Same Prius, Not The Same MPG

Start with:

• what are tire pressures?
• what are engine oil levels?
• was fuel - same brand, 87 octane?
• was cruise control speed used?
• wheel alignment? (requires a fee)
• weather effects - temperature, wind?

Your indicated MPG suggests speeds above 70 mph, closer to 75-80 mph. At these speeds, small changes can make significant changes in the indicated MPG.

Bob Wilson

 

And to verify the obvious --
Parking brake fully released?
Brakes not dragging excessively? (compare brake disc temperatures)

 

Good, one item checked off.

That's not the question. What is the oil level on the dipstick in each? What you've said is effectively, "I don't know."

If they aren't from the same station then you have a difference. 87 octane can be very different from one place to another.

Doesn't mean anything. They don't drive the same because yours doesn't glide well. Have the alignment checked (you get a free one in the first year.)

Not at all definite. Possible, especially with such a large difference, but far from definite this early. See the above for a sampling.

 

drove both in same mode?? not a lot of difference between ECO or PWR but if doing a lot of small grade changes, i think it will affect your mileage.

i suspect oil level overfill and alignment.

 

Alignment can be off and the handling won't seem different. As a suggestion, if you have one of those non-contact IR temperature readers, you might take a drive and then scan for 'hot spots.' A brake would be easy to detect but it could also show up as uneven tire heat.

Sounds like an interesting puzzle. Please share whatever is found.

Thanks,
Bob Wilson

 

I mentioned dragging brakes due to first hand experience. When I had this problem on a long-ago domestic, caused by a shop who claimed it was normal up until the moment the wheels began smoking, a thermometer was unnecessary. The IR radiating off the discs could be felt several inches away, and the hubs were very noticeably warm to the touch. The discs themselves were too hot to touch for even an instant.

 

next time drive the exact same route, by taking it on the highway and set the cruise at the exact same speed (there is less variation for time of day with highway driving). I haven't driven the gen. III yet, but I can tell you that there are times when I can make my 25 mile trip to work at 75 MPG and other times I am struggling to make 52 MPG based on variations such as the ones mentioned above or current traffic patterns. (same car with no changes)
In your case I am still betting on it being either Climate control use (there can be a large difference in usage just from it being sunny or cloudy), tire pressure, or type of gas. If they rotated your tires they most likely lowered your TP be sure to check only after the tires haven't been driven on in at least 3 hours.

 

Not to put too sharp of a point on it, but you don't sound very serious about solving this problem. Many good suggestions have been made, but mostly you have dismissed them out of hand, often citing false information. If you don't want help, why post?

Tom

 

Just to eliminate another variable, why don't you have your sister drive each car doing the same route. You are bringing an expectation to the situation. Your sister may not. If she gets the same results that you do, it may help convince your dealer to investigate further.

 

WHEEL bearings?

 

I didn't see you confirm if the parking brake is depressed. As you may be aware, it locks at different level depending on how far you push. Make sure you kick it in all the way and another time to bring the pedal all the way back.

You may not notice wheel misalignment until you see tire wear unevenly over 10k miles. It may drive fine to you initially.

Why not do a simple test? Have both cars on a slight incline and then put both of them in neutral. Let them roll down and measure the distances traveled. It would be better if the same driver perform in both cars. This test will isolate the wheel alignment ,brakes or bearing.

 

Still would be worth checking.

While I doubt it as well, it is best to eliminate it. To eliminate it, find out where she is getting her gas and try to get your next tank there. I've noticed differences in mileage with different brands of gas.

I'm pretty sure you've got that wrong. I've never had a vehicle that lacked toe-in adjustment. And I've had vehicles that tracked straight, but with horrible toe problems.

As far as the rear, just because it is not adjustable doesn't mean that it isn't a problem. Rear alignment problems were an issue on the GenII and weren't adjustable without a special shim kit.

Time for a new dealer. At least half the Toyota dealerships I've dealt with really sucked. Since the one you've chosen falls under this category it would be best to try another that actually wants to solve the problem.

Actually, nobody has said they are all identical and perform identically. Instead folks have tried to point out things that you can rule out. I suspect there is something wrong with the vehicle and only so much of it can be tested by the user. But your approach is unlikely to get you anywhere.

Tom said it best:

 

definitely interested in what you find out. any chance of trading cars with your sis for like a week? you may think you are doing everything the same, but simply does not work that way.

my commute is pretty much consistent. afternoons not so much, but morning is pretty much the same. i easily have 10 mpg swings. granted shorter commutes introduce greater variances caused by temperature and SOC....ya, SOC, if your drive is short enough, starting off with low SOC can kick your mileage down a few notches as well

 

I have seen and read enough. You have proven to me that you Prius is working harder than you sisters to maintain 65 mph. Yes, it could be some of the factors that others have listed. I would think the dealer/service should be able to help with these kind of facts. If not - try another dealer, even if you have to drive a few miles. One would think they would have the correct tools to discover a mechanical problem.

Good luck - I am watching to see a solution.

--Mickey

 

Another way is to drive right behind and or beside of your sister for ten miles or so, of course the fuel consumption should be the same.
I'm betting that for some reason your traction battery isn't connected well or something similar and your using the ICE more often than you should, pure theory, based on nothing, but connections especially grounds are easy to clean / check