does your mpg keep changing constantly? I dont know if i can trust my numbers or not.

I reset and got 23 mpg on I-95 but once i got off the freeway, it went down to 17. The next day while warming up the car while idle (for 10mins), it went from 17mpg to 11mpg.

So idk if thats supposed to happen or not.

Also, ill mention on a full tank on the 99 rx300, ill get about 180miles.

 

I'm going to assume that you are talking about the average mpg, not the instant mpg. As only the avg mpg would make sense in this case...

Once you reset the avg mpg, the number's will vary for quite a while, as the computer is gathering data and averaging it all out. The more you drive, the more data it collects, and the more accurate the read-out will be.

So, if you reset it and drive for 5 mins. Let's say it reads 18. And, then turn the car off, come back and start it up. Leave it running for 10 mins (as you did), it's likely the mpg will drop drastically. Because, the computer doesn't have much fuel consumption data so this idling period will have a significant affect on your average mpg. < i hope what I wrote, makes sense to you... LOL I don't know how to word it better.

But, in other words, yes it's supposed to happen. haha

 

Well-put, hypervish.

Averages work this way. The fewer data points there are, the larger the variance as new ones are introduced.

 

Makes much better sense now, i have a tendency of resetting it each time i fill up my tank. Thanks hyper!

 

Are you really only getting 180 miles to a tankful? Sounds awfully low...even if you are in rush hour traffic all of the time.

 

We seem to average 16.9 mpg in mostly in-town driving -- lower than I'd like, but it seems to be in line with what people are getting.