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Whoops!!!!!! Just realised that your car isn't a hybrid so forget what I wrote. It might be the 12 v. battery, though. Typically they last up to 10 years nowadays but I expect that there are a few early failures. Check its voltage ... if flooded cell lead acid should read at least 12.5 volts, rising to 14 or more when the engine is running. If 12.0 then it's suspect.

When you say that it hesitates and struggles, is that the sound of the ICE or is it the "ready" light hesitating before lighting up? The former suggests a traction battery fault as that supplies the electrical power to turn over the engine. Traction batteries have a very good record for reliability. The latter suggests a fault with the 12 volt auxiliary battery which has to power up the electronics which control everything. I've had the latter and have installed a small digital voltmeter in the central storage compartment which I check at every cold start. The auxiliary battery seems to lose voltage rather too quickly for comfort ...the system powers up at 11.5 volts ok but that seems very low for a 12 volt battery. I believe that I read that 10.8 volts is the minimum that will power up the electronics.

I emailed HJ a while ago saying that I was firmly opposed to left foot braking (having tried it once and owning both auto and manual cars). He maintains that it's safer as your left foot has less distance to move to get onto the brake pedal. I think that that's outweighed by the advantage of your right foot having its position calibrated by the accelerator so that in an emergency you can be sure of moving it accurately onto the brake. There is the other aspect that if you drive both manual and automatics then your left foot is trained to use the clutch pedal which is a quite different action from the brake pedal.

I don't understand how you can deliberately run down the traction battery. My understanding is that it's charging is controlled automatically in order to ensure that there's always sufficient charge to keep the 12 v auxiliary battery charged, to be able to start the ICE and to cycle the batteries state of charge so as to promote its longevity. Have I missed something?

I've only used the nearest Lexus dealer for this car which is where I bought it so they changed the battery which says "Toyota" on the side so I assume that it's the correct one.

I own the car as a convenient implement to use when I need to, not when I have to to keep it in running condition. I've owned cars built in 1932, 1949, 1956, 1958, 1958, 1964, 1973, 1978, 1985, 1986, 1990, 1996, 1998, 2005 and 2015 and the last one is the only one which has been this needy. Battery lives have improved over the years and I now find average 10 years or so except for the Lexus. Just to clarify, I own 3 cars... a 1958 MGA which I restored and put on the road in1983, a 2005 Honda Jazz which I bought new and the 2015 Lexus. We're both retired so no commuting mileage, the MG is just for pleasure in the summer months (and retains its battery charge for months), the Jazz is for rough use such as transporting mucky stuff, towing a trailer etc and the Lexus is mainly for longer trips. Sounds pretty extravagant but we're not hard up. I'm very pleased with all aspects of the Lexus except for this auxiliary battery business. which I feel could easily be fixed.

My late -65 IS300h went in for its 4 year service last week and came back with a note on the Hybrid Health Check that the auxiliary battery shows signs of deterioration and that I should contact my Service Advisor. I did this but the only advice that I received was to use the car more. Apparently during the HHC the auxiliary battery voltage dropped to a level where warning beeps were emitted. This is with a replacement battery supplied last November. I have taken to monitoring that battery voltage at the time of switching on just to see how long the car can be left and the voltage so far is never less than 11.5 which is sufficient although remarkably low for a 12 v AGM battery. Anyway I received an email from Lexus HQ asking my opinion regarding the service and so I took the opportunity to spell out the history a bit with the underlying question that I've never before owned a car that required such regular use in order to keep it in a startable condition ( think 2 week holiday with car left in airport car park). My suggestion to Lexus is that the battery is under specified for its task. I await developments.

Never switching the system off could well be the solution. I never switch off and I've never had any problem with smelly aircon systems in 27 years of having cars with such systems and the first car was 12 years old and the second was 20 years old when sold whilst a current Honda is 14 years old. My IS 300 h will be 4 in December.

The only time that I have felt strong regen is when dropping down a gear or two using the paddle for example when descending a hill. Could your effect be due to the traction battery running low and requiring charging?

Sway bars (used to be called "anti-roll bars") go some way towards reducing the independence of independent suspension and so any beefing up of them comes with disadvantages. OK for track use maybe.

Stand by for some physics. Boyle' Law states that for a fixed volume of gas ie. in a rigid container, pressure is proportional to absolute temperature ie degrees Kelvin. 30 Celsius is 303 Kelvin and 20 Celcius is 293 Kelvin. A reduction of temperature from 30 C to 20 C will reduce pressure by a factor of 0.967 or from 36 to 34.8 psi. .An initial temperature of 40 C would give a reduction of 0.936 or from 36 to 33.7 psi. In practice the tyre will shrink in volume slightly as the pressure reduces but that won't be a big effect. It would seem that cooler weather can explain only some of the pressure reduction. If you inflate your tyres at a filling station then they will be slightly warm as a result of having driven there so need to be at least 1 psi higher to compensate.

The solution is to inflate them back to 36 psi which is the recommended pressure. I wouldn't be happy to run them at 30 psi. if the handbook says 36.

Interesting that, about the brake booster pump. I'll listen for it next time I get in the car.

It does seem to me that there's a problem with the IS300h 12v battery. I had a replacement under warranty for a 3 year old battery and yet my experience with other/ previous cars is that the battery lasts around 10 years nowadays. My Jag. Xj8 battery was 15 years old when I traded in the car and had never, ever, needed any attention and that was with an annual mileage of only 3,000 so it didn't get much charging. My Lexus quiescent discharge has been measured by the dealer at 16 mA .... well below the max. permitted figure of 30 mA and the battery shows 14.0 to 14.3 volts when the car is switched on so there's nothing wrong with the charging system but the battery voltage falls to 11.5 to 11.7 after being left unused for 3 days. This is sufficient to start the hybrid system but seems peculiarly low for a 12 volt AGM battery.

I can imagine it happening if the bonnet was inadvertently closed with some tool ( screwdriver?) left lying on top of something in the engine bay ...presumably on the offending side. Any signs of an indentation of any surface on that side?