Brabusx2

as title stated, Vegas is getting really hot, and really dry as usual, so dry heat, it burn your throat as you breathe, so kinda imagine what it does to car as well, yes blasting AC...

had my car for over 6 years, but this year it seems like the heat does huge performance drop on the car, dead stop to 20mph is fine, but 20mph to 50mph the engine sound like revving really loud but not moving much at all, i kinda felt like the car tranny is slipping

car is a GS450h with 120k miles btw, winter time without AC i can average 26mpg, summer time 19-21mpg

going to drive to LA on July 1st, going to see if cooler weather does make differences or my car has issue.

had waterpump replace under warranty back in 2015 90k miles, hybrid battery replaced 11/2015 as well
never encounter summer heat and performance issue, or is there something wrong with the car? no code showing up

Sodium

Yep. At 68F the air has a density of 1.21g/L, and at 125F the density is 1.09g/L. That means there's about 10% less oxygen available to the engine at 125F, so it has to work harder for the same amount of power. Also, having your AC blasting will put more load on the engine. Heat is also the biggest killer of rechargeable batteries – might be that the batteries go into a reduced output mode when the ambient temperature is high so that they don't get damaged? The reduction in gas milage is substantial, but as long as you don't notice anything else and it improves when Vegas cools off I wouldn't worry about it!

Maybe the spark plugs and/or air filter are due for replacement?

As for 20 to 50 feeling slow, has the fluid in your transmission been changed?

Brabusx2

thanks for the reply,

tranny fluid were change at 90k miles at a indy shop, tbh, i couldn't feel the differences at all since the car were CVT, but the shop owner told me it was really dark, no fluid are lifetime, anway,

plugs were change at 110k miles, air filter might need cleaning soon they are K&N drop in and its been awhile since i wash it.

at night driving the car feel so much smoother the power came back, but will see next weekend when i head to socal and see how the 70s weather affect the car

Vooduguru

I just hit 180k miles on my GS430, and my thermostat took a crap on a day that got to 100+. Fortunately I was able to limp it the 2 miles home when the thermostat wouldn't open. a LOT of the coolant was gone, changed the thermostat, refilled the reservoir enough times to add 1.75 gallons of coolant. It got to the max temp on the gauge for like MAYBE 3 minutes before I turned the car off, let it cool down, and drove it (coasted) it down the hill the 2 miles to my house. Let it cool down, and put in a new thermostat. Never overheated since. Oil looks decent too, but I'm gonna change it here in a couple days just to be on the safe side. I would recommend draining ALL the coolant, and refilling it with that PINK Asian/Toyta/Lexus coolant so you have "new" liquid in there. Wonder if I can put a bucket of ice in the bottom of the airbox to cool the air charge? lol

Brabusx2

i always hear thermostat in car, but knock on wood i never have car with thermostat issue, where are they located? how do they go bad? easy to replace?

i always hear my friend audi/VW always have that issue.