Can I tow without Tow Package?

Definitely a good idea to add the trani cooler. They're not expensive and really do help the engine run cooler. I would think a Highlander would be very capable of towing an MPG, even without a tow package. You can usually get the tow rating by putting your VIN into a decoder, or checking Edmunds, Blue Book, etc. You might also want to consider an oil cooler for additional protection.

Depending on manufacture, the tow package can contain many different things if not all of them. Tranny cooler, engine oil cooler, different radiator, different radiator fan, different programing for the engine and transmission, brakes, suspension, tires, gear ratio, hitch, wiring, etc.. just to name a few.

When towing I have always been a big fan to monitoring vehicle parameters - tranny temp, oil temp, coolant temp, exhaust gas temp (mostly diesels and turbo gas engines), etc.

Edge Products (there are others) makes a generic OBDII digital monitor (plugs into your on board diagnostic port) that measures onboard sensors that come from factory - you can do your own research, or call companies like Edge and ask them what their product will measure and show for your specific vehicle. Well worth the price of monitoring the health of your vehicles key parameters.

Here is a link to the Edge product for reference --> Link

I would think there would be other forums specfic for the Highlander where others with the same vehicle have towed, upgraded for towing, etc. Good luck.

Brian

I'll second the suggestion as to monitoring vehicle data while in route. My GMC 3500 diesel has the LLY engine which is famous for overheating. I installed a similar monitoring system (Bank IQ) to the Edge and have found it very useful as to what is happening under the hood at any given moment. I am towing hard and near the limit and I'm never near the overheating stage other with a LLY talk about.

The best thing to do is get a larger tow vehicle but until then coolers and gauges.