Originally Posted by DryFly
I do think you're pushing it as far as using your Lexus for a tow vehicle if you are at the maximum gross weight and tongue weight. First, the tongue weight is probably "dry", meaning it doesn't take into account water, gray water tank and black water tank, and probably no propane. Also, I bet the trailer, once you load it up with all your stuff and water and propane will probably weigh more than the 3500 lbs.
Actually, the OP indicated that the gross trailer weight was 3500 pounds. That's not a dry weight, that's a loaded weight. Though of course it IS possible to overload the trailer; all your stuff adds up quickly.
You need to look at THREE criteria for your tow vehicle:
1 - Receiver rated capacity, which you indicate is 3500/350;
2 - GCWR, or Gross Combined Weight Rating, the maximum weight of tow vehicle and trailer combined;
3 - Actual loaded weight of your tow vehicle, including the trailer tongue weight. If you don't know this and don't have access to scales, use the GVWR.
To give you an example, my Airstream Interstate class B motorhome has a receiver rated for 7500 pounds and 750 pounds tongue weight.
GCWR is 15,300 pounds.
GVWR is 11,030 pounds.
So, how much can I tow based on those numbers? The answer is NOT
7500 pounds. If I have my Interstate loaded to maximum capacity, the most trailer I can tow is (15,300-11,030=) 4,270 pounds. To find the actual towing capacity at any given time, I'd have to weigh my Interstate, fully loaded, add in the actual trailer tongue weight, and subtract that number from 15,300 pounds.
If you want to really
be safe, you'd also have to look at gross axle weights, front and rear, for the tow vehicle, and make sure you don't exceed either
axle's rated capacity when everything is hooked up and fully loaded.
I tried looking up the GVWR and the GCWR of the Lexus 400h, without any luck. Even the Lexus website only lists curb weight and towing capacity. So you'll have to consult your owner's manual, or the data plate on the driver's side door post to find the GVWR, GCWR and gross axle weight ratings.