Low interstate MPG

So next week I'm going on a road trip to Savannah GA. So all higher speed driving (70-75 mph). But for some reason my car gets rather now low milage, in any driving other then city driving. i average about 42 mixed and about 38-40 highway. The funny thing is, when i drive in the city my mpg is ranges from 40-100 mpg in 5 minute segments.

So sense my car still gets good city mpg i feel like my battery is still perfect! But when ever i drive down the road it seems to only get about 35-45 instantaneously. with no hybrid assist. It leads me to believe my ICE is inefficient. It has new spark plugs, new Toyota ATF-WS, New oil and filter, and new air filters. Oh and the tires are inflated to 38 front, 36 rear.

So to sum it all up I'm worried i will only get about 35 mpg with me, 3 friends, and all our luggage in the car next week. Sorta disappointed because my sisters 2005 gets 45, loaded down with stuff at 78-80 mph. Thanks, Aaron

- Have you read This Thead Yet? yes

- What fuel economy are you getting and how are you determining fuel economy? (trip computer or manual calculations) 42 per MFD

- What fuel economy are you expecting and why? 45-50. because thats what my sisters 2005 gets and she doesn't even try to get good mpg.

- What are the approximate outside air temps? 65-85

- How long are your trips? mostly 30 mins

- How much of it is city vs. highway? Roughly what's the average speed in overall and and of each segment? Is there a lot of stop and go driving? mostly back roads, 45-60 mph, and some city

- What region/state are you in? (if you haven't set your location in your profile) TN

- What's the terrain like of your drives? (e.g. flat, gentle hills, steep hills, etc.) slight hills

- Is your oil overfilled? (i.e. above the full mark on the dipstick) nope

How old is your 12v battery? What is the voltage reading of your 12v battery after sitting over night? (Method Here) seems pretty new, yellow top optima, about 12.2 volts, 14.3 car on

Have you had your alignment checked? Any pulling or abnormal tire wear? nope

- Are you using the factory tires and wheels? If not, please indicate tire make, model and size (e.g. Goodyear Assurance Fuel Max 185/65R15). sadly they are not LRR new nexen tires. and can't afford to replace new tires

- What are your tire pressures? 38, 36

- Make, model, year, engine and transmission of previous car? (e.g. 08 Honda Civic Si 2.0L 4 cylinder, manual transmission) What did you actually get on the same trips/commute? (Please give us actual numbers, not EPA ratings.) 2004 volvo s80, 2.9 auto tranny, avg 25 mpg.

- How are you trying to drive (e.g. trying to stay in electric only?) and how hard are you braking? mixed hybrid gas electric some EV.

- Are you "warming up" the ICE (internal combustion engine) by letting it idle after powering on? nope

- Are you driving using D or B mode? D

- HVAC settings? Are you using the heater, AC, auto mode, etc.? If using auto, what temp is it set to? lowest to middle setting, just enough to not get to hot.

- If reporting a mileage drop, did anything significant change on your car (e.g. accident, hit a curb or big pothole throwing off alignment, oil change/other maintenance/repairs, changed tires or wheels, etc.) or your commute? nope

Read more: http://priuschat.com/threads/fuel-economy-complaints-queries-please-copy-paste-answer-these-questions-esp-if-youre-new.77075/#ixzz32q6uRtlk
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Thats the thing, its running 5w-30 oil, and I'm actually having to try to achieve my mid to low 40's. i can hop in my sisters Prius and get 50 without even trying. in some sense i am a hypermiler.

Hey could somebody tell me some of the cheapest and decent LRR tires? (and how much they cost) I don't know much about tires. Do tire places ever trade used tires? plus i think my tires are almost new.

 

Thank you! i think ill give that a shot

 

Good idea. I think I'll pump up the tires a bit before I hit the road next week. I will also be crossing a mountain on my way to Georgia, it will probably drain my battery to the lowest level. Kinda excited!

 

I'd like to put in some bridgestone ecopias but i don't have the money thats what my sisters Prius has.

 

For some reason my prius has louder than normal exhaust, it sounds like the muffler is bad. I've checked for rust or leaks but didn't find any.
maybe in the next few weeks i will take it to an exhaust shop.

 

Okay guys, I made it to savannah Georgia. 4 guys, 4 suit cases, 2 backpacks, 1 beach chair, 43.4 MPG. Pretty happy with that number! The odd thing was, for the first hour and a half I only got 38, but after a couple of hours my mpg started rising. Idk

 

Yesterday I made the trip home, first tank 39 mpg, second average (the last 150 miles) 42 mpg

 

So yesterday i changed the oil in our two (Prii?), and mine (the one that gets lower interstate MPG) when you take the oil cap off, smoke comes flowing out...? the other prius has just a tiny bit of smoke, if any.

So what does this mean? bad pvc valve? do theses cars even have one of those? Btw my engine runs very smooth and quiet. I change my oil ever 3500-4000 miles. car has 228,164 miles. Thank you!

 

From what I've read online, most people say that means i need to rebuild engine? my engine runs great and doesn't hardly consume oil. Btw the engine wasn't all the way warmed up at the time of oil change