Dropped mpg on the RX 400h after a very long drive

[Debra M]

Went on a very long - 4,000 mile - journey for graduation two weeks ago. Drove from Texas to the east coast and back again. In evey non-hybrid car I've had, the mpg rate would always increase with highway driving. No so with the RX 400h (2007). It started out a with a wonderful 27.4 mpg… and kept dropping by tenths as we went along. Now, it has rested at 26.9. I can notice this mpg decrease in my everyday driving. What happened? Can it be improved? I changed the oil and cleaned out the air filter immediately after my return. Does it need a tune up? We've got 95,000 miles on it now. Thanks for your advice.

 

 

[lenore]

Hate to tell you but the 400h gets best mileage in city and when going under 60 mph.  Best I have ever got on highway is 25.6

[Debra M]

I'm smiling about this. Thank you, Lenore. Kinda figured this. I intuitively drive slowly in town, and have noticed good mileage under those terms. By the way, how can you tell if you need new shocks/struts? I'm seeking a smoother ride. Seemed like we felt more NYC potholes than we should have on this trip.

[lenore]

The typical thing is to bounce the corner of the car and see how many times it takes to stop bouncing, over three is too much.  I have 203,000 miles on our vehicle and I changed the shocks because the car felt unstable on a curvy road.  Made a world of difference.  I used KYB shocks and also replaced the upper mounts. 

[Debra M]

You are the best. Thank you for your response and wisdom. Much appreciated.

[lenore]

I just re read your questions, and at 95k miles you are due for a timing belt change.  Many Toyota and independents can perform this for way less than the Lexus dealerships.  Other than that until you reach 125k miles your maintenance other than coolant change, oil changes, etc.  At 125 k the spark plugs are due.

[Debra M]

Timing belt change. Got it. Thank you, Lenore.

[sorcerer]

Hybrids are great for stop-start town driving and speeds of up to (say) 30-35mph where the traction battery does most of the work. At highway speeds and on long runs, they just become 'ordinary' gas-driven cars that will use a bit more gas than they probably otherwise would do, due to the fact that they are dragging around the extra weight of a big, heavy battery.

[Debra M]

Not to mention some big, heavy bags and some (ahem) big, heavy passengers. Thank you for your explanation.

[RX400h]

While this is also true of the Toyota Prius, its 53 MPG highway is quite a bit better than almost all non-hybrid vehicles. Of course, its aerodynamic profile is much better than that of a big SUV.

[TerryMac]

On June 1, 2017 at 11:51 AM, lenore said:

I just re read your questions, and at 95k miles you are due for a timing belt change.  Many Toyota and independents can perform this for way less than the Lexus dealerships.  Other than that until you reach 125k miles your maintenance other than coolant change, oil changes, etc.  At 125 k the spark plugs are due.

Lenore, I just had my 90K maintenance on my 2008 RX400h including timing belt and water pump. I have had the car for a year now but my highway mileage is actually better than in town driving. I get maybe 23 highway and 20 in town. Love my car but would love to get the 25 to 27 mpg overall mentioned above. Any hints? Thank you.

[lenore]

I would try an ISC reset, do a search for the procedure on this site.  Remember our winter gas is not ideal in CA and also the engine comes on more during the colder season.

[RX400h]

Well, it is currently 70 degrees F, here in San Diego. Our gas mileage is A-Okay during this time of season.

[lenore]

Unfortunately all gas in California has winter blend.

[RX400h]

Ambient temperature differences can change fuel mileage. When we hung around Mt Laguna, our mileage dipped. There could be a 30-40 degree temperature drop at that elevation compared to sea level, so the change in mileage doesn't surprise me.

[Les Lex 2018]

After 4.5 years driving the Camry 2.5 H and trading up to the V6 RX-350, I can tell you the following:

Best Camry H MPG was in the suburbs always hit rated at 43.

Second best is 50 MPH on state divided highway, 45 MPG where you can run under 60 MPH.

Worst was city under 7 miles distantly from point A to B - 38 MPG

Next worst is Interstate running at 70 to keep from getting run over.

Contrast: My RX-350 non-H gets only 21 mixed town/suburbs and 26 on the interstate. Based on size, weight and engine size differences, no complaints or surprise there.

The H is perfect for someone with long commute times in heavy traffic.

Freeway fliers? Not so much better than a non-H.