My wife and I purchased our first Lexus in December, and we absolutely love the car.

The 2008 ES350 is rated at 27 MPG on the highway, and I was curious to see how the actual mileage would compare. Last week, we took our first road trip, traveling from Southern California to the mountains of Utah and back. We ended up driving 1678.3 miles, burning 61.423 gallons of gasoline, which gave us 27.3 MPG. Not bad!

However, I also tracked the trip using the car's computer, by zeroing everything out at the start. The computer showed the mileage to be better than what we actually got on every tank, and computed a trip total of 29.0, or 1.7 MPG better than we actually got. This means that the car's computer is about 6% too optimistic. I have seen posts where people are reporting that they are seeing 30 MPG with the ES350. If they are using the on-board computer, then the actual mileage may be less.

This is obviously not a huge problem, but it would be nice to be able to rely on the computed MPG. I will see if this can be calibrated when I take the car in for the first oil change. If an adjustment can be made, I will report back.

 

well it really depends of when your first fill up was, and how much you filled up your car after you came home. Although a couple of gallons probably wouldnt effect your numbers, but i usually fill up.. drive a distance, fill up again, then use that amount of gas that you filled up, to calculate the previous miles driven.. but im sure you did it that way anyways.

 

Thanks for the response. We started the trip with a full tank. I included the actual gallons from pump receipts for all subsequent fuel stops, ending with a fill-up at the end of the trip. I reset the on-board computer when I filled up the car at the start of the trip, and took the last reading at the fill-up at the end of the trip. If properly calibrated, the on-board computer should have come up with the same figure that I did, allowing for some slight variation in the beginning vs. ending fill-ups (you can always squeeze in a few more cents at the pump). A 6% error seems too high.

 

Boater, not bad at all! I got my ES in December and did a 200 mile trip with about 20 miles city included in that 200 miles (the rest was mainly on Interstates) and I got 33 mpg! I was ecstatic! My tank average ended up (with the rest in city driving) was 28.5 mpg. And this was the computer only. Not bad for a 272 hp V6!

 

My computer typically shows 34 mpg on the highway. The actual is between 32 and 33. Surprising yours is only 27. How fast were you driving?

And another thought, how much air do you keep in your tires? I make sure all mine are at 32 psi cold before hitting the highway.

 

My computer is about 1 mpg optimistic too.

For me that is good enough for quick day to day reference. If I want it exact, I figure things manually.

 

On four different vehicles I have owned the manufacturer's computer calculated mileage was overly optimistic. That's just the way they do it.

 

A couple of small--but perhaps not so insignificant--factors:

1) It is assumed that you're topping off at the exact same level at every fill-up; otherwise, how would you know for a fact that you're driving away w/ the exact same amount of gas after every fill-up? The only way you can know for sure as to exactly how much gas you pumped into the tank is if you filled it up when the tank was completely empty...and since that's not really a feasible option, you'd never really know for sure exactly how much is in the tank upon fill-up. Sure you'd say that when the gas nozzle clicks shut, that means your tank is full...however, this leads to factor #2...

2) One can't assume that the vapor recovery system--either that of the gas pump and/or in the vehicle itself--is always in perfect working order. What's to say that the pump nozzle doesn't click a wee bit prematurely? If you base your determination that the tank is full based solely on the nozzle clicking shut, then it can be possible that your tank isn't as full as you think it to be...if indeed there is an issue w/ the vapor recovery system.

Bottom line--unless there's a huge discrepancy between your manual calculations and what the computer is reporting, I wouldn't be too concerned if the computer readout is off a bit.

 

Not that I'm disputing your figures, but one needs to keep an open mind in that there are a lot of factors--some more obvious than others--that can affect fuel economy. Granted it's not a ES350, but FWIW I got 24 mpg out of my Yukon XL Denali (3-ton vehicle w/ a 6.0 liter engine) during an 80-mile drive, while averaging 65 mph during that stretch. Now I'm sure some of you folks will call BS, but I'm not lying. How did I do it? Simple--I was driving home from Truckee (CA) to Sacramento (for those of you who know the route, you can see how it was possible)...and I probably could have gotten 25-26 mpg had there not been pockets of slower traffic from all the folks heading home from the ski resorts on Presidents Day. The point is that, under the right or wrong conditions, one can achieve really great or not so great fuel economy figures respectively.

 

Good points there toneman, but all common sense.

I'm wondering why we have not heard back from boater. I'm calling BS on this one. 27 mpg on the highway?

 

i just bought it and i get 15 mpg!! maybe its because im flooring the car everywhere.

 

I live in the same area. I can see how it's done. It's like downhill coasting half the time. With nice scenery to watch until you hit the Roseville area.

 

Are you insinuating that he should have achieved better hwy fuel economy...or that he's being overly optimistic w/ that figure?