Coworker dropped average MPG by 2

how many miles was on that tank when you gave it to the coworker?

 

I think there is a simple answer.

First, I'm assuming your co-worker doesn't own their own prius and may have never driven one before.

Could it simply be, that if YOU are getting 48.7, that an untrained driver would likely get less? My average is right around 50 (after 4000 miles - 50mpg calculated both by MFD and fill ups). I would certainly expect that if someone else drove, it would likely drop.

Also - In that 40 miles - I assume they used it to go somewhere, right? Not just drive around for 40 miles? So, how long were they at their destination? That could be 2 warm up periods, which would also drop the mileage a bit.

Bottom line - there's lots of factors, but 2mpg doesn't seem that unusual. If it was 10, then I think you might have an argument.

 

Inside of 100 miles on a tank, even 4MPGs up or down over 2 miles is easy. Mine only settles into a solid average around 200 miles...

 

that would be very easily to drop 2mpg on a 50 mile tank. I mean you should be glad that it only dropped 2, really. It depends on many factors, stop and go traffic, how many warm ups he/she did, driving technique

 

With 50 miles on the tank, I can easily drop 2 mpg just during my 2 or 3 short trips during the work day, such as going out to pick up lunch and such. Even with 300 miles on the tank, I can drop 0.5 mpg during short trips at work. I usually gain it right back on the ride home.

I guessing that you commute to work in the morning and then your car just sits in the parking lot all day until you commute home at night.