16V fuel economy

[Reaper1]

I am on a massive moving road trip and we are driving the 16V TC (hard top on) and my '90 V6/5spd Daytona. Both cars are VERY loaded down and they are getting almost exactly the same fuel economy...right at 30mpg at about a 60mph pace. This is going up and down the Cascades and Rocky Mountain passes, too.

 

For comparison, my 8V/automatic TC got something like 24mpg on a similar trip averaging 72mph with the top down most of the way. 

 

Just thought that comparison would be interesting to some folks.

[Hemi Dude]

The 8 valve engine with the 3 speed automatic gets the worst fuel mileage of the 3 various engine/transmission combinations.

My 8 valve TC with the 555 5-speed gets 32 - 34 MPG regularly on a road trip.

At 72mph, your 8v/automatic is also twisting over 3,000 RPM.

[Plumbinguy]

I'm twisting 3000 rpm's @ less than 60... That's the one thing I think is not right with my car. 8 vlv 3 speed automatic. Any thoughts?

[Reaper1]

Yeah, so when I drove my 8V on that trip a few years ago I found that anything over 72mph and the engine was always in boost and sucking down gas. I think I got 17mpg on one leg because I tried to go the speed limit (80mph)! 

[Reaper1]

8 hours ago, Plumbinguy said:

I'm twisting 3000 rpm's @ less than 60... That's the one thing I think is not right with my car. 8 vlv 3 speed automatic. Any thoughts?

Sounds like the tach is off, honestly. If it truly is winding up that hard, are you SURE it is getting into 3rd gear? 3000rpm should be right around 70mph.