Displacement isn't everything. My 87 IROC (TPI 305) got better fuel mileage than the Ford 3.8L in my buddy's Mustang. The design of the engine plays a large role in things. If there's a bottleneck somewhere in there (and usually on the earlier 60* GM V6s, the intake was the bottleneck), it will have an adverse impact on fuel mileage as well as power.

The numbers I was giving was purely highway mileage from my experience. Even my Dale Jr got right at 30 with the L67 on the highway. Bone stock, not even any exhaust mods. When I get on the highway I get up around 75 and set the cruise control. Like I said in an earlier post, 2300 RPM or so (give or take a couple hundred RPM) is the ideal cruising RPM for the 3800 motors.

 

No 2 cars are the same.When it comes to MPG's every thing from engine size,carb/efi,type of efi,trans,fwd/rwd,weight,an driving habbit. There a lot that effects mpg's

 

I think thats well said. No 2 cars are the same. I was suprised when he told me that and kinda laughed a bit but started thinking it was maybe possible. My L67 was getting about 28 when I stored it with quite a bit of in town driving so I'd say I'm satisfied with that.

 

The v6 F-Body did have a high drivetrain loss, automatic or manual didn't matter, the gearing helped the manual guys a little more not the drivetrain loss on these cars. The Monte also has roughly a 20% loss, comparing actual dyno results with crank numbers.

 

That's interesting cause the Grand Prixs (same drivetrain) average about 27% driveline loss based off dyno numbers. There's enough guys on GPONA who have dynoed their completely stock GPs that we have plenty of data to run with.