Towing with an SUV

BenK wrote:
Understand about the poor MPG on a Sequoia...for that matter most 'car' attributed
ICEs for towing heavy

They do benefit greatly with the newer close ratio with double OD automatics of
today

It really boils down to what you want vs what you are willing to accept

I keep my vehicles for decades or more...till either I can't fix them anymore
or don't want to fix them anymore...not atypical of the general towing or even
car folks

Take my Suburban as an expample of what I'll want vs accept

1996 7.4L L29 gasser. 4 speed automatic...wanted to order the manual, but they
don't offer it on an SUV, but on the pickup. 4.1 diff and about 8% larger than
stock tires (OD). F60 option, which begets 1 ton front springs (torsion bars)

Pretty much gets 10MPG no matter, but do get 12.5MPG out on pure freeway and
an occasional 15.2MPG pure freeway (wich I could figure out how that happens
and has happened often enough to claim it)

Towing 8K-10K (boat and trailers) get 6-7-8 MPG from sea level up to Lake Tahoe.
Highest pass is around 8,500 feet above sea level.

Have a 42 gallon main fuel tank and carry 5 gallon Nato Jerry cans (have four
plus three regular jerry cans and some times bring all of them)

Many here wouldn't be caught dead in a 19 year TV...but it suits me just fine
and do still drive it EXTREMELY HARD both empty (boy racer) and towing

If I keep it much longer...will or noodling a Gear Vendors in-line OD. Won't
pay for itself, but just having the convenience of having a 0.65 or 0.5 ratio
to the diff is what am looking/noodling

Since just off idle...the 7.4L has almost full torque...that extra OD will or
should increase MPG.

Image below from: Gearvendors.com
Though GM rates my 7.4L L29 at 410 Lb/Ft & 290HP
gearvendors 7.4Ltorquecurve

What the OP is asking pretty much says a full sized SUV in the 8.6K GVWR range
That means used, as no current OEM has a new one that I know of

Our friend gets 22 mpg with his diesel MB, and maxed out at 17 mpg while towing at 65 mph. Those are mighty attractive numbers, but we're concerned about the relatively low limit on tongue weight, despite a tow limit of 7500#.

Capt RonB wrote:

MargaretB wrote:
We don't have an Expedition, but I noticed that some people on the TT board seem to be towing with over-sized SUVs, and we have a friend who tows with a diesel Mercedes. That's why I was wondering if they are appropriate, and what role the torque plays in the decision.

I think engine torque plays a bigger role than most suppose. Low end torque means that an engine delivers it's highest torque at low rpm.

Take the old tugboat example. Most older tugboats had very large low HP diesels that had a very long stroke and turned very large in diameter but low pitch propellers. The high torque of these engines allowed the operator to shift from forward to reverse without stalling the engine. The massive props had considerable momentum that had to be over come when shifting gears.

The same holds for your tow vehicle. When you initially start towing from a standing start, the torque is what gets things rolling. Take two engines both 300 hp but one has torque of 375 lb/ft@ 4000 rpm and the other 375 lb/ft@ 1800 rpm. The engine with the torque peak at 1800 rpm will have an easier time starting from a dead stop and will do so at lower rpm.

Consider also how torque helps manage your towing at highway speeds. Take the same two engines cruising at 65mph on the interstate. Both Tow Vehicles are shifted into 5th gear and torque converters locked on the flat and level. When these vehicles climb a hill (say an overpass) the vehicle with the torque peak at lower rpm will be able to hold 5th gear quite a bit longer than the the one whose torque peaks at 4000rpm. meanwhile on the flat, the TV with the low end torque could be geared higher and thus cruise at lower rpm resulting in better fuel economy.

That's at least partly why diesel tow vehicles are so popular. Most diesels produce more torque at lower rpm than their equivalent sized gas brothers. Even among gas engines there can be quite a bit of variance in torque specs. I once owned a VW Rabbit Diesel all 49 hp of it. You could time it in the quarter mile with a calendar. It was slow. But man it had low end torque. It would pull my 18 foot boat, engine, and trailer loaded with gear up a boat ramp no sweat. Now I wouldn't drive it down the road with the VW but it served as a tug motor for launching and retrieving in the boat yard.

The reason most tow with bigger engines is not just more HP but the bigger the engine, the more torque.

Choose the higher torque at lower rpm for towing purposes.

FWIW check out a VW Touareg for example. Only 225hp but look at the torque! 400+ lb/ft at 1750rpm and a 7000lb towing capacity. That's better than most 1/2 ton gas pick-ups.

The drawback to this car as a TV is the fairly short wheelbase but if you want fuel economy maybe you can tolerate a somewhat rougher ride.

This is the second reason most people tow with over-sized SUVs and trucks. The longer the wheelbase the smoother the ride. Trucks and 3rd seat SUVs are generally up in the 130 inch plus wheelbase range where the Touareg is only 112 or so. The shorter the wheelbase the more the trailer will waggle the TV especially when getting passed on the interstate by a big semi.

Fuel economy is not great with the big TVs though 10-14 mpg is common. My I6 Trailblazer gets around 11mpg if I keep the speed down under 65. A gas V-8 1/2ton Pick-up might do 12 or 13 loaded the same and it might ride better than the TB due to the longer wheelbase.

This is a massive amount of information - thank you so much for taking the time to explain it all. The MB diesel has a wheelbase of 121.1" and net 398# of torque. It can tow 7500# but only accepts a max tongue weight of 600#, which is a problem for us.

We have a 2-car garage, with a Fiat in one half. So we only have room for one more vehicle, and it will function as a daily car about 90% of the time, minimum.

Our friend with the diesel MB is encouraging us - all the numbers work out fine except that it's limited to 600# tongue weight, which is way less than our trailer, which is 780#. We have two batteries and two propane tanks and are trying to figure out if there's a way to move a battery and function with one propane tank. We'd much rather drive a car around town than a truck.

MargaretB wrote:
We got rid of the Sequoia because downhill with a tailwind and no TT, we were getting between 10 and 12 mpg and were going broke.

Throwing another idea out there for you... Have you thought about maybe having a dedicated TV?

I have the Suburban for hauling and a Prius for commuting. I couldn't afford to daily drive a truck anymore. Wasn't sure it was going to work, but I've been really happy with the outcome so far.

Understand about the poor MPG on a Sequoia...for that matter most 'car' attributed
ICEs for towing heavy

They do benefit greatly with the newer close ratio with double OD automatics of
today

It really boils down to what you want vs what you are willing to accept

I keep my vehicles for decades or more...till either I can't fix them anymore
or don't want to fix them anymore...not atypical of the general towing or even
car folks

Take my Suburban as an expample of what I'll want vs accept

1996 7.4L L29 gasser. 4 speed automatic...wanted to order the manual, but they
don't offer it on an SUV, but on the pickup. 4.1 diff and about 8% larger than
stock tires (OD). F60 option, which begets 1 ton front springs (torsion bars)

Pretty much gets 10MPG no matter, but do get 12.5MPG out on pure freeway and
an occasional 15.2MPG pure freeway (wich I could figure out how that happens
and has happened often enough to claim it)

Towing 8K-10K (boat and trailers) get 6-7-8 MPG from sea level up to Lake Tahoe.
Highest pass is around 8,500 feet above sea level.

Have a 42 gallon main fuel tank and carry 5 gallon Nato Jerry cans (have four
plus three regular jerry cans and some times bring all of them)

Many here wouldn't be caught dead in a 19 year TV...but it suits me just fine
and do still drive it EXTREMELY HARD both empty (boy racer) and towing

If I keep it much longer...will or noodling a Gear Vendors in-line OD. Won't
pay for itself, but just having the convenience of having a 0.65 or 0.5 ratio
to the diff is what am looking/noodling

Since just off idle...the 7.4L has almost full torque...that extra OD will or
should increase MPG.

Image below from: Gearvendors.com
Though GM rates my 7.4L L29 at 410 Lb/Ft & 290HP
gearvendors 7.4Ltorquecurve

What the OP is asking pretty much says a full sized SUV in the 8.6K GVWR range
That means used, as no current OEM has a new one that I know of

We tow with an '05 Pathfinder. 20mpg on the highway, 15 mpg's around our crowded town, anywhere from 7 to 11 mpg towing depending on wind, terrain, and how fast I want to drive...That said, our trailer is 5000lbs gross, and well within our limits for payload, GVWR, GCVWR, etc...The MB diesel would be a decent tow vehicle for a trailer such as ours, but you have to crunch the numbers to see if it works for you....

MargaretB wrote:
We don't have an Expedition, but I noticed that some people on the TT board seem to be towing with over-sized SUVs, and we have a friend who tows with a diesel Mercedes. That's why I was wondering if they are appropriate, and what role the torque plays in the decision.

I think engine torque plays a bigger role than most suppose. Low end torque means that an engine delivers it's highest torque at low rpm.

Take the old tugboat example. Most older tugboats had very large low HP diesels that had a very long stroke and turned very large in diameter but low pitch propellers. The high torque of these engines allowed the operator to shift from forward to reverse without stalling the engine. The massive props had considerable momentum that had to be over come when shifting gears.

The same holds for your tow vehicle. When you initially start towing from a standing start, the torque is what gets things rolling. Take two engines both 300 hp but one has torque of 375 lb/ft@ 4000 rpm and the other 375 lb/ft@ 1800 rpm. The engine with the torque peak at 1800 rpm will have an easier time starting from a dead stop and will do so at lower rpm.

Consider also how torque helps manage your towing at highway speeds. Take the same two engines cruising at 65mph on the interstate. Both Tow Vehicles are shifted into 5th gear and torque converters locked on the flat and level. When these vehicles climb a hill (say an overpass) the vehicle with the torque peak at lower rpm will be able to hold 5th gear quite a bit longer than the the one whose torque peaks at 4000rpm. meanwhile on the flat, the TV with the low end torque could be geared higher and thus cruise at lower rpm resulting in better fuel economy.

That's at least partly why diesel tow vehicles are so popular. Most diesels produce more torque at lower rpm than their equivalent sized gas brothers. Even among gas engines there can be quite a bit of variance in torque specs. I once owned a VW Rabbit Diesel all 49 hp of it. You could time it in the quarter mile with a calendar. It was slow. But man it had low end torque. It would pull my 18 foot boat, engine, and trailer loaded with gear up a boat ramp no sweat. Now I wouldn't drive it down the road with the VW but it served as a tug motor for launching and retrieving in the boat yard.

The reason most tow with bigger engines is not just more HP but the bigger the engine, the more torque.

Choose the higher torque at lower rpm for towing purposes.

FWIW check out a VW Touareg for example. Only 225hp but look at the torque! 400+ lb/ft at 1750rpm and a 7000lb towing capacity. That's better than most 1/2 ton gas pick-ups.

The drawback to this car as a TV is the fairly short wheelbase but if you want fuel economy maybe you can tolerate a somewhat rougher ride.

This is the second reason most people tow with over-sized SUVs and trucks. The longer the wheelbase the smoother the ride. Trucks and 3rd seat SUVs are generally up in the 130 inch plus wheelbase range where the Touareg is only 112 or so. The shorter the wheelbase the more the trailer will waggle the TV especially when getting passed on the interstate by a big semi.

Fuel economy is not great with the big TVs though 10-14 mpg is common. My I6 Trailblazer gets around 11mpg if I keep the speed down under 65. A gas V-8 1/2ton Pick-up might do 12 or 13 loaded the same and it might ride better than the TB due to the longer wheelbase.

Good advice - thanks.

Finding a vehicle with the right combination of payload, towing weight capacity, and hitch weight capacity is a real challenge.

MargaretB wrote:
Can of worms? A question that generates informative discussion is a "can of worms"? Sorry. I had no idea.

We got rid of the Sequoia because downhill with a tailwind and no TT, we were getting between 10 and 12 mpg and were going broke. As I mentioned earlier, a friend tows with an MB diesel and encourages us to do the same. That's why I asked.

For the most part any vehicle that is capable of towing a Travel trailer will get poor gas mileage. Yes some are better than others but none are leaders in fuel efficiency.
You will need a sizable vehicle to tow a travel trailer. That in itself will lead poor fuel efficiency.
AS towing capability increase fuel efficiency will decrease.
For the record there are a lot of great gas powered tow vehicles that get 10-12 MPG when not towing.
Diesel will get better MPG's but they cost significantly more.
Unless you tow a lot or full time, buying a diesel for the addition MPG's will not be cost effective.
Buy a diesel for the additional power,torque and braking capability but don't buy it to save money on fuel.

Can of worms? A question that generates informative discussion is a "can of worms"? Sorry. I had no idea.

We got rid of the Sequoia because downhill with a tailwind and no TT, we were getting between 10 and 12 mpg and were going broke. As I mentioned earlier, a friend tows with an MB diesel and encourages us to do the same. That's why I asked.