How to improve MPG in my 2002

New tires may help. I currently have General Altimax RT43 installed. Several of us old-timers with the Classic keep the inflation pressure at 44 psi all around (alternatively, 44 psi front, 42 psi rear). When I venture out on the highway, I try not to exceed 60 mph. That will improve mileage too, especially in cruise. OE tires on the Classic were XL (extra-load), and the recommended pressures were something like 35 psi. I have not run XL tires on my '02 in many years, and I always inflate to 44 psi. YMMV!

 

First I'd wonder about how many trips/miles/tanks of gas or whatever your calcs were based on. But mostly, I'll just say that if most of your regular commute is 65-ish highway miles on cruise, then mid to low-40's-ish is about right. You won't get 50s+ mpg on the highway, so if that's what you thought you were getting in your previous Gen 1 it was quite likely an erroneous number in one way or another. If you want 50-ish keep it at 55 and under and stay off the accel pedal as much as possible. The cruise control isn't very good at that, btw. They're basically "dumb" devices that only read speed.

 

I did recorded my gen1 for many years, here is graph it is in litres per 100km so it is in reverse to MPG, lower is better, best was 43MPGus 51MPGuk, average 36MPGus 43MPGuk and worst 26MPGus 30MPGuk bit I think it is refill data inaccuracy as I never got that bad. Data is for UK prius with several international trips.

 

going downhill a lot helps too. But yeah, ditto. All mine have averaged in the low 40s. Except in the summer here in Houston, in city traffic, when the engine never cuts off while idling to keep the AC going. My dash gauge goes down to the low 30s then, over several hundred miles of averaging.

 

My '02s AC works with the engine off, stays cold for about 20-30 seconds and the engine stays off for about 1 minute, even at 90 degrees ambient with the auto climate set at 75.

 

Maybe the compressor stops, I haven't noticed, but the fan keeps running, and my MPG goes way down. Some of the traffic signals are several minutes long.

 

You can raise the rear and confirm the back wheels are near-freely spinning. Long shot, but good to check. With the fronts connected to the drivetrain it's not really possible to check them. But a four-corner brake service might turn something up.