drop in mpg

Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new | PriusChat

 

Are all of your tires up? Have any leaked down?

 

Obviously, air conditioning use will reduce mileage a little. Cooling the cabin less (with a higher target temperature) will be more economical than maintaining a colder temp.

I don't know about the Prius c, but in the hatchback by selecting ECO mode the A/C is operated in a less demanding way.

 

If you want help, please answer the questionnaire.

As for don't have a gauge, buy a quality one. Do NOT depend on notoriously inaccurate gauges on air hoses at gas stations. You have no idea what condition they're in.

 

a drop that large can't be anything minor. test your 12 volt battery. does the car seem to be running any differently? how about the behavior of the hybrid battery gauge?

 

First, is the car in tune? spark plugs, air filters, coil packs, and timing? you need to have a diagnostic check on the car to identify any deficiencies. Most aftermarket parts stores will perform the check for free. It involves plugging a reader into the plug on your car and waiting for interrogation results.
Tire pressures are a potential problem; make sure you have 35 psi front, 32 psig rear. And make sure you replace the air filter just in case. And its possible your oil filter is plugged if its been long time since it was replaced. Itsd small and if you've been driving in dusty areas could easily be filled with contaminants.
First on the list of suspects is the air filter. Even a little contamination will seriously increase the pressure drop across the filter and that adds considerable effort that the engine must overcome by using more power, hence less mpg.
And check your emergency brake to see it's releasing fully. Its a common reason for reduced mpg too. When fully released the car should easily be pushed on lecvel,ground, making sure it doesn't get away from you. If its not easy, then recheck to see the brake lever is fully off. And then if the adjustment is correct. If thats OK we get to more serious stuff: its unusual but occasionally we see a brake caliper or drum cylinder 'frozen' such that the piston or shoe is 'frozen' against the rotor or drum. Adjustment is likely not your correction unless you're a confirmed DIYer; RNR the cylinder or piston is pretty much a good mechanic's job.

 

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You SERIOUSLY think that there could be a problem w/the spark plugs on '13 Prius c? The spark plug change interval on my Gen 2 Prius is somewhere past 100K miles. I'm still on my original plugs after 70K miles and over 7 years. The timing can't easily be adjusted. It's all computer controlled anyway and changes all over the place (looking at IGN values on ScanGauge II) depending on MANY factors.

Replacing an AIR filter at this point? OIL filter? OCI should be 12 months/12K miles.

Anyway, OP will need to answer our questions.

 

This is weird... should be you are getting higher mileage with the warmer weather, not worse. Even with AC on full blast for over 50 miles, I can get better mileage on the highway than winter time.

 

Check to make sure that your vent in the rear driver side foot space isn't covered. This will drop MPGs significantly.

 

Have you trips gotten considerably shorter than before? 5 mile trips are pretty short and that'll yield a lot worse mileage than 20 mile trips, if everything else is equal.

 

You should never be getting anything near 20-30 mpg unless you're in an awful traffic jam with the AC on, are driving 100mph, make only very short trips, or drive like a complete idiot. You'd really have to try to make a normally-functioning c be that awful.

I'd recommend taking the car back to the dealer to do a check-up. They'll be able to do a physical check-up better than we could.

 

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What are the results of your (cold) tire pressure check? And, what about the trip length change question?

 

Be sure to keep us updated!

 

Did you check the back seat vent? Another poster on here had a drastic drop because a plastic bag was covering the hole. It wouldn't let the battery engage for a significant period of time, causing awful mileage.