6/3/2008

ES350 Gas Mileage. I had a chance to conduct a good gas mileage test because I had to drive from Las Vegas, Nevada to the mid San Francisco Bay area.

For this test I had 450 miles of freeway with 4 sizable up hill runs. Because of this I ran the test both ways first to the SF Bay area and returning to Las Vegas for a total of 900 miles. I burned mid-grade (89 octane) gas in our 2007 ES350. I used the Lexus computerized mileage meter on the dash board for the average mileage figures.

This test included only freeway driving 450 miles each way for a total of 900 miles. Both ways I drove at 75 to 77 MPH with a variance of anywhere from 62 to 80 MPH as the traffic dictated.

From Las Vegas to the SF Bay area the overall freeway only mileage was 30.5 MPG.

From the SF Bay area to Las Vegas area the overall freeway only mileage was 31.9 MPG.

Therefore the two way average was 31.2 for the 900 mile freeway only trip.

The difference between the two 30.5 versus 31.9 is probably because there were some significant up hill runs and a couple of long 40-50 mile slight up hill runs which of course become downhill runs in the other direction.

We learned long ago, in our motorhome, that the extra fuel used on an up hill run (lower MPG) is NOT completely recouped when you go back downhill in the other direction. In other words the downhill run gives better MPG but it does not make up for the lower MPG on the up hill run.

Personally I am pleased with this highway gas mileage.

JerFitz

 

Last week we returned from a 2,500 driving vacation. According to the car's trip computer, the overall average gas mileage for the trip was 30.0 mpg. The final "Tank Average" was 32.9 mpg. The trip was mainly highway driving, with some non-congested city driving along the way. I usually drive 65-75 (maybe 80 in spots) mph depending on traffic.

I've been using 87 octane regular unleaded for about a year and a half.

I didn't figure the mileage manually, but when I've done it in the past, the car's computer is usually about 1 mpg higher than the manual figure.

I too am satisfied with the mileage and performance of the ES350.

 

Drove from Wilkes Barre, PA to Cleveland today, averaging 72-75 mph, computer says we were getting 31 - 33 mpg today on 93 octane. Gassing up tomorrow and will do the manual computation.

 

I must have an exceptionally fuel efficient ES. My computer typically reads 34 plus on interstate trips. But it is always 1.5 mpg on the high side.

But I'm still very pleased!

 

using 93 octane averaged 33 mpg on a recent trip in the ES 350
it was such a comfortable ride too

 

I have read a number of posts like yours showing very good trip mileage. In fact, I took my 2008 ES350 on a 1200 mile trip and was also seeing very good mileage numbers on the car's computer -- nearly 30 mpg on a trip that included quite a bit of mountain driving. Just for the heck of it, I checked the computer against my figures done the old fashioned way (dividing total trip miles by the number of gallons based on gas pump receipts). Guess what? The Lexus computer is way optimistic! The "actual" (manually computed) mileage was 27 for the trip, while the computer showed nearly 30.

When I took the car in for a scheduled service, I asked the dealer whether or not the computer could be calibrated to show closer to the actual mileage. I was told that there is no adjustment, and that the computer is "just an estimate." Subsequently I sent a question to Lexus asking what the accuracy of the computer should be. That was about 10 days ago, and so far no response.

I think that it is entirely possible that Lexus has made the mileage computer overly-optimistic to give owners a "feel good" impression about fuel economy that may not be entirely justified.

 

If you factor in the built in speedometer error, my ES350 gets just over 30MPG on the highway, the cars display is also about 5% high - - I calculate 30 from the gas pump readout, but they are also not always 100% accurate. My overall MPG over about 14000 miles is 25.4 on the cars display, but even 23+ is pretty good considering my daily commute.

 

Went 237 miles / used 7.1 gallons of premium = over 32 mpg / interstate driving at 73-75 mph.

 

When you put the computer on the "miles to empty" function, it uses the word "approx". I would never hold that computer to the penny, whether it is miles to empty, MPG, or even the outside temperature. It is a great estimate, but it is not 100% accurate.

 

Okay, either I'm confused by the interpretation of your figures or my math skills might be lacking...but how exactly is it possible to have a two-way freeway-only average of >32 when the LV-SF segment was <31 and the return segment was <32?

Pardon my ignorance, but how exactly does speedometer error (i.e., speedometer inaccuracy) have any bearing on fuel economy...not unless you're implying that the fuel economy computer factors in speed data when calculating fuel economy...or that the fuel economy computational accuracy is tied into the accuracy of the speedometer? Yes--how fast (or, how slow) you drive is a factor in fuel economy...but I didn't know that the ES fuel economy computer was capable of computing fuel economy based (in part) on whatever speed reading it was pulling from the speedometer (or more likely, the speed sensor).

 

My calculation was done by hand held calculator, filled up 'till no more would go in.

 

Toneman,

OOPs, that should have been 31.2 MPG. Your math was perfect.

JerryF

 

This is exact my feeling and experience, this on-board computer just make you happy (26 MPG ). But I'm really happy with the real 23 MPG with AC on all the time with mix driving routes.

 

Here is what I typed:

If you factor in the built in speedometer error, my ES350 gets just over 30MPG on the highway, the cars display is also about 5% high - - I calculate 30 from the gas pump readout, but they are also not always 100% accurate.

I did not even imply that the trip computer entered into my calculations, only that it was also somewhat inaccurate.

 

I too see great mileage but as said in an earlier post on this thread the actual mileage is about 5% lower than shown on the Lexus computer. I know this because I tried it with a Garmin and at 60mph on the Garmin the speedometer read ~62MPH. I had just had a similar problem with my SSR due to a gear change and had to reprogram the chip to 410 gears rather that 376. This was a difference of 10% and sure enough the gas mileage on the trip computer ran 10% high and odometer was 10 off - it read more miles than actually traveled. I asked the Lexus service rep about it and he said it is in tolerance. So my conclusion is that your actual mileage estimates will be about 5% lower than the computer says (1.5-2 mpg on a trip). It bothers me that we are recording more miles than we actually traveled. Think of the savings to the Lexus warranty folks.....