I had posted before about using a Mazda 5 as a TV for a Boler
13 ft. Concern was expressed as this vehicle is not rated for towing in NA but is in Europe / UK.
This is my setup and experience, having just come back from a 10,000km road trip that included crossing mountain passes in the Rockies, both in BC and in WA.
The GVWR on our vehicle is 4600 lbs, split approx 50/50 between the front and rear axles. Taking into account the weight
of the vehicle, we could add a max of 1200 lbs if I recall correctly. That was 4 adults, a dog, a full tank of gas, and 150lbs of tongue weight
on the trailer. We were close to being maxed out by my calculations but not over the limit.
So off we went to the truck scales to check things out. We used the city-owned scales by the Alex Fraser bridge and it didn't cost us anything. We were just right, and the Boler
, mostly-laden, came in at around 1500 lbs. So I was pleased - we were under the 2000 lb limit of the tow hitch, and tongue weight
was 10% of trailer weight.
I installed a Tekonsha P3 proportional brake controller. Had trouble adjusting it properly after a few hundred kms, but got it kinda acceptable on the road and I will continue to fine tune the balance of brake force on the left and right wheel before our next trip.
Also installed a Hayden transmission cooler radiator to help keep the transmission from overheating. This was my major risk as left to its own devices, the automatic gearbox would shift into overdrive, revs would be too low, I would be heavier on gas, placing high load on the engine, and on the transmission. The only thing to do about this is down to driving technique.
And while I was topping up the ATF, I took the opportunity of changing 6l of the old stuff (2 drain-and-replace cycles of brown-but-likely-some-life-in-it-yet ATF) it for new, red synthetic ATF.
I also had one of those ELM357 OBD II scanners ($35) plugged into the car and the Torque app on my phone ($5, highly recommended). This allowed me to monitor the load on my engine, as well as the engine temperature (alas, no sensor for the tranny oil, but if one was overheating, chances are the other is not doing well), altitude, etc etc.
What made this trip possible is that we have the manual / auto version of the tranny on our Mazda. I drove in manual mode and made sure that the load on the engine was not >80% AND watched the revs. My torque really comes on above 2500 revs and peaks at 4000, so that's where I drove the vehicle. Mostly at around 2750 - 3000 revs which allowed me to drive in 4th at 90 - 100 kmh. On hills and mountain passes, I dropped to 3rd and revs went up to 3500, but up we went without too much drop in speed.
I also discovered that I have an overdrive in 4th gear, but that didn't affect the revs that much and much of my driving was done with it. When I did go into 5th, just to see, or on long descents (more about this later), revs dropped to 2500, then immediately to 2000 with the OD, and the load picked up significantly unless I was on a descent, so 5th gear was barely used.
I found that due to the aerodynamics of towing a boler
, I was able to go down 6% grades without using my brakes
. The drag on the trailer was enough to keep my speed in check at 100 km/h. Same on highway offramps. The drag acted as a brake assist when coming from highway speed.
I was comfortable doing 100 km/h. At points, it was easy to get up to 110, but then some stability issues crept in with the trailer (minor ones, but I didn't want them to become major ones) so I slowed down to 100.
Fuel economy was... - I'm not sure - I didn't know what to expect. In the city, we get 13 -14 l/100km (17-18 MPG) not towing, and this is what we achieved towing on the highway at speeds of 90 km/h. At 100, consumption was just over 14 (17 mpg), and at 80, closer to the 13 (18 mpg) number.
For comparison, highway driving not towing but fully laden, consumption has been closer to 7 - 8 l/100km (30 mpg) with our 2.5l 4 cylinder.
With this setup and techniques used to drive, we had an uneventful trip. Mechanically sound, engine and transmission not strained, suspension in tact, no new rattles or anything of the like. Enough speed not to be a nuisance on the road, except on the steepest mountain passes where our speed dropped to 50 - 60 - but then we were in very good company with the trucks.
We had a good trip. And many more are planned (although not of this length).