car--change tires? Check your tire pressures.

 

Are these non-stop miles; highway or urban, etc?

 

Can you more specific regarding the Bridgestones? Post the full name of the tire.