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Drop In Gas Mileage 26 - 13 06 Rx400H

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Up until 2 weeks age, I was getting 24 - 26 mpgs. Car has 87K and has been serviced with oil changes and tire rotation. Changed the air filter and cabin filter recently. checked tire pressure, all @ 30 psi. Can't think of why mpgs dropped so much. Sometimes when car is in the green mode, (green lines on display) it says that I'm only getting 40 - 50 mpg, use to read 99.

Any ideas for me to check? Want to make an apt to have transmission fluid changed this week, drain and fill, no flush, right?

Will check antifreeze later today.



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How cold has it been there? The engine in our Prius v wagon runs more in cold weather. In summer it will run it in EV mode all the way out of the cul-de-sac but in cold weather the engine starts before I'm out of my driveway.

Are you allowing for colder temperatures when you check your tires? Last week I added 5 or 6 more psi to the tires in our cars than shown on the door jam sticker while the cars were parked in our 50 degree garage to allow for outside temperatures down to about zero. Since it could be as low as -10 tomorrow morning I should be adding even more pressure.

Tires gain or lose approximately 1 psi for every 10 degrees of temperature change. If tire pressures are not monitored closely when there are wide temperature swings, tires can become dangerously low on pressure and, of course, diminish fuel economy.

Yes, drain and fill unless your maintenance manual says otherwise.

Winter sucks!

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This winter has been the worst in years, lots of single digits, and 70" in snow, we're expecting another storm today into tomorrow....then temps to drop 0 and below for the next week or so. Time to think about AZ. haha

I'll check tires again tomorrow, if we only get the 3-6" they're calling for, otherwise it will have to wait.

Car engine kicks in as soon as I start the car, and seems to run too often. Getting 13 mpg seems way too low, just thought something was wrong somewhere.

I have Parada X tires on, and I have to say, I'm disappointed in the performance. About 25K miles on them and the last time I had them rotated, the tech said they were worn and I should look for new tires, so maybe that's contributing to the problem?

Thanks for the feedback, Jim

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13 mpg seems bizarrely low for an RXh.. Does your RXh have remote start and, if so, are you using it? Are you running the engine for extended periods to warm the engine and/or interior? I wouldn't think that driving a slower speeds on snow should hurt fuel economy that much since hybrids usually excel at lower speeds.

Is your RXh front wheel drive or all wheel drive. If it is all-wheel-drive, the rear wheel traction motor turning on more often while driving on snow may be a factor contributing to worse fuel economy.

You might try manually calculating your gas mileage over a number of tank fill-ups if you are instead relying on your trip computer. The trip computer may not always be accurate.

AZ is too hot in summer - I don't care if is a "dry heat" - it's too damned hot. Last time I was in the Phoenix metro was in July when it was something like 110 degrees every day. I'll take humid Florida any day as long as I don't fall into a sink hole.

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Forget Florida and Arizona, everyone knows San Diego has the best weather! (Well, not for the last couple of days, but for every other time of the year.)

BTW, our Parada X tires are wearing very slowly. I believe we have 30,000 miles on them and they still have plenty of tread left. They are superior to both the OEM Michelins and the Bridgestones we had, afterward.

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My Parada X are approaching 35k miles...Man I thought I just bought those. You may be doing better on yours, mine are approaching the end...I figure 10k more at most.

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CA is GREAT, I have family in Solana Beach and Cardiff, would love to live there.

I'm thinking that my tires may be the problem for poor gas mileage. I put them on 11/11 @ 63.5k and now I have 87K, and the tires look tired... Hoping Costco will have some next month.

NJ roads are so beat up, I sure that doesn't help either.

The 13 mpg is just irking me.. Next fill up, I'll calculate manually.

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Tips for better MPG in the RX400h:

- Keep your tire pressure at 38-40 PSI.

- Get low rolling resistance tires (LRR) if you don't have them. The OEM Michelin S8 tires are LRR
(Green-X). These will add about 3 MPG to
non-LRR tires.

- Turn off the A/C if possible (summer AND winter, in AUTO mode the AC is
on by default at any set temp). Go to
the climate screen and disable AC, and you can still keep it in AUTO without
running the A/C compressor.

- Use the heat sparingly in winter.
Having a high set temp will make the engine run longer, especially until
the engine is warmed up (157° F and up).
The heated seats can compensate for a lower cabin temp.

- Keep it under 42 mph to allow longer gliding on battery only. Feather the gas to keep it around 40
mph. Works great when the speed limit is
35 or 40. I can sometimes get up to 1-2
miles on battery only.

- A highway speed of 50-60 mph will get you MUCH better MPG than 60-80
mph. My experience in summer: 55 mph -
32 mpg, 75 mph - 26 mpg.

- Don't accelerate hard, coast as much as possible, and brake lightly to
use regenerative braking instead of the friction brakes.

- Buy a ScanGauge computer so you can see the engine RPM and engine temp,
so you can practice keeping it in battery only stealth mode at 0 rpm.

- Make sure to perform the ISC reset any time the 12V battery is
disconnected for service or gets low on charge.
The effectiveness of this is debatable but it can't hurt.

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