lt1 and l98 are bothe good engines in their own respect if you are thinking of swapping go with an ls1 the aftermarket for the ls based engines is massive and only growing allowing for millions of engine combinations to fit your exact needs and wants all the while fulfilling them rather cheaply. If you want to know the truth the quality of the engine pretty much follows the way they came out l98 last lt1 second and ls1 first

 

Actually the L98 came out first and the LS1 last But we know what you meant, I'm just being mean.

It's the top end and cam of the motors that makes the difference. You can make as much power with a gen 1 sbc as you can with a gen 3. 15 degree heads

 

I got 30mpg on a highway cruise @70mph with 2nd passenger, ac on, and climbing different grades. I couldn't believe it. Of course I just got done getting it into 1989 level of running condition. I could never for the life of me get that good of gas mileage in my LT1, only in neutral, with the AC off, going down hill from Showlow did I get a good tank of gas.

TPi shines down low and at cruise mpgs. But we all know, they look better than any other fbody gen. Hardy har HAr!!

 

I get 15 city and 25 on the highway. Its all in the computer tuning.

 

I just got over 29 MPG highway on a trip from Philly to Columbus this past weekend. 97 LT1 M6 with a 3.23 rear and 275/40x17 tires. Stock except for K+N, Magnaflow, and PCMforless tune. I was pretty happy with that number.

 

the tune was the kicker there... I get about 16 in the city and 24 at 75 on the highway with my l98

 

I gotta call BS. No L98 GTA has ever gotten 30 mpg. They're too heavy, only come with the auto. Now a no options IROC (lighter) with the 2.77 gears, you'd still have to have one heck of a tailwind and be anorexic.

The only people that get 30 mpg are the people who have put in 6 speeds and/or do some serious computer tuning.

 

What's 42 miles divided by 1.38 gallons? 30.4 I went on a 42 mile drive with a full tank of gas, cruise control set at 70mph, AC on and a passenger. It was a loop that circled around part of my city. Had I kept driving the loop over and over, I would've gotten over 450 miles to the tank.

HOWEVER, I just went on vacation to San Diego with my brother. We were cruising between 70-80mph with little to no downshifting it averaged 20mpg. I was lucky to get 300 miles to the tank.

Under the right conditions, I was able to get 30mpg. Cry BS all you want, but its true in that circumstance.