GM's I-6 Has Dual Personality

At a time when many automakers are shedding their inline 6-cyl. engines, General Motors Corp. is pulling full speed ahead with its new all-aluminum I-6 engineered for its redesigned family of midsize SUVs — GMC Envoy/Chevrolet TrailBlazer/Oldsmobile Bra-vada.

The new 4.2L DOHC 270-hp powerplant, mated to a Hydra-matic 4L60-E transmission, moves these trucks as smoothly and quietly as if they were midsize cars instead of rugged vehicles pushing a curb weight of nearly 5,000 lbs. (2,300 kg). If you didn't know better, the engine's ready torque could fool you into thinking it was a small V-8.

Impressed by the I-6's softer side, I wanted to see how it performed in utility mode. In particular, I was interested in how it compared with my Jeep Grand Cherokee's long-in-the-tooth-but-still-dependable 4L I-6.

So I took the Ward's test-model TrailBlazer home for the weekend and used it to tow our family's Sea-ward 25 sailboat from its berth on Lake Erie on the Ohio border to its winter quarters at my husband's flying club northwest of Ann Arbor, where it will be stored in a large airplane hanger among a gaggle of soaring planes.

The Vortec I-6 did a yeoman's job in the 100-mile (160-km) trip, never breaking a sweat, despite not having the recommended towing rear-end gear ratio. Combined weight of boat and trailer was about 5,000 lbs. Following the manufacturer's recommendation, we traveled the freeway portion of the trip at 55 to 60 mph (88 to 96 km/h) in third gear. The rpm consistently stayed in the 2,000 range. Outside air temperature was in the 60s, and the coolant temperature never exceeded the normal level.

GM is pleased enough with its I-6 that it reportedly plans to roll out I-5 and I-4 versions. There's still plenty of worthy competition. BMW uses inline engines in its 3-Series, two of which placed in this year's Ward's 10 Best.