Slowly losing MPG

Test the 12 V battery again.
If it is over 5 years old, replace it.
Just because.

Then don't do anything drastic (expensive) until they stop selling "winter blend" gas.
Your mileage might go back up a bit.
Oh, and also check the air in the tires.

 

maybe injector cleaner, throttle body/maf, egr/intake manifold cleaning.

 

Asked and answered--it's the tires--go back to decent LRR tires, and keep the pressures up.

 

One thing to consider in the Gen3 is the egr circuit .

At 176 k miles out 2010 just got round #2 of egr cooler replacement and circuit cleaning. I was getting 48 mpg prior to this work.

After the cleaning, I am up over 51 mpg with the same travel pattern back and forth to work.

At your mileage, I’d start to think about cleaning the egr circuit for various reasons.

Keep us posted .

 

Yep..your car is at the point where all of this extended maintenance stuff needs to be done.

Check out the "nutzaboutboltz" maintenance videos here :

Nutz About Bolts Prius Maintenance Videos | PriusChat

They have helped many of us tremendously!

 

For that you might buy some used motor parts, clean them, and have your mechanic swap the parts. That would be a lot less down time.

Pixel XL ?

 

I've only done it once. It took me the majority of two days. But I did extra: installed a screen over the vent duct, spark plugs, changed transmission fluid, etc. An experienced mechanic might take 6-8 hours to swap parts.

Pixel XL ?

 

Wow, the estimated price to have a mechanic do the cleaning would be in the neighborhood of 6-8 hours? This is more expensive than I originally thought.

 

That’s assuming the mechanic will even tackle it.

So expect high prices.

 

That estimate is just for swapping parts. The removal & replacement of the window cowl is up to 2 hours by itself.

How much more time will they charge for cleaning parts. Don't know any mechanics that clean. Will they do a thorough job? Or just half a$$ it IDK.

That's why we try to persuade PCers to clean used parts themselves to avoid engine damage

Pixel XL ?

 

So if what I'm reading is correct, since the baseline of 41 mpg after replacing the tires, the MPG only dropped 1 mpg?

Well, I think all the maintenance and cleaning suggestions are great. Probably needed in any case. And doing them will probably help raise your MPG's.

But from reading the post, it seems like the major drop happened after changing to non-LRR tires.
So I don't know what to advise. Hopefully doing everything else, will raise your MPG to a level you find acceptable. But the biggest drop in your MPG came after replacing the tires.

 

So pump the tires up to 45lbs, and....the brakes need service, cleaning and greasing the caliper pins will add mpg's, any bearing noise?
Trickle charge the 12v so it's charged, make sure the emergency brake isn't at all involved, and replace the cabin air filter.

 

Need to change fuel injectors

 

You better clean the EGR circuit soon, your mileage drop is your car’s way of telling you it is sick.

If you fail to clean the circuit you will be wishing you could have your poor mileage back when you see the head gasket repair bill.

I wouldn’t trust a mechanic to do the cleaning unless they were experienced with Gen 3 EGR problems or replacing with a new EGR cooler. The reality of cleaning the cooler is that it is not something that can be done quickly. You have to soak them, hit them with pressure washer and soak again and again. Search the threads, clogged EGR is the Prius Gen 3 cancer.

 

Couple of threads, outlining the issues, and with fixes:

EGR & Intake Manifold Clean Results | PriusChat

Oil Catch Can, Eliminate that knock! | PriusChat

Also of interest, in particular to show how long this bs has been going on:

Prius 2010 Engine Knock - Manifold Issue | PriusChat

And older:

Prius III engine knocking at high torque low RPM (solved) | PriusChat