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Rx400h - Some Questions From New Owner


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I just bought my RX400h 10 days ago. I like it more every time I drive it, although I wish it had another inch or two of headroom. After all, it's a luxury car, so I'd hope it would accomodate my 6' 7" height better, as my last car did (Mercedes S420). I also wish the fold down arm rest was wider, and that the ML audio was better, but nothing's perfect. I believe strongly in hybrids, and it's an interesting vehicle. It's teaching me to drive all over again, watching my acceleration and slowing down more when approaching a stop. I have a few questions, though.

1. Sometimes it will run on electric up to 32 mph (on cruise control) on a good level road before using engine, whereas at other times it will do as much as 40 on electric power alone. I understand that the engine will often initially run to heat the exhaust system or recharge the batteries, but these findings occurred after driving for awhile and engine had shut off with 70-80% in the batteries. Is there a reason I can't get over 32 mph on electric sometimes? What can I realistically expect?

2. Will the characteristics of the motors vs. engine change as the car breaks in? I've seen where it can take up to 5,000 miles before it breaks in. Will the mi/gal get better during the initial time period?

3. I'd like to put a synth oil in it, but I want to wait until it's broken in. My dealer recommended having an initial 1,000 mile oil change, then the 5,000. Should I change to synthetic at 1,000 miles, or wait longer? I remember reading articles years ago about how, with synthetics, the engine may not wear in enough or hardly at all.

4. I've read the articles referenced here about synth oil, and I think I'm more confused than ever. Would Mobil 1 or AMSoil be reasonable choices? Then again, I don't want to pay $90 for 1 change of oil. I used Castrol synth in my last car for 9 years, a Mercedes S420 (they recommend Castrol synth), and had no unpleasant experiences. However, it looks like it isn't as good as I thought, judging by the test results I've seen.

5. Do the batteries charge any better (faster) when slowing down with pressure on the brake than they do when just coasting? Would it be better to slow down by braking lightly, or to coast further then push harder on the brakes, or does it even matter?

Thank you in advance to anyone who replies with their thoughts.

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Congrats on the 400h. I love mine as much today (almost 14k miles) as I did when I got it -- maybe more.

I'll take a shot at a couple:

1. I don't know about the cruise issue. I can reliably get the electric motor-only operation up to 40 MPH. Sometimes higher, but I won't get acceleration, just a little to help the car keep from going slower. The trick is to keep the kW dial in the white-hashed area. Above 40, below the top end of that area. Again, on cruise, I'm not sure why this varies to anything below 40 MPH. Are ALL conditions the same? A huge difference is the A/C. If the A/C is on then I can't do elecrtic-only above 30 MPH or so most of the time. But this does seem to vary. My comments above are for non-A/C driving (which I do unless really warm outside). Note that the A/C is typically on when the heat is on (when the climate control is on "Auto").

2. I didn't notice any difference after a break-in other than my own driving habits.

3. and 4. I don't know. Others will chime in.

5. Yes. Breaking lightly is better than coasting, then breaking suddenly -- for charging batteries (break harder when needed to avoid something in front of you!). Again, look at the kW dial. "Negative" or "blue" is correlated with charging. The deeper into the blue, the more power is being generated. This was the largest change in my driving habits -- breaking the amount that seemed to optimize power regeneration. The biggest bang for the buck for me is lightly breaking while going down a hill. There is a fairly long hill on my daily commute in which I can get almost three levels of charage by lightly breaking down the hill.

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I just bought my RX400h 10 days ago...

1. ...What can I realistically expect?

You can expect to modify your driving habits a bit for the best mileage. You will get more time on the electrics if you use this technique: Accelerate normally (as brisk as you like) up to cruise speed; then take your foot completely off the Acc pedal for a second and *slowly* reapply the gas until you are just holding your cruise speed. Anticipate the need to slow down and again take your foot completely off the Acc pedal and even lightly apply the brakes as needed to maximize the power needle into the blue range. Note: you can acutally apply the brakes pretty hard before the pads kick in, the motors will do a remarkable job of slowing the car as well as accelertating it ;)

2. Will the characteristics of the motors vs. engine change as the car breaks in? I've seen where it can take up to 5,000 miles before it breaks in. Will the mi/gal get better during the initial time period?

Yes. True. Yes. The Internal Combustion Engine (ICE) compression will rise as the rings seat and this will improve your mpg somewhat. It also inproves the effect on the B position on shifter (more engine braking). Expect that the engine is still breaking in up to 10K (bearing races, cams etc).

3. I'd like to put a synth oil in it, but I want to wait until it's broken in.

You absolutely want to wait before running synthetic. Especially for the rings which should be done by 5K, but you also want the engine to loosen up just a bit all around, so my dealer recommens waiting until the 10K to put in synthetic (Mobile 1, buy 5qts at PepBoys and take it in with your car). As for the 1000k oil change... I have not heard of such a thing... it would seem to me they are trying to get your FREE first oil change out of the way so they can get more service money from you.... wait until 5K, then get your freebe.

4. ...Would Mobil 1 or AMSoil be reasonable choices?

Mobile 1. Get it at your local auto store and save $$. You need 5qts for an oil change.

5. ...Would it be better to slow down by braking lightly, or to coast further then push harder on the brakes, or does it even matter?

Watch the needle go into the blue zone... that will answer your questions. If further application of the brakes does not move the needle into the blue, then you are using the pads rather than charging the batts. Also pay attention to your state of charge. If the batts are near the top, the pads come in sooner.

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First of all congratulations Legacy on trying to take an educated approach to maximizing the hybrid experience in mpg and all around driving enjoyment. I too had to relearn my driving habits with this car and its made me a better driver (i guess i had a ways to go LOL). I agree with what has been posted here, moderation is the key keeping in mind coasting, light braking when you can and anticipating what is going on in front of you. Regarding oil, there are as many answers as their are 400h drivers, i want to point out that your 400h comes from the factory with Castrol synthetic blend and that is what the dealers are using at oil changes. I am one of those oil freaks who believes that an oil and filter change at 1000 miles is a great idea to remove any loose metal fragments on any new car. I have done it with every vehicle i have owned and its been great for longevity of the engine coupled with 3000 mile oil changes. BTW my dealer doesnt mandate the 1,000 first interval, however its also a chance for them to check other fluids and do any early adjustment to your personal settings. As far as the cost of oil change at the dealer, my dealer charges $70 including tire rotation however we see many people here reporting oil and filter only charges of up to $125.

The only way people on this board keep a synthetic oil change under $90 is when they do it themselves, they will tell you it costs more but they do it less frequently. Lastly for warranty purposes isnt it true that synthetic or not Toyota requires you to stick to their reccomended intervals no matter if you have synthetic or dyno oil in the engine. Am i wrong on that last one? I vote for using their synthetic blend and more frequent changes.

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Thanks to all who have contributed answers to my questions.

I've been noticing that on cruise control under 40 mph, after the ice engages to go up an incline, it doesn't seem to want to disengage on level ground. If I "help it along" by accelerating a mile or two above the set speed, then let it coast down, the ice will disengage until the set speed is reached, then the electric will take over. I guess the ice has a little trouble determining if it's needed anymore, maybe to prevent it from starting and stopping too often. I wish it would use the rear motor on electric-only.

Also, I cannot seem to get the "door lock" setting to work. I've done the "start, neutral, lock door for 10 seconds" procedure, yet it still locks the doors upon shifting out of Park, and doesn't respond by locking and unlocking the door.

The car IS fun to drive, though. :D

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