This is probably obvious to the rest of you, but as a 3-month owner of a beautiful 2010 RX450h it only became obvious as time went by.

Just finished a great 4-day holiday from Portland Oregon to the coast (a quiet little town named Alsea). Fuel economy on the 4-hour trip was a surprising 30mpg, twisty mountains and all, and with highway speeds around 60. Coming back a different way with freeway speeds of perhaps 70mph dropped the economy to around 26mpg.

By contrast, here in suburbs I do mostly 5-10 minute trips, and fuel economy is terrible, around 19mpg. So what clobbers economy is the engine warmup, especially now that for every trip the engine temp starts at maybe 30 degrees F. Takes a lot of fuel to bring up the engine to normal operating temps, but once there the car is magical with fuel economy.

It would be even worse without the exhaust heat exchanger. Great idea to tap that otherwise-wasted heat source, but I wonder how much maintenance that device will require?

EDIT 24 Jan '17: Make that more like ~16mpg on the short trips.

 

I too notice that driving at low highway speed greatly enhances the fuel economy - it's just I can't and don't wan to drive at low highway speed. My cruise is set at 74 mph (9 mph above CA highway limit) and add/subtract speed depending on traffic. at that speed, I see about 24.5 mpg. Surprisingly, I get the same stats driving the mean streets of Los Angeles with a bunch of unlicensed, uninsured and untrained motorists yapping away on their cell phones.......

On the other hand, I had a chance to drive a similar model in Japan. I got something like 7.6 liters per 100 km. (that's like 31 or 32 mpg) The whole population over there don't accelerate quickly and stops so gently. They rarely cut you off - so not much jabbing on the brakes.

makes me wonder what kind of mileage I'd get driving that style in a regular ICE car.

 

This makes me even more grateful for the fact that I can keep my '10 RXh in my garage where the temps almost never get down below about 50°F, and generally hover in the 55-60°F range.

 

While everybody makes a big deal worrying about the possible cost of replacement of other hybrid components like battery and inverter, this is actually the component I fear the most likely for failure. It is a very expensive component - probably thousands to replace, directly exposed to the elements and road hazards, subject to huge temperature variations. As this was not a feature on the 400h, I am wondering as the 450h begin their second decade of service how many of these will end up with bypassed systems when exhaust systems eventually start to leak.

 

Droid, could be right, but I noticed a month ago that eBay now has used but serviceable exhaust exchanger assemblies (from totaled 450h's, I assume) for maybe $1K. So maybe expensive but not too expensive to keep them running.

 

IIRC, that exhaust system comes in at $3,600 U.S.!

 

Here's an older account that makes me never want to take mine on a rough road:

http://us.lexusownersclub.com/forums...achilles-heel/

But I assume eventually the elements will get at it. The main housing will probably last quick a long time, it's the little tubes that are most vulnerable and probably harder to repair rather than replace.