While on a level, smooth highway, no wind, A/C and cruise off, and keeping the throttle and speed steady, my trip computer's average miles per gallon fluctuates like crazy. The trip average appears to be reading correctly though. The last vehicle I was in outfitted with a factory trip computer, other than US made vehicles, was a 1983 BMW 833i. While driving it under the same circumstances as above, I don't remember it ever fluctuating, making it actually useful. My dealer told me that it fluctuates when under load, acceleration, letting up on the throttle..etc...................even though I would give him the above driving scenario. He appeared oblivious so I will ask a tech in the future next time I'm at service. Does your trip computer read as mine does?


Breakwater blue/RX-330 AWD/1100 miles so far

 

fat,

If it fluctuates a lot, it must be broken. I'm sure you double-checked the "Info" button setting, that is, when it is set to MPG "AVG", that should be a very steady reading especially after driving a half hour or so. If you are set to MPG only (not avg.), then it will fluctuate widely as you describe as it is calculating the fuel rate and speed to produce an instantaneous miles per gallon rate every 4-5 sec.

 

I'm sorry, it is the miles per gallon setting. Like I was saying, if at any time I want to know my current mpg so I can cruise at the most effecient speed, this fluctuating reading is lousy. With all that I did as posted before to allow the computer to not have to worry about any type of flutuating load as in up or down hill, A/C compressor going on or off, no wind, cruise control on, it fluctuates far far too much to be useful.

 

I think you have a problem. Mine stays steady after a few miles.

 

I have noticed exactly the same thing and find it useless.

Tom