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Old 02-25-2018, 06:42 AM   #1
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anderson , South Carolina
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strange towing circumstances "altitude-engine computer or both"

I just bought a 67 Caravel in Ok City. I picked it up with my Volvo V70, 5 cylinder wagon. At first the best I could get was 65 mph@14 mpg. Heading into Arkansas it improved to 15 mpg. In Alabama I was getting 17 mpg. Ga 19 mpg and finally South Carolina I was driving comfortably at 70 and getting 21 mpg. Cars normal MPG is 29.

Was the improvement due to altitude? I wonder if the cars computer was adjusting the mixture and other engine performance adjustments throughout the trip and finally had it adjusted by the trip end. or maybe it is just altitude.

my question is have others experienced such radical performance differences between Oklahoma and South Carolina or similar locations? Will I suffer such low performance always at higher altitudes and maybe it will be undrivable in Colorado.

also.. anyone know who sells a new or used wheel well molding for this 67 Caravel

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Old 02-26-2018, 09:10 PM   #2
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Not to be too much of a wet blanket, but I would doubt the mileage readings of any vehicle unless they were the result of pencil and paper calculations: miles traveled divided by the number of gallons used to travel those miles. Lots of things affect mileage - wind, speed, tire pressure, load on the vehicle to name a few - but you don't mention head or tail winds or hilly country which tend to affect mileage when towing. Possibly your Volvo got it 'figured out' and mileage improved along with performance. If so, hang on to that car.

1966 Airstream Caravel
2006 Toyota Tacoma
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Old 02-26-2018, 11:05 PM   #3
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There is different octane fuel in some parts of the country. We found higher octane in the East. The computer may be the issue if it was doing the calcs. The other possibility is that the extra load of towing gave your car a hot rod tune up by blowing out built up carbon. However, I kind of like the suggestion above that the car figured it out and adjusted the tune as you made more miles.

Enjoy your new trailer. Hope to see your smile down the road. Pat
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Old 02-26-2018, 11:29 PM   #4
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On board mileage displays are not necessarily accurate, as has been noted.

The on board computer doesn't take a long time to adjust, it is adjusting constantly. Getting the engine hot due to working it while towing and cleaning it out may have helped as you drove.

Altitude can play a factor, and so can the octane rating of the fuel.

But the biggest difference can be regional variations in fuel. Some regions use more ethanol, for instance, and that impacts mileage more than anything else listed. Also summer grade fuel vs winter grade fuel, as colder climates will use winter grade whereas stations in some warmer regions won't need to.
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Old 02-27-2018, 10:10 AM   #5
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Originally Posted by jcl View Post
-- snip -- Some regions use more ethanol, for instance, and that impacts mileage more than anything else listed. -- snip --.
Good point - We hunt for Shell to get their ethanol free premium to give this problem a miss. Thanks for the reminder that it's worth the effort. Pat
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