Greetings,
I have a 2008 Sienna with a towing capacity of 3,500 lbs. I am towing a camping trailer that weighs 3,500 lbs and has the aerodynamics of a parachute
Believe it or not, i get 35 mpg highway without the trailer and 15 mpg with the trailer....
I have installed one of the largest capacity ATF coolers I could find (21,000 BTU rating) and a Scangauge II to monitor the ATF temperature.
On a hot summer day (100 degrees Farenheit) after towing for several hours, the ATF is in the 200-210 degrees Farenheit range (and peaked at 222 degrees Farenheit). This is hotter than I would like.
I drain and fill (4 quarts) of ATF every 7,500 miles. In the next few weeks, I am going to drop and clean the pan, flush out all the ATF via the cooler lines and install a Magnefine filter.
My Sienna requires Toyota WS. I am considering switching out the Toyota WS for Amsoil Fuel-Efficient Synthetic ATF. My sole motivation is superior protection - I am not looking to save money. My layman's knowledge on this topic is that synthetic oils offer better protection - especially in a hot environment.
Any comments or suggests appreciated.
Thank you,
Gunter
I have a 2008 Sienna with a towing capacity of 3,500 lbs. I am towing a camping trailer that weighs 3,500 lbs and has the aerodynamics of a parachute

I have installed one of the largest capacity ATF coolers I could find (21,000 BTU rating) and a Scangauge II to monitor the ATF temperature.
On a hot summer day (100 degrees Farenheit) after towing for several hours, the ATF is in the 200-210 degrees Farenheit range (and peaked at 222 degrees Farenheit). This is hotter than I would like.
I drain and fill (4 quarts) of ATF every 7,500 miles. In the next few weeks, I am going to drop and clean the pan, flush out all the ATF via the cooler lines and install a Magnefine filter.
My Sienna requires Toyota WS. I am considering switching out the Toyota WS for Amsoil Fuel-Efficient Synthetic ATF. My sole motivation is superior protection - I am not looking to save money. My layman's knowledge on this topic is that synthetic oils offer better protection - especially in a hot environment.
Any comments or suggests appreciated.
Thank you,
Gunter