Can you have your full-size SUV cake and eat it too at a time when pundits are hinting at $1.50/litre this summer for gas?
General Motors, in conjunction with Chrysler and BMW, is working on what is called a 2-mode Hybrid System currently found in the GMC Yukon and Sierra, Chevrolet Tahoe and Silverado and Cadillac Escalade.
This is a “full” hybrid system in that it can operate on electric power, gasoline power or a combination of both for a claimed saving of up to 25 per cent.
While the GM Hybrid system is one of several affordable hybrid technologies, it is the most capable for large vehicles. In fact the 2-mode hybrid system was adapted and refined from the 2-mode hybrid technology GM has used in city buses since 2003. It is now the first hybrid system used in a full-size SUV.
The Hybrid’s drivetrain is the sum of three main components, each of which works together to provide seamless, economical and comfortable operation that goes virtually unnoticed by the driver and passengers. The components are an Electrically Variable Transmission (EVT), an Energy Storage System (ESS) and the Vortec 6.0-litre Gen IV V8 engine with Active Fuel Management (AFM) that allows it to run on only four cylinders under light energy demand situations and late-intake valve closing (LIVC)
At all times, the 2-Mode Hybrid system collects torque-based data, deciphers it, and then determines the most fuel-efficient means of propelling the vehicle. It can operate in infinitely variable gear ratios or one of the four fixed-gear ratios.
This results in a number of ways to save fuel such as: engine off at idle; electric only propulsion to 48 km/h in light load conditions; electric boosting during acceleration blends with engine power to save fuel; cutting off fuel to the engine during vehicle deceleration; active fuel management cylinder deactivation technology; regenerative braking and engine speed and load control.
GM claims no other hybrid can offer the fuel efficiency improvement along with the full-size utility of eight-passenger seating and towing capability of over 2,700 kg (6,200 lb).
Tested here is a 2008 Tahoe four-wheel-drive hybrid that lists at $69,125 and includes a host of standard features like tri-zone climate control, cruise, premium ride suspension, StabiliTrak stability control with proactive roll-over avoidance, four-wheel disc brakes with ABS and OnStar with turn-by-turn navigation for a year and a bunch of other things too numerous to mention.
To this was added $3,325 worth of options like overhead DVD infotainment system, rear-view backup camera and Bose premium sound system for a grand total of $73,810 including $1,250 shipping.
I mention this to point out that nothing one  expects  in  terms  of comfort, utility and capability in a full-size, fully loaded SUV is sacrificed to engineer in the 2-mode components.
The Tahoe incorporates GM Autotrac automatic 4WD system, which lets the driver select 2WD, AWD, 4WD high and 4WD low at the twist of the rotary knob to the left of the steering wheel.
The 6.0-litre V8 in the Tahoe Hybrid produces 332 hp and 367 lb/ft of torque with 221 lb/ft of torque from the system’s electric motors.
But the core question is can this big truck really deliver what GM claims?
To test it fully, I started with a full tank of fuel and drove on a wide range of roads from gravel in the country, suburban side streets, two-lane highways and super highways.
Staring the Tahoe Hybrid does not mean the typical rush of the gasoline engine churning into life, but it comes to life with more of a bump as the 300-volt battery kicks everything into life.
On the dash upper left is a small eco gauge with a green band in the centre. The idea is to keep things in the green band — which means optimum efficiency. Use the brakes and the needle swings to the left, meaning the battery pack is being fed regenerative energy. A swing to the right means there is an energy draw and that comes when the engine is being taxed. The higher the speed or acceleration, the further the needle goes to the right.
But the big one to watch is the centre tachometer. When you stop, the tack needle drops to the Auto Stop position, meaning you are operating on full battery. If you hit the gas, the engine starts immediately and launches the Tahoe forward. But once you get the hang of pushing lightly on the pedal, the Tahoe moves off under battery power and you can travel along quite nicely at up to 48 km/h. Exceed that and the engine cuts in.
At the bottom of the tach is the driver information centre that gives all kinds of useful stuff like oil life, tire pressure and outside temperature.
But it also gives instant and average fuel consumption, and as a bonus, it also lets you know when you are operating in the four-cylinder (V4) or V8 mode.
Driving down to London, to help my daughter move out of university residence, I found that if I set the cruise at 100 km/h it would easily stay at V4 operation and gave me 9-11L/100 km at around 1,500 rpm. At 80 km/k on a lesser highway I saw 8L/100 km at 1,300 rpm. The longest I went on full battery was 12 km on a gravel road at 40 km/h
Now Hwy. 401 was a challenge and no one goes 100 km/h even in the right-hand lane. You simply are on and off the cruise so much that you sometimes have to travel in V8 mode and feel the pain of 16-17L/100 km.
But at roughly a half-tank I had covered 403.9 km and used 52.1 litres of fuel. Best of all, my average fuel consumption dropped from an indicated 14.3L/100 km when I picked it up to 13.2L/100 km.
And the end of my journey I had covered 672.5 km, used 86.1L of gas and my average was down to 13.1L/100 km.
According to Energuide Canada the Tahoe Hybrid has a fuel rating of 10.5L/100 km (27 mpg) city and 9.8L/100 km (29 mpg) highway so I was pretty close.
Filling the tank back up cost $113.93. Yikes you say, but consider this.
Assuming I had the truck from new and assuming I worked at maximizing fuel economy, at $1.20/litre (the day I drove it) on the highway cruising at 10L/100 km 100 means it cost me $12 to go 100 km. If I was doing 17L/100 km it would have cost $20 ($20.40 actually) to go 100 km. So over the entire trip, I saved $8 every 100 km or about $53. Add that up over 10 years and it’s something to think about.
Of course I know a full size 4X4 is really not the most environmentally friendly, or perhaps even acceptable, vehicle in the current rising gasoline climate, but it sure beats any non-hybrid SUV out there.
So to answer the question, can you have your full-size SUV cake and eat it too? The answer is not yet, but the 2008 Chevrolet Tahoe Hybrid is on the right road.


CHEVROLET TAHOE 2-MODE
HYBRID 4WD 2008 AT A GLANCE
BODY STYLE: Full-size SUV.
DRIVE METHOD: front-engine, four-wheel-drive
ENGINE: 6.0-litre, DOHC V8/electric motor (332 hp, 367 lb/ft; 221 lb/ft from electric motor)
FUEL ECONOMY: 10.5L/100 km (27 mpg) city; 9.8L/100 km (29 mpg) highway
PRICE: $69,125; as tested, $73,810 including $1,250 shipping fee.
WEB: gm.ca