Hi Everyone

I'm considering buying a 2010 Lexus RX-350 with 150K miles this Saturday. I have test driven and did not notice any mechanical issues. I did ask the owner if he had changed the oil cooler lines, which he said he has not. I'm not sure if the prior owners have changed it. But I will be buying the car accepting that I need to change the oil cooler lines.

I have been doing some research on the car and I have read some reports that the transmission is weak. I don't plan on towing anything heavy with the car, but I do plan on carrying kayaks on the roof rack.

How well do the transmissions hold up generally? Can I expect the car to last to 300K with regular maintenance?

Should I change the trans fluid after I buy the car?

 

Welcome to CL. These transmissions like any do benefit from having the fluid changed. They are very reliable overall.
You can check the dealer maintenance history at the Lexus Drivers Site which I provided a link for below. Join for free and enter the VIN. Then look up the service records.

By 150,000 miles it should have had the spark plugs replaced, the coolant replaced and hopefully someone changed the transmission fluid and if AWD the transfer case and differential fluids. If you get it you should change the ATF. A few drain and fills will be safer than doing a fluid exchange also known as a flush as it is easier on the transmission. I would also change the brake fluid and lube the caliper slide pins.

You only have the oil cooler lines if you have the towing package. That does not mean you have a hitch. It means you have an extra oil cooler and wiring. You can look under the car and see the lines. Search Google or here for photos.
​​​​​​https://drivers.lexus.com/lexusdrivers/account/register

 

Quite a few of us have changed our own ATF, usually by performing three separate cold drain-and-fills because only 2 to 2.5 quarts of ATF can be drained each time. I did so in late July 2021 on my wife's 2015 RX350 FWD at about 65,000 miles. I stuck with Toyota WS ATF as recommended in the specs, ordered on amazon.com (get 7 to 8 quarts to make sure you have enough for the job) where you can usually find various Toyota WS ATF deals. I did my initial ATF drain-and-fill first thing one morning which replaced 2.25 quarts (always measure what drains out and add that same amount of fresh ATF back in, assuming you have no leaks). She drove the vehicle 40 miles or so afterwards, then I let the vehicle sit overnight and did the second ATF drain-and-fill first thing the next morning, again replacing 2.25 quarts. She drove the vehicle another 40 miles or so afterwards, then I let the vehicle sit overnight again and did one final ATF drain-and-fill first thing the next morning, again replacing 2.25 quarts. My guess is that the transmission now contains 85% to 90% of fresh ATF and that should be good enough. I expect to repeat this process at 110,000 to 120,000 miles, assuming we still have the vehicle then (it is now approaching 82,000 miles). Works for me....

 

Just added the car to Lexus account and did not see tow package. Also called the dealer and asked them by running my VIN. Looks like the car does not have the tow package. That will save me the time not having to change the pipes.