What power?

I averaged 23 mpg in my Regal GS I used to have. I was not impressed with the mpg at all. Would think the N/A 3800 would be close to the same...

 

I prefer pedigree little champions pouches. the tenderloin is outstanding

are you talking combined mpg or just freeway? maybe it is just the ones I have seen but average 20 mpg at best.

I like the platform, one of my favorites. Are you also running premium on the GTP? if so it will not save much money really unless it is different than here where it is a 30 cent difference.

In a 18mpg highway blazer (using mine with a check engine light on for reference) at $3.69 the cost per mile is 20.5 cents per mile.

a 27 mpg GTP would be 16 cents per mile, so you make out a little there.
at 25 mpg using $4.09 (prices around here) gets you at 17 cents.

mind you there are people getting 20+mpg out of blazers. I had a 96 that would get me near 22 on the highway. that cost me 17 cents per mile highway.

I just wanted to make sure you knew I wasnt pulling it out of my backside. I used to be a 1099 worker and drove 20k miles per year. I have had to figure this all out before.

 

Most likely just the ones you have seen. Our stock Regal GS was averaging 23-25mpg, and it was easily a 28-30mpg highway car from gas station to gas station. Our modded Regal GS (3.29 gears, headers, intake, exhaust, tune) averages 22mpg with my Wife driving it. I can get a tad more because she jackrabbits the crap out of it when she drives. I've never seen someone speed up to get to a red light/stop sign more than she does. It's about a 25mpg highway car due to the shorter gears and running 500-700 RPM higher than stock at highway speeds.

Also, I apologize in advance if you've already done the calculations but the GTP, GS, and other supercharged GMs (and all forced induction cars) come from the factory with tuning tables optimized for use with premium gas. They will run with 87 or 89, but generally they have less power and lower gas mileage. As far as our Blazers, there has been plenty of threads on gas mileage. My best was 24mpg all highway. Filled up at one rest stop on the PA turnpike, cruise set at 65, filled up at another rest stop and calculated it. I average 15-16 now with a small lift and 255/70/17 A/Ts on 17x9 rims. I can still squeak out 20mpg highway if I baby it. And go downhill. The whole trip. But after over a year of calculating fuel costs and gas mileage, 89 is the best fuel for my Blazer. I actually save money with 89 over 87. Anything above 89 is a wash though.