Me Too..........

 

How accurate is my overhead liar? About as accurate as Brett Favre late in 4th quarter at the tail end of his career.

 

So you are saying that it throws a lot of interceptions and whines that nobody loves it?

 

HeHe. Yeah, I guess so, my poor overhead liar gets no respect.

 

The overhead was designed to be with-in 10% on a stock truck that has been my experience.
Now throw a programer or injectors on it and of course it will be off

 

Interesting, I'll give this a shot and see what it does.

 

The times I've checked mine its been within .3 to .5 accurate.

 

Mine is usually within +/- 1 mpg if its highway miles. Around town its usually 2.5-3 mpg high. Idle time really throws it off.

 

Mine is 3 +/- .5 mpg's higher than realistic generally but when pulling a trailer and it is reading in the 15's it is more like .5-1 mpg too high. Another interesting thing on mine is I checked the miles per gps and even with adjusting for larger tires with the Smarty the odometer was off on the low side while the speedometer was very close. I think a lot of our low reading for mpg's are because, at least on mine, I top off the tank when filling and after the thing kicks off initially I can get 4 more gallons in the tank with some patience.

The idea of just letting it go and never reseting it.....come on, sure give it 3 million miles and yeah, it will eventually come to a reasonable figure but that doesn't do any good for those of us who track it a tank at a time. Sure I figure by hand but the average mpg's over the life of my truck isn't as important at that moment as the mpg's I got on that tank. I use that to let me know when I got good fuel and bad fuel, driving conditions, possible problems with the truck and so on.

 

Mines such that deducting 1.5 mpg from overhead is ballpark correct.

 

mine is pretty close within 1mpg calculated

 

Mine was dead on when I was running the 35" tires without getting the speedo recalibrated. Well, actually it was reading just a tad lower but really close. I'll be checking it this weekend with the stock tires on it..

 

In 46 tanks of fuel since I purchased the truck in June 2008, I recorded the reading and reset the overhead in addition to hand calculating my MPG. Averaging the 2 columns on my spreadsheet, the overhead average is 16.6 mpg and hand calc is 17.0 mpg. .4 mpg low for the average. I see a few deviations: 5 tanks the overhead differed by 1-2 mpg, and 4 tanks differed by 2-3 mpg. In all but one of the nine cases where the overhead was off by 1-3 mpg, it read lower than the hand calc mileage.

It's not perfect, but a decent indicator of my mpg. In a truck like this (driven mostly in the city, and some towing 10K) I'm pleased with an overall average of 17 mpg for the 12498.5 miles I've driven it.

 

Reset ALL the setting @ each fuel stop.
Mine is usually within 0.5-1 mpg of hand calc'd.
About the only time it differs from that is 1st pull of 5th wheel, and 1st tank after towing. Then it can be off by as much as 2.5 mpg
JMHO

 

my truck is still bone stock and my overheard is off by 6 to 8mpg consistently...