Overhead accuracy

[CJEliassen]

I did some testing on my recent trip to Reno. I made several fill ups and drove at varying speeds and discovered the overhead is more accurate at slower speeds.

Overhead Hand Calc

55MPH 22. 2 22. 3

60MPH 21. 1 21. 3

65MPH 20. 5 20. 7

70MPH 19. 1 19. 4

75MPH 17. 5 18. 1

80MPH 16. 0 17. 2

85MPH 14. 7 16. 0



Anyone else notice this as well?

 

[PaulG]

now did you sit in any traffice or do any excessive idleing? that would change things alot also

 

[CJEliassen]

Highway on to highway off. And if it is more accurate at slower speeds, then it might be possible to assume at idle its perfectly accurate. It reads 0. 0 when I reset the computer and I am not moving at idle. Thats 100% accurate! LOL

 

[klenger]

Those are good numbers in any case.



One thing I have noticed with the overhead computer in my truck is that once it establishes an average MPG reading at the beginning of the tank, it seems to be very reluctant to change the average much if you change the driving conditions.



Example: If I refuel and reset the computer and drive 100 miles empty, and then hook up the trailer and drive another 100 miles, the computer keeps a higher than real average. If I refuel and rest the computer and tow for the first 100 miles and then drive empty for the next 100, it keeps a lower than real average.



My actual milage towing for a full tank is almost always higher than the computer.

 

[WMcGuire]

We just returned from a 2400 mile trip to Ft. Stevens in Oregon, beginning with 2800 miles on the odo pulling a 19' TT, CC generally set at 62 MPH, 1800 RPM approx. Napa CA to Eureka, overhead registered 12. 5 mpg, Eureka to Gold Beach, OR, overhead = 12. 7, Gold Beach to Florence, OR = 13. 1, Florence to Astoria, OR, 13. 5, Astoria to Salem. OR = 13. 9, Salem to Grants Pass, OR = 13. 8, Grants Pass, OR to Lodi, CA = 14. 1, Lodi to home = 13. 6,

Those were all accumulated miles ending with 5285 miles on odo, the first 500 miles were mostly towing and seem to average around 12. 5 mpg, after that it was combination of towing and touring (w/o trailer), the most dramatic changes were when driving empty and the last leg of the trip when going over Pacheco Pass on hwy 152, the mpg on the overhead dropped from 13. 9 to 13. 6 in about 3 miles, total hand calculated mpg for the trip was 14. 22 mpg, at this point I don't see that the overhead has any real useful function other than providing a distraction for those who have a need to fret about something, I have found also that I can get great mileage (over 22 mpg) by resetting the overhead just before going down a long hill!!