How are you tracking your MPG?

I record and post my mileage at Hybrid Mileage Database - GreenHybrid.

Initially I was recording both the weekday and weekend mileage to get an idea about what different experiments. Later, after I got a Graham scanner and finished my fuel studies, I just fill with Shell 87 when it gets a little low.

Bob Wilson

 

Ditto. Only got 2 tanks recorded

 

I use the gas station receipts and one of the trip meters. BTW, if you pass over the "notes" on that 'large' tank, what happened is I forgot to reset the trip meter on one fill up. By the time I realized it, I had already put a bunch of miles on the car. So later when I filled up again, I just added the two receipts and trip meter mileage ... don't sweat the small stuff. <grins>

I prefer to use the MFD mileage display for experiments. So when I was testing hill climbing efficiency, I simply reset it at the beginning of each climb and recorded the MPG at the end for different speeds. Since the MFD miles is imprecise, I'll often clear one of the trip meters at the same time to get the distance to the nearest 1/10th mile.

GOOD LUCK!
Bob Wilson

 

i do it the old fashioned way... paper pencil... well actually, gas receipts and excel.. but same thing....

 

Bob I noticed from your millage post, the cars seem to get better mileage when the tempter is higher. Would you think it is the intake air for the ICE or because the oil is hotter and thiner with less resistance. Maybe the car needs a higher thermostat for better mileage. I think I will install a watter tempter and oil tempter gage and monitor them to see if higher tempter makes a difference in millage. Any thoughts on this. Thanks Roy

 

This remains an area of great interest and the more we look at the data, the more curious it becomes. Every winter I have learned one new thing but in North Alabama, our winters are short and mild. I'll summarize these lessons later ... not enough time for a full answer.

Welcome to the CLUB! Some of our Japanese friends have done some work in changing the coolant thermostat and I think Patrick Wong did something in this area.

Bob Wilson

 

better gas mileage in summer is result of several things:

summer gas has more energy. gas has a relatively high freezing point. to prevent gas line freeze ups, components are added to lower the freezing point. simply put, the components take up space but dont burn... hence a "gallon" of winter gas does not have a gallon of "gas" in it.

cold air is denser. denser air means the car has to work harder to get up and maintain speed.

warmed up cars get better mileage. your Pri, like any car with ICE runs best around 180-190º F. that means that those short trips you do in the summer can be up to 50% more efficient than the same trip in the dead of winter since in winter you will not get that high on trips shorter than a few miles. i ran several tests on my 2004 with CANVIEW and found that in the winter time, not only was getting the Pri warm took longer, i also had issues with keeping it warm if driving on surface streets at speeds 35 mph or less. on drives with frequent stops, i may lose 5-10º of engine temps just by sitting at stoplights. get a handful of those in a short stretch and i was seeing engine temps down to the 150's...iow, at the bottom of the warmup stage again.

defrost and A/C defrost is a killer on your mileage. its also something that is vital in certain areas (me for example since humidity is 99% EVERY winter morning here). unlike the AC in the Pri which is electric, highly efficient and evolved to reduce energy consumption, the defrost is not. barrring temps in the high 100's, The Pri's AC has a relatively small impact on mileage unlike the old belt driven compressor style AC of the past.

 

Some additional significant factors causing lower MPG in cold weather include:

1. Tire rolling resistance goes up as temperature goes down. True LRR tires mitigate this tendency by using organosilicates in the rubber compound to retain flexibility at colder temperatures.
2. Wet/slush/snow on the road surface significantly adds rolling resistance and is more prevalent in cold weather.

Attached is my current MPG spreadsheet (4 years, 118,000 miles). It clearly shows the correlation of MPG and Temperature as well as comparing two different true LRR tires (Michelin MXV4+, Nokian WR) with the original GY Integrity tires that came with my 2004 Prius.

JeffD

 

cold air is denser. denser air means the car has to work harder to get up and maintain speed.
Hi Dave, thanks for your info. I also had a thought on the cold air verses hot air. I know there is more oxygen in cold air than in hot air from my racing experience. Cooler, more oxygen, more power, go faster. I also thank there is more Ario drag on a car in cold weather, your term denser air. I don't have a clue as to how much. I think this would partly explainer the higher millage in warm weather. On the engine temperature, a race car makes the most power at about 220 degrees F., however I don't know if it is the most efficient. Any body know if the engine temperature can be monitored with a scan 2 code reader, as I would like to monitor the engine temperature.

Roy

 

Hi Roy,

I agree that the Prius mpg seems to improve in hot weather, frequently making up for the extra load imposed by the air conditioning system.

As Bob mentioned, I explored the feasibility of obtaining a higher temperature engine thermostat with Ken's (in Japan) help but this is not stocked by the US Toyota parts distribution system. I lost interest in that particular project with the seasonal return to warmer weather and the press of other activities.

Since you live in Florida I would not suggest using a higher temp thermostat unless you have a reliable way to track your engine coolant and engine oil temps.