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Lexus RX 400h - MPG-Real World Numbers

311 messages,  Last post on Jul 08, 2009 at 3:52 PM

You are in the Lexus RX 400h Forum. Your Host is pf_flyer

What is this discussion about? Lexus RX 400h, Fuel Efficiency (MPG), SUV


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#273 of 311
Re: Question of Style [grallaj] by avery1
Aug 18, 2007 (6:42 pm)
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Replying to: grallaj (Aug 18, 2007 9:14 am)

Congratulations. Do you mind telling what you paid?
#274 of 311
Long term hybrid owners by pf_flyer HOST
Aug 21, 2007 (4:02 am)
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If you are a long-term hybrid owner, our Senior Editor, John O'Dell, would love to hear from you! A short email with your maintenance experiences and concerns would be great. Please send to John at jodelledmunds.com by close of business Wednesday, August 22, 2007. Be sure and include your Forums username.
#275 of 311
Re: Question of Style [richcbt] by chadx
Sep 24, 2007 (11:24 am)
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Replying to: richcbt (Aug 18, 2007 12:07 am)

>>> I drove my RX400h for a while on regular and it runs fine, but to me it runs a little better on the 91 octane. >>>
 
On these vehicles, as with non-hybrids rated for 87 octane, there is no mileage or performance benefits to running high octane gas. You simply pay $.20 extra with no benefit. The engine is designed with a low enough compression ratio for low octane. High octane gas resists self-detination at higher pressures, but unless your engine is designed to take advantage of this, there can be no benefit.
 
Note that on modern vehicles where premium (high octane) is recommended, you can run low octane without damage to the engine. The vehicle will compensate for the low octane by tweaking the timing, ignition, etc. (Note: older vehicles do not account for this and detination, and engine damage, can occur). When running low octane in modern premium-recommended vehicles, an associated decrease in performance and mileage will occur. But for an engine desinged for low octane, no performance or mileage increase can be realized by running premium.
 
On a related note, for an accurate 'operating cost' and mileage comparison, a person should consider the manufactures recommended octane when choosing a vehicle. For example, if a vehicle, where premium is recommended, gets 20mpg and another vehicle gets 20mpg with regular octane, and there is a $.20/gal price difference, over 20,000 miles, 1,000 gallons of gas is used. For that 1,000 gallons, a $.20/gal difference amounts to $200 extra for fuel costs from two vehicles that get the exact same mileage. (Your savings may vary if your area does not have a $.20/gal priced difference between Premium and regular).
 
So, not only does the RX hybrid get much better mileage, but it does so on $.20/gal cheaper regular gas rather than using premium gas like the RX330 non-hybrid.
 
#276 of 311
Re: Question of Style [chadx] by lansdownemike
Sep 24, 2007 (11:55 am)
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Replying to: chadx (Sep 24, 2007 11:24 am)

Unless I've misread your note, it seems that there's a contradiction, and I look forward to understanding it better. You seem to agree that where premium is recommended, a decrease in mileage will occur when you use regular gas. Then you say that "On these vehicles [the RX hybrid] there is no mileage benefit." Is it your understanding that the manufacturer does not recommend premium? My owner's manual as well as the website require premium fuel. The website (footnote 3) says: "Ratings achieved using the required premium unleaded gasoline with an octane rating of 91 or higher. If premium fuel is not used, performance will decrease."
 
Can you help with my confusion here?
#277 of 311
MPG per computer vs old fashioned calculation by gog8rsz
Oct 04, 2007 (12:29 pm)
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I've had the '07 RX 400h for 4 months and have 6200 on the odometer. The computer shows that I'm getting 25.6 in town and 26 on the road. This is in flat Florida. In the montains of NC the computer says I was averaging 29. I'm a conservative driver and strive for maximum MPG. To check the accuracy of the computer around town, I did a manual check on the MPG, dividing the miles travelled by the number of gallons to fill-up. My calculation revealed actual MPG of 22.3 against the computer average of 25.6. Has anyone else done a similar validation? I really enjoy the car, but would be very disappointed if the computer actually overstates the MPG.
#278 of 311
Lexus RX 400h hybrid computer for MPG by kyxydj
Oct 04, 2007 (1:18 pm)
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I've found that the MPG computer in my 2006 RX 400h is fairly accurate, although I have a friend who says the one in his Prius is "optimistic." I find that a "manual check" of my miles per gallon can be an inexact science, depending on which pump, at which gas, station I am using. They all seem to shut off at different times when they think my gas tank is full. But when I've worked out the MPG "manually" I've found numbers higher and lower than what the Lexus computer says, so I'd say it's pretty good. BTW, I stopped resetting my MPG computer at each fill up; I now have driven almost 3000 miles since my last reset, and the average MPG is holding at 29.0.
#279 of 311
Re: Lexus RX 400h hybrid computer for MPG [kyxydj] by kaperino
Oct 04, 2007 (3:40 pm)
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Replying to: kyxydj (Oct 04, 2007 1:18 pm)

Curious on the manual calculation. Do you include the two extra spare gallons in reserve when you caluclate?
#280 of 311
Re: Lexus RX 400h hybrid computer for MPG [kaperino] by gog8rsz
Oct 26, 2007 (12:50 pm)
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Replying to: kaperino (Oct 04, 2007 3:40 pm)

In doing the calculation, I determined the number of gallons to fill-up. When the automatic pump cuts off, I can usually get in about 2 more gallons. It is a max fill,just before overflow.
#281 of 311
Re: Lexus RX 400h hybrid computer for MPG [gog8rsz] by sdk43
Nov 08, 2007 (12:38 pm)
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Replying to: gog8rsz (Oct 26, 2007 12:50 pm)

Our 400h is almost two and half years old.
In the NY-CT area on 87 octane we average 26-27 mpg, and 28 mpg if we take hour-plus trips and stay below 70 mph. I tried one tank of 91 octane last spring and mileage seemed to be 1-2 mpg higher, but that doesn't do more than pay for the higher price so we use 87 octane.
Speed makes a big difference--even if our mileage indicator has not been reset for over 200 miles, if we get up to 75 mph you can see the integrated mileage number drop in a matter of minutes.
#282 of 311
altitude, mileage, tuning the computer by scarfoot
Nov 19, 2007 (8:34 pm)
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Had the rx400h for 6 months and very pleased. I can get 30 mpg on the computer driving carefully with a mix of highway and city driving in warm weather here at 6000 feet elevation using premium fuel. My wife likes higher g forces and gets closer to 27. Anyone else have experience at altitude? An earlier post on this forum describes it as effective to accelerate quickly to speed and then take the foot off the accelerator quickly to engage the electric motor and that this strategy enhances fuel efficiency. Physics seems counterintuitive, but maybe that's the way the car's computer is programmed. I should think that it would be easy enough to "tune" the software for better performance or better fuel economy. I'm a little surprised that this is not possible for the driver to do as a matter of individual preference. Maybe next year.

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