Adweek reports on the coming debuts of hybrid SUVs from GM and Ford.

“Everyone is entitled to play to their strengths, and ours is in trucks,” said Ken Stewart, GM’s marketing director for new ventures. “If you want to get a lot of hybrids on the road, you put them in vehicles that people are buying now. Americans like trucks more than they like small cars. So our strategy is to start with the bigger vehicles and work our way down, which also has the most benefit for society, because the bigger trucks consume the most fuel.”

Hmm. While there is something to be said for that argument—targeting high-volume vehicles with high fuel consumption—the reality of GM’s rollout is a bit different.

The new Silverado and Sierra hybrids are not full hybrids, as is the Prius, and as is Ford’s new Escape SUV. Rather, they are “mild hybrids”— they replace the conventional electric starter and alternator with a compact electric motor, which also supplies power to the transmission. There is no hybrid drive; the gas engine is always responsible for propulsion. Full-hybrid systems, on the other hand, can drive on electric power alone until the batteries need recharging at which time the gasoline engine restarts.

That’s not to discount the advantages of what GM is providing. The new hybrid pickups do use regenerative braking to recharge the batteries; they keep the HVAC system running when the engine is shut off; and they do provide external auxiliary power (four 120-volt, 20 amp outlets).

But as a result of the use of a mild instead of a full hybrid design, the overall fuel savings are less. The Silverado and Sierra hybrids will provide 5-13% better gas mileage over the gasoline models. That’s not insignificant, but it is significantly less than the 40% improvement seen in full hybrid sedans, and the 20% improvement on diesel mileage seen in GM’s own prototype military diesel-hybrid truck. The EPA pegs Silverado/Sierra hybrid mileage at 17/19/18 city/highway/combined. This is indeed a gas savings; but these trucks still are heavy drinkers.

GM is breaking ground in the US by deploying hybrid pickups, but it could do much more. (And we’ll have to see how many they build.) Full hybrid pickups and SUVs. Diesel hybrids! If it did more, then not only would the marketing argument above be accurate, GM would clearly be positioned for revitalized leadership of a more fuel-sensitive market.

Information from GM on the Silverado and Sierra Hybrids here. Information on mileage and climate change emissions of hybrid vehicles here.