can i get 60mpg without any mods?

Adding weight to the car will not increase your MPG. It will drop it. I would check your parameters before conducting calculations. There are A LOT of variables that most people never take into consideration when evaluating MPG including: road surfaces, wind speed and direction, density altitude, temperature, driving distance and pattern changes, fluctuations in MFD displayed MPG, etc..

 

I just put on Michelin Energy Saver A/S and my mileage immediately jumped up a couple mpgs. The Energy Savers are obviously designed for fuel efficiency, but it was nice there's no waiting period to see the results with those tires. I even went from 40/38 on the original Integritys down to 38/36 on the Michelins. I'll probably bump it up now that winter's fast approaching and I'll need every bit of help I can get.

 

Unless the back shocks were replaced but not the front ones, then the car might be scooting around with its back end up in the air, and putting a load back there would even out the car again for better aerodynamics. Not the normal case I know, but it's a possibility.

 

i have driven 180 miles on motorway this week at 70mph. combined with approx 20 miles in town. I have averaged 61 mpg. last week doing the same trip i achieved 55mpg. What i have noticed is it is better to get to your cruise speed quick then ease off the gas rather than accelerate slowly - this just prolongs the increased consumption for longer. I have also noticed that the trip computer over calculates by 10 percent. so if your computer says you have averaged 55 mpg then really it is 50 mpg.

 

Rarely, really rarely above 58 mpg. More like 55 mixed if you drive nice. 60mph 60 degrees about fits it on cruise. New tires make it worse and I've tried several types on my 5 prii. Really hot or really cold outside makes it dip to 45-48 mpg. Gasoline type or octane or additive makes little difference. MPG chips/Power modules make little difference so I took it off because it does other funky things. I find going 60 or 70 on cruise freeway makes little difference in overall mpg.

 

I can only get 60 MPG if I limit the speed to not much over 50MPH (maybe 55). Over that and it drops pretty steadily with speed. At 70MPH it's usually down to about 50MPG (probably lucky to keep it above 50MPG actually).

 

I don't think worn shocks will change the ride height of the car since they do not hold the car up. The springs do. They could cause the front to ride high for very brief periods when going over big bumps on the highway though.

 

everyone says rear tire pressure 2 less than the front,
front 42
rear 40
or 38/36
but why?? i have my tires all at 42, what is so wront with that?
is it just for ride comfort?, proper ride height aerodynamically?
maintain good traction in cornering?
or just because the OEM recomneded pressure is offset by 2 psi?

 

All 42 wont really be a problem. The reason for slightly more pressure in the front is because that's where most of the weight is.