My 64 Dart 270 (automatic trans) managed 18 to 18.7 MPG while between 55 and 60 yesterday during my 800 plus mile trip home. I'm going to put together a checklist and go through each item to ensure the car is running its best. I had hoped for mid 20's. I noticed when I let off the gas to turn off the freeway, the car slowed down rapidly from 55 mph or more. It didn't seem to coast at all. I didn't hear any evidence that the brakes were dragging if they were. It felt almost like I had a high gear ratio rear in the car.

What are the specs of your car regarding: carburetion; ignition; exhaust; rear axle gear ratio; and tire size?

Thanks for the quick response. Carb is per the FSM: BBS 36805; Tires per FSM should be 6.50-13 - the car has P185 80 R13s; ignition was changed to Pertronix; FSM gear ratio for the car is 2.93. Can't confirm that tonight, but will try tomorrow.

Sorry...forgot you asked about exhaust. Has single exhaust, granted a newer one than stock. I'm hearing what appears to be a leak but haven't located it yet. I believe it is on the mounting surface of the exhaust manifold though.

While cruising at 45, downshift to 2nd and see if it downshifts.......

If it doesn't, it's not qoing into 3rd.............

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Mileage is not out of line for your setup. You can probably do a little better with careful tuning. Carburetor is 3680s, not 36805 (just for your reference) and given that it's a 1964 original, it may well be overdue for attention or replacement (you know where to go for a new one ). Tune-up parts and technique suggestions in this thread. Keep on top of the valve adjustment.

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