I find two references for recommended oil in the 2009 manual.
Section 4.3 Do-it-yourself maintenance, p357 recommends 5W-30 and says, "If SAE 5W-30 oil is not available, SAE 10W-30 oil may be used. However, it should be replaced with SAE 5W-30 at the next oil change."
Section 6.1 Specifications, p 471, it says, "An oil with a higher viscosity may be better suited if the vehicle is operated at high speeds, or under extreme load conditions."
The first number in an oil designation (the W number) refers to cold weather viscosity. A low number means low viscosity so the engine will start easier and oil will be able to flow where it is needed when the weather is cold. The second refers to operating temperature viscosity. I guess that they are recommending 5W-30 over 10W-30 for winter starting. The language in both sections implies that low viscosity oil will improve fuel economy, and that seems to drive their recommendation for 30.
As far as I can tell, commonly available oils are:
- 0W-20 (never heard of it, but 4-cyl RAV4s are supposed to use it)
I would say that for towing a 17-foot egg over the passes we have around here, 5W-40 might be the optimum choice. It might be a little harder to find, but Quaker State 5W-40 does show on Canadian Tire's website. I figure that I'll change the oil twice a year, using 5W-30 in winter and 5W-40 in summer.
I wonder about synthetic oil.
About hitches, Section 2.5, Driving information, p. 213 makes the recommendation about removing the hitch and sealing the holes, but I don't see any mention of weight distributing hitches.
Removing the hitch when not in use will definitely save fuel. One could argue that it would improve the look of the vehicle. Not that the back end of a RAV4 is very pretty to start with. At least this year all models get that nice spare-tire cover.