DeserTBoB wrote:
> Those who read what I did to my '86 Fifth Avenue may find this
> somewhat interesting. I just took a 678 mile road trip to northern
> Nevada via US 395 in the car, using cruise control, AC about 40% of
> the time, speeds at posted limits not exceeding 65. Average max road
> speed: around 62 MPH.
>
> Vehicle/drive train: '86 M-body, LA roller cam 318, Holly "Carter
> clone" 6280 feedback carb., A-904 trans with lockup converter. Basic
> timing: 7° BTDC @ 630 RPM per California spec. Fuel: 87 average
> octane "regular."
>
> Trip plan: Lv Lancaster CA via north CA 14 to US 395 to the Nevada
> state line at Topaz Lake and return. No local driving at destination
> (just bicycling around the lake), no idling with AC on, no "warm up"
> idling, etc.
>
> Elevation at start and destination: 2580 and 5950 ft above sea level.
> Maximum elevation: Conway Summit, 8130 ft. Route has three major
> 6-8% grades northbound.
>
> Fuel economy going: 25.4 MPG
> " " return: 28.9 MPG
> Average: 27.2 MPG
>
> All CA smog gear is working as per spec., as well, with no
> disconnected EGR or other illegal mods.
>
> The best mileage ever from this vehicle was a trip from Laughlin, NV
> to Barstow, CA: 29.1 MPG, average max speed 55 MPH.
>
> I think it's fixed. Why do newer, smaller models with V6s get worse?
> One can only ponder, but the answer always comes back the same.

The '99-'04 M body cars would do better than that. I know my Concorde
would. It gets 26-28 on its daily 80 mile commute, 31-32 on non-stop
highway.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')