My Tacoma does not efficiently do 75+ on the highway

Just drove from MD to TX, and after you get into the middle of VA the speed limit jumps to 70 for most of the drive, so I ended up doing 75 to 80 miles per hour, and was getting 17.5 miles per gallon using 87 octane and keeping my foot steady, no racing, just constant speed on long stretches of highway. I have gotten 20 MPG on some shorter trips with similar amounts of people/stuff in my truck, only difference was it was east coast driving so spent most of the trip at 65 to 70 miles per hour. I drive smooth and my wife and I switched off driving, and actually started a contest to see who could get the best MPGs on our trip, and she got 17.4 and I got 17.2 to 17.6, and we made a huge point to hyper mile and not stomp on it, I have managed 34 MPG on this trip with my old Pontiac G6 and it had an EPA rating of 30, you could do 85 MPH in that thing still get 30 to 34 MPG on the highway.

I have 100k miles, and changed my oil, installed a CAI, changed my diff and trans fluids, ran it in 2WD the entire time (DUH), and changed the spark plugs recently. Everything is running smooth, wondering if others have experienced such drops in MPG when going faster, didn't think this would happen and was a little upset once I started calculating my MPGs.

Also wondering if there is a maintenance interval on O2 sensors, or a way to test them? If I am running original ones, I figure they may have degraded and getting my MPGs up without dropping my speed is what I am looking for.

May just be the result of owning a truck and the greater wind resistance of a truck at these speeds...

 

Seems normal...higher speed=higher rpm which means more fuel burning...I've found these trucks get the best highway mpg going like 62-63mph. And anything over like 66 and the fuel economy goes way down..just my .02

EDIT: but yeah it's also a truck

 

shouldnt be speeding

 

best MPG for my first gen is right at 55mph in top gear. Any faster and the MPG's drop.

 

I don't understand all these people being surprised at high-teens real-world mileage in these trucks...

 

I have an AC and avg 16.8 according to Ultra Gauge. So your feathery foot has me beat, at least you something to build on.

 

I've been getting 18.5 consistently for the bast 4 weeks. My trucks bone stock, driving like a grany at 55 to 60 on the highway. And 95% of my driving is smooth moving hw

 

In general, sedans and cars will do better with mpg's at higher speeds because of the aerodynamic drag being so much less, due to the shape of the vehicle. Your Taco essentially has the aerodynamics of a brick, so higher speeds will make the drag your Tacoma work harder and harder to compensate for the wind resistance as your speed goes up. Same reason a v8 corvette can get 30+mpg on the highway if your nice to the gas peddle. It's all drag.

 

At that speed I'll usually drop to the 15 - 16 MPG range. I get the best mileage on the highway around 60 - 65 MPH. Once the RPMs climb and there's more wind resistance, MPGs drop. If those 2 - 3 MPG is a great concern, slow down... otherwise

 

That's about what I got on 2 2000 mile road trips from Cali to northern Idaho and back. I would echo the other posters is saying things dramatically worsen past 65mph. Your g6 was designed partly in a wind tunnel. My truck empty with two guys weighs 5000lbs, a lot more than your g6. I run a K&N 63 series CAI and it screwed up the MAF readings going to the ECU and the ECU was dumping more fuel than the truck really needed, Gadget over at URD sent me a MAF Calibrator which i installed into the ECU harness and this corrected the problem for the most part. Also, if you haven't taken off the throttle body and completely cleaned it you should do so, clean the MAF sensor too, I just did it and after I reset the ECU I have noticed the truck's idle is lower and it's running smoother.
Past that, there's isn't a whole lot left to do except slow down.

 

That is what you can expect from a Tacoma, on longer trips I can barely get 20 mpg, if I keep it easy on the gas pedal. I try to keep the tach at 2000rpms and below, to be the most efficient.

 

Sweet spot for me is about 65'ish.. That gets me a good solid 19-20mpg's.. Anything over and I get about 15-16mpg's.

 

Try a higher octane. I have never. Not really saying that much will change, but the chance is there.

I say that in part because a friend of mine recently installed an intake on his car. Actually dropped a few miles per gallon. However, when he bumped up one level of octane, he picked up an average of 3-4 MPG. No specific stations, no specific driving style. Just driving.

So with reference to that scenario, it is possible that you could pick up another gallon or so.

I do know something that will help. The NST intake manifold spacer. That alone will net you, on the low side, 1-2 MPG gain. Proven by many. As well as a small increase in hp and tq. Win win with that mod.

 

Wish i got that good...

 

I just got 18.7 mpg all highway @ 75-80 mph with 6 speed. my trucks stock with a camper shell.

 

I know wtf my stupid 1st gen gets like 10 mpgs

 

Three times a week, I drive 116 miles round trip to my office, just myself. 70% is highway(fairly flat) and the rest is on country roads(50mph). My average highway speed is between 65-70mph and I get 22mpg. I have a TRD drop-in AF, tires inflated to 34psi(front and back) and mostly gas up at the Costco across the street. If I drive 70-75mph, my mileage drops just under 20mpg. The truck has 12k miles so far.

I plan on replacing my muffler with a Borla Turbo XL. I'll update once I get a few round trips with it installed.

 

Drag increases with the square of velocity. So if you go twice as fast, drag is increased by a factor of FOUR!

So yes, if you go faster... you'll get less gas mileage.