Scottmt77

Hi, we have a '15 RC 350 (not the F) that has been getting extremely low mpg. The car has 10,000+ miles. Lexus Service manager at our local dealership said that he can check the current mpg manually but HAS NO WAY TO GET A MPG HISTORY OF THE VEHICLE, even though the onboard computer was working fine, continually showed us it was recording both mpg and range left until empty. We would often reset the mpg tracker when filling up so we got repeated data points of mpg. QUESTION: Does anyone know if the onboard computer records the full history of mpg on a vehicle or not and if so, do you know how we can access this data? Thank you!

lobuxracer

iTrader: (2)

No, the ECM doesn't store that data. Also the data displayed on the dash is not accurate, it is an approximation based on a single injector's duty cycle and can be fooled many ways. I wouldn't waste a lot of time with this.

Scottmt77

update, ended up talking to Lexus customer service who stated the data is stored from mile 1, shows repeated average data based on reset (such as best average fuel economy) and easily retrievable as shown within Owners Manual around page 128, Instrument gage section.

lobuxracer

iTrader: (2)

Or battery disconnect. It's not stored they way DTCs are and it's not stored in the ECM, it's in the combination meter, and easily altered, tampered with, or reset as well as inaccurate. I've done a whole lot of comparisons between the displayed mileage and the actual calculated mileage. It's really just there to make you feel good.

grandspt

I have the RC300 F-Sport and mileage is not great. Winter time I average about 16 to 17 MPG city/highway combined. I notice when I have my climate control off (no AC) I can get 18-20MPG. So I believe that there is a large drag/power consumption off the AC compressor.