cwmoser wrote:
Went to this calculator which calculates Engine RPM based on tire diameter,
Axle Ratio, and Transmission Ratio ...
http://www.crawlpedia.com/rpm_gear_calculator.htm
... and find that with Over Drive OFF at 3,400 RPMs that vehicle speed is
just over 68 mph.
With OD ON, the same RPMs should be 2559 - 840 higher RPMs with OD OFF. 33% more Engine RPMs, so I assume 33% less MPG. I typically
get 14-15 MPG - so I should expect approx 10MPG towing.
I'll have to take my LX470 out and verify that 3,400 is at 68 with OD off.
You're overthinking this. First, you won't want to be towing at 68 mph, especially with a vehicle with such a short wheelbase, even with properly sized and adjusted weight distribution system. If that's your "usual" highway speed forget about when towing, it's just too fast. Secondly, you can't "calculate" in advance what your fuel mileage returns will be when towing a barn door down the highway as there are so many influencing factors such as head wind, side winds, upgrades, passing trucks, slippery road conditions, and all those combined. Most typically cite +/- 10 miles to the US gallon when towing any trailer that sticks up in the air ... under favourable conditions I typically averaged ~ 10.5 mpg towing our previous 5500 lb, 25' Spree, these days I typically average ~ 12 mpg towing our 4500 lb 19' Coachmen. Smaller vehicles like yours, with engines spinning at higher speeds, are likely to be at the lower end of the fuel mileage scale, meaning if you see an average 10 mpg count yourself lucky. You might also want to check your owner's manual as I recall that although my friend's 4.7L Sequoia would run on regular it did far better running premium, particularly when towing ... yours may be the same. As oft has been said, if you're concerned about the cost of fuel then RVing isn't a sport you should get involved in. :W
