2.7L Mpg Testing

So I took my 17 2.7 auto (double cab 2wd) on a trip recently and was trying to achieve maximum hwy mpg, so I kept it at 55 mph during most of the trip, which has always yielded the best mpg for me with all my previous vehicles. After filling up, I was shocked to see the mpg achieved was only in the low 20s, which is about average for me and nowhere near my best tank.

This got me thinking and I decided to do a little mpg experiment to see what was going on. My wife just shook her head and got out the honey do list when I told her - I've obviously got too much time on my hands she says.

In any case I found a lightly traveled stretch of road (about 85%hwy and 15% city driving) near a gas station and traveled the same route over and over under a number of different speeds and at differing levels of acceleration (and did a few trips with/without the ECT button pressed to see how that affected things). I tried to keep it as scientific as possible - all the trips were done the same day under similar conditions - no wind/rain and mild temps.

Here's what I found: Best tank of gas was 27mpg, at 65mph with slow acceleration. The best tank I got at 55 mph was only 21mpg! I was shocked and still don't understand it - the rpms at 55 were below the rpms at 65 so it wasn't a case of gearing or the transmission upping the rpms at lower speeds. I really don't get it, but the result was clear.

Other interesting things to note - the sweet spot seems to be between 60-70mph, with mpg ranging from 24-27 with slow acceleration. At 75, mpg drops considerably to around 20. Also, even though my route was only about 15% city driving (so these are basically hwy conditions), as expected the slower the acceleration, the better the mpg, with numbers dropping 5-10% from slow-average acceleration and another 15% from average-fast acceleration.

Finally, driving with the ECT button engaged definitely brings up the rpms and makes driving more enjoyable especially around town so I was curious to see how it affected the mpg. It resulted in mpg decreasing in all scenarios, ranging from a 4-25% decrease.

I'm kind of a car nut/nerd (obviously) so this was all really interesting to me and practically speaking tells me there's really never any need to drive below 65mph if I'm trying to get the best mpg, which is great!

 

I have a 2017 2.7l extra cab, , Mileage SUCKS in all cases, because the motor is such a dog you have to lay on the pedal to get it moving

 

What are you calling slow acceleration? Is she shifting at 2k 2.5k 3k? I do a lot of back road riding n 55-60 can be flying at times. In a 4x4 I'm getting around 20-21. I have noticed a large difference between cold and warm weather mpg also

 

I think you are putting more load on your engine going only 55.

 

I do mostly hilly country driving. I drove like a grandma for the first 3 tanks and averaged 19mpg consistently. On this last tank I took a spirited drive up the coast and drove with abandon, partially in 4WH on a dirt road. I averaged 22mpg. I don't think the 4 banger benefits from conservative driving.

 

No mpg is worth going only 55...Good info though Thanx!

 

When I was testing under "slow" acceleration, I was trying to keep the RPMs under 2K. Which is really slow.

 

I don't see how, though. Engine speed is lower at 55 than 65. I can't think of what would be stressing the engine more at that speed vs. a higher speed

 

Engine is work harder to produce power at the lower RPMs.

 

This engine wants to live at higher revs. It can take it.

 

18.3 best average tank so far 3500 miles.i need to drive 75 to 80 mph on I 95 just to survive . gmc Sonoma with the 4.3 got 16 on same trips.26 mpg is a DREAM!!

 

Thanks for sharing OP, interesting observations. I'm averaging 22 in winter and 24 in summer. Doesn't really matter the ratio of city/hwy. Mostly 70 mph on hwy and short trips (3-4 mi) in town. My cruise can't hold 6th gear unless I have a tail wind, but without cruise I can hold 6th even with a slight headwind and incline.

Not to derail, but anybody notice that Toyota bumped the city mpg from 19 to 20 for the MY2018 2.7l?

 

I hadn't noticed that.

 

Wow, under 2k, it must have taken 5 miles to get up to speed

 

I would like to see a couple people reproduce these same results before I took it as gospel, but regardless interesting and thanks OP

 

My best ever was 23 MPG driving to the border. 16 miles of flat ass road.

 

Prius' get good mileage. I'd recommend looking at those of mileage is that important.

 

I'd love a 2000 Honda Insight as a daily. Used to commute in one. Got 75mpg.

 

Peak torque occurs at peak volumetric efficiency, the point at which the engine is moving the most air. At lower RPMs the engine could be suffering pumping losses, producing less torque, thus requiring you to put your foot in it a bit more to keep the desired speed which in turn drive fuel consumption. Driving a bit faster, with an engine rpm closer to peak torque/volumetric efficiency would be more efficient, requiring less fuel.