Ultragauge accuracy

Who all believes their ultragauge numbers? Mine says I'm at 19.1 mpg. Math says 17.8. Filled the tank up right after initial setup, so basically one tank +/- 4 miles difference between ultragauge setup and trip meter. Also the ultragauge is 3-4 mph faster than speedometer. Fuel level seems to be pretty close.

 

You have to calibrate it to the tire size. Its not just plug in.

 

Garbage in garbage out. UG is ultra hyped. Just do the math the old fashion way.

 

There's nothing wrong with the ultra gauge, it works well and is a great tool, but you have to calibrate it first. Both the miles and the mpg end to be calibrated, just follow the directions in the manual. Mine was telling me I was getting 20 mpg's until I realized I hadn't calibrated the mpg gauge correctly. Now it's spot on.

 

Feel like an idiot...

 

If you REALLY want it accurate, be sure to calibrate for distance. Probably similar to my ScanGauge - do a 50 mile run by mile markers, and adjust the % based on the difference between your UG and what the mile markers say. This is more accurate for mpg than basing it on miles per hour. Be prepared for some error in fillups, unless you fill to the very top, which many do not recommend. I do it a couple of times a year, to adjust for tire wear, but always on a road trip where I'm burning 2-3 gallons right away. No charcoal filter problems.

 

Mine has always been within +/- 1MPG. I love it and all the different gauges it displays.

 

It's very accurate. I have calibrated mine over a distance of 300 km with GPS and after with 3 full tanks. When I fill up, I'm pretty much always within 1/8 gal. from what my Ultragauge says in terms of fuel usage. Speed is pretty much dead on with GPS too.

 

I have had mine in 2 different vehicles and so far it works just fine. I usually calculate my MPG at the pump also and the average on the UG is usually 1mpg more than I actually get. I think the main difference is when it jumps to like 99mpg when coasting down a long hill or up to a stop sign.

 

You fill to the very top to adjust for tire wear?

 

if you want accuracy...

you need to calibrate speed in coordination with GPS if you want accurate speed
if the ultragauge allows it

--
and for accurate MPG you must calibrate each and every fillup and use the same pump
vehicle facing the same direction and stop filling at the first autoshutoff click

scangauge allows both calibrations, [UG should too... but if not, then UG is garbage]

 

The only option that I'm aware of that the UG doesn't have that the SG has is a EGT gauge (so hardly garbage). Although it would be nice to have a EGT gauge I don't really tow anything so it would be pretty much wasted on me. Not worth paying twice as much for one gauge IMO. Nothing wrong with the SG at all and I like it. Just not the price for one extra useful gauge.

Plus I like the size of the UG and how it looks compared to the SG but that is a matter of opinion.









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About every 6 months, depending on how many miles driven since the last time I calibrated it. Over 37,000 miles, my OEM tires lost 1/2 inch tread, ie a full inch in diameter, which of course changes the distance traveled in revolutions per mile. Noticed it when mpg dropped after new tires mounted. I calibrate my ScanGauge for distance accuracy, really don't care that much about speedometer/miles per hour. On a regular trip I make a couple times a month, the SG odometer function is spot on for 50 miles. Truck odometer reads about 2.5 miles higher - this is with OEM size Michelin LTX MS2's. So, I'm checking the same trip to see how much the odometer error changes as the tires wear. With odometer error = zero, the only other data error I'm aware of is difference in fuel quantity on fillup, which I hope to minimize by resetting the SG fuel adjustment factor a couple of times a year. SG fuel used is very, very close to what the pump reads on fillup.

 

Okay, I think I understand all that you just said, my brain isn't functioning properly today. Still feels like morning to me. But I still don't understand why you need to top off for fuel accuracy? Why do you need 21 gallons in the tank as opposed to 18? (Or whatever the shutoff difference is, usually a gallon for me) Thanks.

 

Objective is to make sure the gauge (ultra or scan) is calibrated accurately for fuel. So, once or twice a year (usually 2 fillups back to back), I fill the tank to absolutely all it will hold. On the second fillup, I adjust the gauge fuel % error to reflect the difference between what it holds and what the pump says. The problem with full fillup is you can have charcoal canister problems, but when I do it, it's right before a road trip where I'm burning 3-4 gallons right away. The biggest errors I've seen with the SG can be related to variances in fueling, ie a pump may have higher pressure and cutoff sooner than another pump, it's really a crap shoot whether or not you are really filling the tank to the same level every time you fill up. To be honest, my truck will take 2.5 more gallons from when it automatically shuts off.

 

I understand now, I think. Maybe it's because I don't have a gauge yet. But when calculating MPG I try to use the same pump and let it auto shut off, is that reliable? Or do you think even the same pump gives different shutoffs?

 

I use the exact same pump and fill it up till the first shut off. I've done this since I've had the UG with the exception of being on vacation.

I did a test one time and filled it all the way to the neck (I know not recommended) then ran it out and wen't back to the same pump and filled it to the neck once more. The MPG was +/- a little less than one MPG. Not bad in my opinion. Now... I don't recommend doing this as it can screw up your evap. system but that way I truly knew what I was getting real world (hand calculated) and what the UG was saying. Is it perfect every time? No. But it is pretty damn close and the instant MPG helps me keep my foot out of the throttle.

All in all a good investment IMO.

 

Thanks for the explanations. About to buy a UG from a TW member. I like to keep the money within the forum!

 

IMHO
there is no good way you can be accurate with this method unless you tilt the vehicle fore and aft 15 degrees...or get on the tailgate and shake the bejeesus out of it while pumping.....your air bubble at the top of the tank will vary. it is much more accurate to do one of the below

a) measure and weigh your gasoline (most accurate, no one does this except at the track)

b) use same pump, same temp, same direction, stop at first click. this is the best you can get

 

I do this to manually calculate MPGs at half tank mark.