Tow Vehicle Specs for Better Mileage
 

We made our first ever RV trip from Austin, TX to South Padre Island. Pulling a 2021 IBEX BHS with a BMW X5 with a 4.4L V8. I found that the BMW just didn't have enough torque to be able to keep itself in its highest gear. Only in high gear would my instantaneous mileage gauge go over 10 MPG. This first trip, we averaged 7 MPG. At 282 HP and 324 ft-lb of torque, I think it just doesn't have enough power to keep itself in the sweet spot it needs to be in order to perform at it's best.


I've been looking at used Tahoes or Yukons. Does anyone know how well these would do as a tow vehicle for this size trailer? What HP / torque minimums should I restrict my search to? My initial thought was to not consider anything less than 300 HP and 350 ft-lbs of torque. What do you think?

Gas tow vehicles pulling a full height travel trailer, will always get 8-11mpg average, depending on various conditions.
So if you're wanting higher mpg than that, get a diesel or a folding trailer.
A Yukon or Tahoe will be fine as long as it has the full factory tow package. An HD package would be better.
With SUVs, look at the Payload Capacity on the driver's door frame. Make sure it has enough for the weights of the trailer's loaded tongue weight, everyone in the car(including the driver), cargo in the car and the WDH.

Bikendan is right.

It takes X energy to move X weight and the slight variances in efficiency between different gas motors is like chasing snipe. (anyone torture kids with that one anymore?)

The best you can do for mpg's is slow down to remove the wind drag.

Your BMW does seem a little light in the britches for what your towing and expect. You're running out of torque due to your horsepower and your tall gearing. A properly equipped Tahoe (as stated by Bikendan), will handle your TT and provide you with more torque, but resign yourself to the fact that with a gasser you're not going to be able to stay in "high gear" all the time. The Vortec engines in the Tahoes and Yukons cruise at about 2200-2400 rpm. Very little HP and torque in that range. Those engines produce their optimal performance in the 4000-4400 rpm range. Granted, you won't see this range unless you're pulling a mountain pass, but you will see the 3400 range on downshifts. The downside to most of the Tahoes and Yukons is that they come standard with 3.08 (GU4), gearing for fuel efficiency. This means you have speed at lower rpm, but no torque.

When you're not towing, do you want to drive the BMW you already own or a Tahoe that you'll have to buy? The bit of mpg you could see while towing would be a plus, but probably not enough to pay for buying a Tahoe.

Pick your TV based on what you want. Perfectly fine but less than optimal towing capability can easily be offset by other things, and awesome towing capability can come at a price you don't want to pay on your regular commute- and that's before you spend to buy a different TV.

You’re not going to do much better in a gasser. When I tow, my TT weighs 6,500 lbs loaded, (GCWR 12,500 lbs) and I consistently average 9.5 mpg (Durango with 5.7 V8 has 360 hp, 390 torque). I had considered Tahoe/Yukon but wanted a longer wheelbase.

Dry Weight 4,626 lbs
GVWR 7,474 lbs
Cargo Capacity 2,848 lbs
That's a pretty big load on an X5. Drop it down a gear and slow down, keep it below 60 mph to keep your mileage up. You would be amazed at how much air you are pushing.
The 2019 BMW X5 offers 6,600-7,200 pounds maximum towing capacity.

Average is about 8 with a gasser. If you like the BMW keep it.

This really makes me wonder what the X5's payload is. The listed hitch weight for the trailer is 510....the reality hitch weight is likely closer to 750ish. With the weight of the hitch itself, I'd be surprised if the X5 had 300lbs remaining payload.

Looking at a similar sized SUV, our '20 Toyota 4Runner has a payload of 1165 and only rated to tow 5000lbs. This has a 4.0l V6 but the vehicle is built more like a truck with body on frame construction.

Sorry for my ramblings...my point is that I bet with the actual tongue weight, driver and trailer hitch on the X5, it's overloaded.

Something not mentioned is the Mfr's instructions for towing a trailer. What do they say for the BMW?

Some manufacturers recommend that the "top gear" which is usually an overdrive, not be used when towing. It's often recommended to stay in the next lower gear which is usually a "direct" gear which both takes strain off the OD gear, increases available torque, and lessens the heating effect in the torque converter.

As mentioned above, slowing down also improves mileage. I watch my mileage and just slowing from 60 (our state's legal towing speed) to 55 mph makes almost 1 mpg difference.

You'd be amazed at how much company I have over in the RH lane at that speed too. :cool:

check on a tuner . dlnt run in o.d.

If your vehicle has a "tow mode" switch, use it. It typically optimizes everything by adjusting the shift pattern. MPG will be horrid, but that's the way it is.

While 7mpg is a little low, lots of factors come into play on buying a new vehicle for towing.
Is it a preferred daily driver?
Is it near paid off?
To repeat what others have said, SLOW DOWN a little, wind resistance IS the mpg killer.
That said, now figure out your towing miles per year versus the cost saved by a few MPG gain with the cost of the new vehicle.
More people go RVing less each year after initial purchase vice equal or more time camping. Sad but true.
I read where several gain mpg by locking out overdrive gears.

I agree.

The biggest problem with any vehicle's "Tow/Haul" mode is the operator. People are always trying to outsmart a system designed to do a certain task...and it likely does it well, just not to the operator's liking/expectations.

Case in point, the OP wants the best MPG, using the highest gear, all while dragging a trailer that acts as a 7k pound anchor on the back of his vehicle.

Every action has a reaction and attaching anything to the rear of your vehicle that essentially doubles (weight) the workload for the engine will have negative effects. In this case, MPG suffer.

Consider picking up a used diesel VW Touareg. Good towing capacity (7700), good handling and good mileage when towing. Lots of posts on internet by individuals towing with a diesel Touareg.

Our specific case might illuminate the mpg while towing issues a little better:

A122 A-frame towed by Hyundai (Kia) minivan - trailer was not quite as high as the minivan (60" high), 65mph tires:

• at 65mph, low altitude (less than 2K): 17mpg, as low as 14mpg in 20mph headwinds
• at 65mph, high altitude (greater than 5K): 19mpg, as low as 17mpg in headwinds, as high as 21mpg with tailwinds

A213HW A-frame towed by same minivan - trailer is higher than minivan, 7" higher when folded (67" high), 75mph tires. Trailer is 300# heavier as towed than the A122:

• at 65mph, low altitude: 14 mpg
• at 72mph, low altitude: 12 mpg
• at 75mph, low altitude: 11.0-11.5 mpg, as low as 10.0mpg observed in sustained headwinds
• at 65mph, high altitude: 14.5-15.2 mpg
• at 72mph, high altitude: 13mpg
• at 75mph, high altitude: 12.0-12.5 mpg

A couple of notes - wind resistance falls off faster with altitude than power does on a normally aspirated, fuel injected engine. As a result, it is just as easy to tow at high altitudes, as it is at low altitudes at higher speeds. Fuel mileage benefits from BOTH reduced power available and reduced air resistance. The only time altitude really affects performance is climbing steep grades.

Air resistance is much more significant with a full-height TT. Lucky for me, we are limited to about 7ft by the garage door.

hope this helps
Fred W
2019 Flagstaff T21TBHW A-frame (same as A213HW)
2008 Hyundai Entourage minivan (250hp, 240 ft-lbs torque, 230K miles)
camping Colorado and adjacent states one weekend at a time

Towing capacity is only half of the equation. As clarkbre stated in post #9, the unladen tongue weight of the OP's TT is 510 lbs, and 750 lbs is a good ballpark figure when TT is loaded. I seriously doubt the Touareg can handle that.

Yukon XL
 

We used to tow our tracer 20RBS with a Jeep Grand Cherokee and usually got around 10- 11 mpg.
After switching to a Yukon XL with the factory tow package, our mileage went up to 12 mpg. Payload was increased by 400lbs too.
I'm glad we switched, it's just too much for the smaller framed mid size SUV's

The OP said the IBEX BHS, so I am presuming it is the IBEX 20BHS, which way too much trailer for his current tow vehicle. I towed a similar trailer with my 2014 Tahoe. The TV had the Max Tow package (5.3L V8, 6-speed tranny, 3.42 differential). The sweet spot towing ran between 2200 - 2400 RPM (as stated). At 63 mph it averaged 8 mpg towing (9-10 mpg on flat country and 6-8 mpg in rolling country; 4-5 mg in the mountains). It was a little slow on long, steep grades but did well. It was, however, at the limit of its tow abilities.


I would suggest that you look at crew-cab pickup trucks for that rig. Better handling, more power. I currently tow this sort of trailer with a 1500 Silverado with a 6.2L, 8-speed & 3.23 differential. Tows great & gets 10-14 mpg on the flats and 7-10 mpg in hilly country but has plenty of power. Typically runs at 1850-2000 rpm over flat country and 2200-2400 rpm in hilly country on grades. YMMV.

Looks like a X5 4.4 has a 6,008 lb GVWR with a curb weight of 4,960 lbs. So payload would be approx 1,040 lbs.

If 750 lbs tongue weight is accurate, vehicle is probably over GVWR. I agree, a Touareg isn’t going to be any better.