Car here is a 2002 Honda Accord V6 with a 4 speed auto transmission.
I have done some extensive testing and found that an external transmission cooler in serial with the OEM radiator cooler will lower my fuel efficiency.
I am located in Texas, so it never get very cold here, but it will still lower my MPG with 1.5 to 2 MPG.
After adding a Perma-Cool model 1060 oil-thermostat to bypass the external cooler, my fuel efficiency got back to normal.
The OEM cooler is always in the loop, and the external cooler is bypassed until the ATF temp exceeds 180F. The thermostat will only open and send fluid through the external cooler under heavy load in the summer. This time of the year, the fluid temp never got high enough to open the thermostat.
In my case, the thermostat is saving enough fuel to pay for itself in about 10000 miles.
Good info for anyone that has external cooler in a cold climate and would like to save some fuel.
I have done some extensive testing and found that an external transmission cooler in serial with the OEM radiator cooler will lower my fuel efficiency.
I am located in Texas, so it never get very cold here, but it will still lower my MPG with 1.5 to 2 MPG.
After adding a Perma-Cool model 1060 oil-thermostat to bypass the external cooler, my fuel efficiency got back to normal.
The OEM cooler is always in the loop, and the external cooler is bypassed until the ATF temp exceeds 180F. The thermostat will only open and send fluid through the external cooler under heavy load in the summer. This time of the year, the fluid temp never got high enough to open the thermostat.
In my case, the thermostat is saving enough fuel to pay for itself in about 10000 miles.
Good info for anyone that has external cooler in a cold climate and would like to save some fuel.