I recently finisheda 7 day family road trip that totaled over 1600 miles. The bulk of these miles were pure highway miles of 350-500 (6-12 hour stretchs of time) miles at a time. I was curious to see how efficient my gas mileage could be. To be as efficient as possible, I used:
* regular gasoline
* cruise control
* tried to average 55-65 mph.
*used the AC sparingly, I had the thermostat set 75-77 degees when necessary

Even with these settings, I was expecting, at best, 35mpg. So imagine my delight/shock when I saw my "Tank Avg" climb to 41.5 MPG, on my 4-cyl 2007 Camry XLE. I thought this was a fluke. So I was shocked to get greater than 39 mpg during a number of other intervals during this trip. I was ecstatic to get these results but now I'm wondering how accurate these readings really are.

I noticed that my MPG really start to increase at the sweet spot of 45 MPH, during a stretch of highway construction miles. In this construction zone, I traveled for about 5-10 minutes at 45 MPH and I saw my MPG quickly climb to nearly 42 MPG. In fact, my results indicate the 45-55 MPH is best to acheive peak MPG. I think Consumer Reports recently reported this as well.

So how accurate is Tank Avg reading? Is it reliable? Do the rest of you get highway MPG like this?

Thanks.

 

Looks like my MPG weren't a fluke:
http://www.consumerreports.org/cro/c...-406/index.htm

Consumer Reports confirms my finds. I'm happy.

 

Actually, I've got a 1998 4-cyl that obtains very similar mileages at similar speeds. You are right in your definition of the sweet spot being 45-55 mph. This is true on most vehicles, including my 2001 Sienna which achieves its greatest fuel efficiency at 45-48 mph, likely because of its taller profile leading to greater wind resistance.

 

Regarding accuracy of your onboard computer...they are quite accurate.

My dad bought a 2007 Camry hybrid last summer. I have personally driven it on several occasions, including a 2000 mile road trip (round-trip total). The onboard computer estimates were allwithin 2/10 of a mpg every time we manually calculated mpg.

 

I'm thinking to prove out the computer that you should do a tank to tank manual calculation for several tanks. The computer also puts the coasting mileage in there, so I don't know how it calculates the "average".

 

Sweet spots for a lot of cars is at 45-55 due to good crusing speed and decent mix of wind resistance.
Toyota's have traditionally had more exaggerated MPG readings (giving you 1 to 2 more MPG than you actually are getting), but they're generally pretty on the dot.

Now if we could all drive 45, windows up, no fan/ac or other electronics and lighten the car, super inflate the tires, im surea bunch of us could get 30+ mpg. hehe.

 

I should add while driving in an is250, it's sweet spot was about 50mph. The live mpg meter was reading 40. haha.

 

I currently drive a 2012 SE 2.5 L Camry. Recently, I drove about 250 miles at close to 60 mph. The computer read out 39.9 mpg. It was climbing consistently, and I know would have done better with a few more miles driven. However, I checked it manually once before, and the computer was about 1-2 mpg higher than I calculated. I have owned a Chevrolet Malibu and a 2010 Camry, both with MPG computers. Each of them was 1-2 mpg over my calculations on a regular basis. I try to stop pumping gas when the pump shuts off automatically, so the fillings are relatively consistent. I discussed this and other factors with an on-line moderator at CR, and he discounted such things as temperature and how high the pump's pouring pressure was (differing pressures would make a difference in its automatic shut-off, and temperature would make a difference in fuel expansion, but he wouldn't agree that it was a factor). Nevertheless, anything causing us to be aware of our driving habits in relationship to the cost of driving is a good thing. Perfect accuracy is not necessary if we are caused to do the right thing by the info we get.

I traded a 2011 Hyundai Sonata LTD 2.4 L for this car. According to the computer, it got 41.2 and 42.1 mpg on several occasions. I think that my Camry will at least equal that. Some trade offs here due to amenities galore in the Hyundai, but I'm happy, and enjoy being back in a Camry.

By the way, it seems to me that the digital and the analogue needle meters are redundant. I would like for the analogue to suggest the current at-the-moment economy of my driving rather than the average mpg.