Home Travel Stories Gas Logs 1979 FORD F250 Custom Explorer 460-4 bbl MPG= 6.4 Overall
1979 FORD F250 Custom Explorer 460-4 bbl MPG= 6.4 Overall PDF Print E-mail
Written by Double Dragon
Saturday, 03 December 2011 22:36

1979 FORD F250 Custom Explorer 460-4 bbl MPG= 6.4 Overall

oneownercollectorcar.com

Story and photography copyright by D. S. Brown.

79-ford-f250-custom-karl-gas-gauge

Metric= 7.5 L engine- 36.8 L/100km Overall

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MPG of the Ford F-100 series pickups when new= 11 MPG City (351 cubic inch engine)

The 1979 EPA figures use a dynamometer to reproduce 70 degree F temperatures on flat dry road conditions in a well broken in vehicle. The 1979 EPA test dispensed with the the CITY, HWY and COMBINED categories. Instead the 1979 EPA 'Estimated' mileage reflects City driving in stop and go but not gridlock conditions.

The EPA Gas Mileage guide tested a 351- 2 barrel 1979 Ford F-100 with a 3 speed automatic which comes as close to the OOCC truck as we can find in their tests. When the 351 was equipped with a manual 3 speed mileage jumped to 13 MPG. The mild lower end F-100 truck is a much different animal than the OOCC monster 460 F-250 featured in this story.

The lesser engines available that year improved mileage in the F-100. The 300 cubic inch six cylinder with a single barrel carburetor gave 16 MPG with automatic. A 3 speed manual bumped it up to 17 and the four speed manual managed 18.

The 302 in 2 barrel form managed to scrape 14 MPG out of the 1979 F-100 truck with a 3 speed automatic. Once California's extra emissions equipment was added in the MPG dropped to 13. MPG jumped to 15 with the manual transmission regardless of whether it was a 3 or 4 speed.

Comparing the pickup to cars using the same popular Ford engines gives an indicator of just how much the truck's tall profile, blocky wind blocking shape and extra weight factors into mileage potential. The square tall truck forces the 351 to work very hard to push through the wind.

The 351- 2 barrel running through a 3 speed automatic provides 13 MPG hauling the significant weight of the 1979 Ford LTD Station Wagon around. That's 2 extra MPG above the F-100 using the same drive-train. Curiously, the 302- 2 barrel with automatic in the LTD only manages 14 MPG which equals the F100 using the same drive train. The LTD passenger car bodystyle adds 1 MPG to each  figure due to less weight and better aerodynamics with 15 out of the 302 and 14 from the 351. The 302 coupled to an automatic makes it all the way up to 16 MPG when dropped into the small light Fairmont body.

Things become confusing with the 1979 Mercury Marquis Station Wagon. It returns the exact same figures using the 302 drive-train but jumps to 15 MPG with the 351. It seems that the 3 way catalytic converter with feedback on the Marquis is somehow responsible for this unpredicted result. There is also the known fact that a bigger engine doesn't work as hard as a small engine hauling a heavy car around which has turned up frequently in the GAS LOGS. The passenger car version of the Marquis gets 15 MPG with either 302 or 351.

An interesting detail from the 1979 EPA guide is the cost of gas back then. The EPA made their calculations based on 70 cents per gallon (Diesel was 60 cents). They also made the assumption that the average American drove 15,000 miles annually in 1979. In the 1960s annual driving was often estimated at 10,000 to 12,000 miles.

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OOCC Ford F250= 6.4 MPG overall

With a 460 cubic inch engine drinking through 4 barrels and winding at high revs from its 4.10 axle you can't expect good gas mileage. Add in the high profile wind fighting shape of the truck plus its sheer weight and the overall 6.4 MPG is inevitable. The truck was also using the new 10% ethanol laced unleaded fuels available in 1979 which provide less energy than leaded high octane fuels without ethanol which were available in the 1960s.

These figures chart the MPG of the truck from the instant it was driven off the Sound Ford car dealership lot Oct 6, 1979 with no mileage as a brand new truck. As the engine breaks in, mileage should improve as tolerances increase, rough edges are shaved off and things loosen up a bit. See the story about this truck in the ONE OWNER section of CAR STORIES on this website. Here is the cover of the little log book that original owner Karl used to document the first few years of ownership of his truck.

79-ford-f250-custom-karl-gas-log-1

The truck was initially bought for a move to Ferndale, Washington from Kent, Washington a distance of 115 miles each way on a good highway. The move was done in late fall/ winter when temperatures hover a few degrees above freezing and it rains heavily. Obviously, the truck was carrying heavy loads during the move. Karl built a wood lumber rack on the back of the truck which increases wind drag, diminishing the slipperiness of the already non aerodynamic truck. The truck returned 7 MPG during the steady highway driving. The truck dropped as low as an amazingly thirsty 3.1 MPG when it was being used to transport lumber, rocks and bricks short distances. The absolute highest mileage the truck ever managed was 10.6 MPG.

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Karl maintains his truck according to the recommendations of the manufacturer, so his tire pressures were close to the listings suggested above which call for 35 front and 55 PSI rear when the truck is carrying its maximum load. High tire pressures help ease the rolling resistance which aids gas mileage. The large 16.5 inch diameter rims have high profile tires mounted which creates a large diameter tire. The door jamb label is reproduced in full except for the final significant portion of the VIN.

Odometer Gallons   MPG (uncorrected)
75        28.2     N.A.
201      16.2     7.7 MPG
296      12.6     7.5 MPG
396      14.3     6.9 MPG
495      13.6     7.2 MPG
545      16       3.1 MPG
628      18.8     4.4 MPG
857      16.2     Not filled
987      20       6.5 MPG
1,156    27.1    6.2 MPG
1,266    12       9.1 MPG
1,416    14.1   10.6 MPG
1,525    11.5    9.4 MPG
1,675    29.5    5.0 MPG
1,772    13.5    7.1 MPG
1,875    15      6.8 MPG

Total number of gallons 278.6/ total miles 1,800

1,800 divide by 278.6= 6.4 MPG

Total of individual MPG entries is 97.5/ divide by 14 entries= 6.9 MPG which is close to the overall math. After becoming discouraged about the lousy mileage, a brief return to record keeping was attempted at 3,000 miles as seen below. Mileage was still down in the dumps.

Odometer Gallons  MPG (uncorrected)  
3,036   25.1    N.A
3,163   16.8   7.5 MPG

Below you can see the log book with the headings for gallons, cost and mileage. The headings marked 'grease/ parking' were actually used to list the date.

79-ford-f250-custom-karl-gas-log-two

Karl discontinued his logs after 1,875 miles and then resumed with a few entries after 3,000 miles. It's a good idea to monitor your MPG once you have established the operating costs. A sudden drop indicates a problem with state of tune, a low tire, dragging brake etc. In this case after determining the truck's baseline for the first 1,800 miles, Karl lost interest in monitoring his truck after a few fills at the 3,000 mark because it was too depressing to think about the abysmal MPG!

30 years later, a 2012 Ford Econoline E250 Super Duty van produced exactly twice Karl's MPG figure. This van was powerful and large with massive payload carrying capacity, yet only packed a 281 cubic inch engine. See the story in these GAS LOGS.

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Last Updated ( Wednesday, 09 April 2014 00:35 )