I have noticed that when I drive my moms 2004 trail blazer that has a 4.2L in it that it has a much better pick up then my blazer. If you push the pedal 1/4 of the way down you could probably peel out or close to it. If I do that with my blazer it will just get me up to 25mph at a moderate time. So how does a vehicle that probably weighs more then mine and has a "little" bit smaller engine then my blazer able to have such a better pickup? Not to mention she gets like 150 more miles to a tank of gas then I do...

 

Different cars have very different responses at initial throttle "tip-in". My '99 Blazer will easily chirp the tiresfrom a stop, but that's just how GM tends to build cars. They're fast up to 40 MPH. but not so fast after that in some cases. Also, motor size is not as important as the design and engine management. There are many cars in which smaller motors engineered for performance generate more power than larger ones.

How far any vehicle travels on a tank of gas is irrelevant to MPG. Distance traveled tells you the vehicle's RANGE, but nothing at all about its fuel economy. Those are two completely different measures. Tanks differ in size, and even tanks in the same run of vehicles can differ slightly in capacity. Run an actual mileage check by filling carefully, drive 100+ miles, then refill. Divide miles traveled by gas consumed and compare the result.

 

The 4.3L v6 is no match for the 4.2L I6 motor. The 4.3L v6 has 190hp@4400rpm / 250ftlb@2800rpm while the 4.2L I6 has 275hp@6000rpm / 275ftlb@3600rpm. That's the difference in old tech vs. new tech. The 4.3L is a 12 valve pushrod v6 engine while the 4.2L is a 24valve DOHC inline 6 engine with DIS (distributorless ignition system) and coil on plug.

Now to the weights... The 2004 Trailblazer LT 4wd has a curb weight of 4612lbs and a 2000 Blazer 4wd weighs in at 4049lbs. So the weight is definitely in the favor of the s-series Blazer, but the practically equal torque off the line and the MUCH higher hp are more than enough to put the TB ahead.

*EDIT* - thought I'd add more information about the 4.3L vs. 4.2L engine comparisons.

 

^
^
^
^
^
Ditto, and the newer I6's have even more HP.