Thanks, however the conflicting responses in this thread make it harder for me to come to a decision. You did not mention if you parked outside at nights, like I have to do. Anyways, I will be getting quotes for installing a block heater both from local Lexus and Toyota dealers. Experience has shown me that Toyota dealers do the job as well with much lesser labor charges.
I'm still good until the end of this month, since my vehicle was parked outside my garage in Toronto right through last winter with temps falling below -20 C and no problem.

 

I agree with budworm. I am on my second diesel car and they have never ever had a problem, my first diesel didn't even come with a block heater either. I too am in the GTA with a car outdoors. My wife's 2010 450h has never ever had a problem in the winter.

 

 

While I do agree that the OP probably does not need a block heater, one would make life much easier. If for nothing else, and even though the factory heater indirectly heats the coolant, getting into the thing and having the heat work right away is always nice.

FWIW, here are two personal weather stations sharing data on Weather Underground, one in Saskatoon, SK, and the other in Greensboro, VT. Take a look at the current temp as well as the historic ones recorded in Jan and Feb.

https://www.wunderground.com/persona...20181107/myear

https://www.wunderground.com/persona...20181107/myear

 

Block heaters "directly" heat the cooling system (as opposed to the oil)

 

The OEM block heater for the OP's RX is a cartridge that gets inserted into the metal block and does not come into contact with the coolant or oil.

It heats the block itself, which in turn will warm/heat the coolant and oil in the block. Doing it this way makes the thing easier to install and you don't have the risk of creating a coolant leak like you would with the old type frost plug heaters that heated the coolant.

 

Thanks so much for this piece of information. I've never dealt with this kind of block heaters before. Although it sounds much "cleaner" to install without creating puddles, I'm just scratching my head since trying to warm the block instead of directly warming up the coolant/oil makes the heat dissipation much greater. Well, I'm sure Lexus engineers know what they are doing ..
Thanks again..

 

I will cruelly add to your confusion. Being north-east of the Toronto core, and last winter having been very, very cold we saw quite a few nights where the temps at night went below -30C (one night went as low as -35C, and that's NOT wind chill values). While my RX is parked in garage, we have an old 2004 Sienna that parks outside with near 250,000km on it. It turned over a bit slow in the early morning on these brutally cold days but fired up every time. Even when the original OEM battery was 10 yrs old and barely could turn the engine over in the winter, it still started (finally replaced the battery at 11 yrs and the current has 4 yrs on it) So to block heaters I say bah, humbug!

Block heaters were definitely needed back in the days of the carburetor, I've had the joy on super cold mornings in my early driving days of standing over carbs spraying quik start, booster cables out, tripping over block heater cords, etc. Those were NOT the good ole days. These days fuel injection systems are highly competent at starting in really cold temps. As long as your engine and sensors are in good condition, just make sure your battery is good too. The battery is really going to be your go/no-go component.

 

There seems to be a confusion between human comfort/convenience and machine requirements.

With petrol/gas engines you need to make sure the coolant has not expanded [in the confines of a pressurized environment) to burst something and oil is able to flow and the battery can produce enough juice for starter to turn the engine.

When it gets to diesel engines, the ignition would not happen till the compressed air (during compression stroke), reaches high temperature. With cold chamber, it takes a whole lot longer [due to high compression --> excessive current draw from battery -> usually the battery dies before the temp can be raised to fire the diesel engine]. There thy have to install heater plugs etc and even put a blanket on the battery, and in many places, just let the diesel engine run,

Back to gas based personal use vehicles ... you make sure there is the right antifreeze and the right viscosity of oil and then every thing is for human comfort.

Salim