How can I improve MPG on highway in new car?

How can I improve my MPG on the highway? Window sticker said 28 on hwy - I get 19.6 - using cruise and going 65 MPH. 2007 Lucerne - purchased Nov. 2008 -

The only way to improve you gas mileage measurably is to slow down, don’t use the air conditioner and inflate the tires another 5 lbs. The slowing down is the most effective. The EPA mileage is measured with the car stationary, going slower than 65 mph and all accessories off. That’s not real mileage, and is to used for comparison purposes only.

To start from scratch, carefully measure the mileage over a 3 tank period. Tank gas at the same pump, same nozzle, and stop at the first click!

Using the cruise will only save you mileage on a flat highway with light traffic. Under normal driving, just pretend you have an egg between your foot and the gas pedal. Use the brakes lightly, and drive as smooth as you can.

19.6 mpg is not great, and some improvement is possible. But if you want a really significant improvement, you should drive a smaller and lighter car.

Is it really all highway/interstate driving, or is it mixed with some start/stop city type driving?

The suggestions by Docnick are valid. Yet, your mpg is just under 10 mpg less than the EPA posted figure. This seems much too big a gap. I wonder if there is a mechanical “drag” somewhere in the brakes or drivetrain.

Assuming your methods in calculating the hwy mpg is correct, something is amiss.

Check your tire pressure and slow down to 59 mph, no cruise. Try it and post back. Rocketman

That does sound low, only things I can think of:
-Assume you’re talking 100% highway
-Assume you’re calculating mpgs, correctly (see Docnick’s post)
-Assume you’re measuring tire pressure first thing in the morning, no driving, with a quality (dial) tire gauge
-Are your tires wearing evenly? Have your Buick dealer check the alignment, that could cost mpgs
-Check that all fluids are at their correct level, especially the transmission
-Have Buick scan for codes

It seems to me there are a lot of blanks that need to be filled in.

The OP refers to this as a “new” car but it’s also an '07 that was purchased in Nov. '08.
This means it was either a used car purchase or one of those malingerers that just happened to be stuck on a dealer lot for an eternity. That’s rare.

If this car was sold new in '06 this means this vehicle could have been on the road for 2 years when the OP bought it; 3 years if you figure up to the current date.

So was this a brand new, 4 or 5 miles on it vehicle or what?
Even tossing that scenario aside, when was the last time the tire pressure was checked?

How about the Tappet Brother’s favorite answer? Bad coolant temp sensor. Should set a code I would think, but who knows?

It’s a remote possibility, but the odometer could be off and not registering the number of miles traveled correctly. If the odometer is slow, it could be registering fewer miles than the distance you have actually covered.

You might even check to make certain that the car has the correct size tires. There should be a plate on the left door pillar that gives the tire size–be certain that this is the size on the car. Years ago, I purchased a used 6 cylinder AMC Javelin that needed tires. I found one pair of good used tires that were oversize for the car. I then bought two new tires that were the same size as the oversize that I had purchased. On a trip out west, we were in the middle of Iowa when we stopped for gas. The car took a quart of oil which it had never done before. The gasoline mileage was less than 15 mpg. My wife calculated our average speed across Iowa–distance/time. We had averaged about 80 mph. I had never driven above 70 by the speedometer. I had been complaining that the engine was noisy and I almost had the accelerator floored to maintain this speed. It finally dawned on me what happened–we estimated that we had been traveling between 90-95 most of the time and the pool little 6 was running practically full throttle. When I backed off and drove at the speed limit, we averaged 24-25 mpg.

Exactly how did you measure that 19.6 mpg?

Cruise control can only increase MPG if the driver is over-controlling. What I mean is the driver is making more corrections than necessary. A good driver should be able to at least equal the CC for MPG, better drivers can best the CC by knowing when to let the car slow or gain speed on hills.

If CC improves your MPG then you need to spend some time in contemplation as to what you are doing with your right foot.

Over-controlling is a very common problem for new pilots.

If the terrain is hilly, the cruise control will over-orrect and dowshift the car to mainain the exact speed. This will use more gas than being very easy on the throttle, which will pevent downshifting.

I agree that a nervous, jerky driver will use more gas than a car on cruise control, hence my advice to feather the throttle.

First of all, I doubt that the window sticker said 28 MPH highway. 2008 was the first model year for the new method, and your car would have come from the factory with the new rating. If you check the EPA web site, the 2008 Lucerne was rated at 25 MPG with the 6-cyl and either 22 or 23 on the highway with the 8-cyl. It could be a 2009. Are you using E85? The 6-cyl flex fuel Lucerne is rated at 20 MPG hwy with E85; 26 MPG with E10. The 8-cyl is rated at 22 MPG. So, what engine do you have, and what fuel are you using?