Biggest MPG error you've seen on your uncalibrated gauge? (Nissan X-trail SG/UG)
 

How about 40%?

My brother recently replaced his Honda Ridgeline with a Nissan X-Trail (predecessor to the Rogue, not sold in the States). Went from...

• 3.5L V6 AWD automatic (Honda), to...
• 2.5L 4-cylinder AWD 5-speed (Nissan)

http://www.auto123.com/ArtImages/100...-trail-i01.jpg

I loaned him my ScanGauge and set the engine size. We were really impressed with the early numbers he was getting, but became progressively more skeptical as the gas gauge approached E.

The first tank was off by a whopping amount:

Indicated: 6.7 L/100 km = 35 mpg US
Actual: 11.2 L/100 km = 21 mpg US Correction: 9.6 L/100 km = 25 mpg US

That's a huge error. 40% 29% !

Anyone else seen a gauge off by that much?

I'm sure I set the engine size. Have to double check of course. Hopefully that's all that's wrong.

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FYI, the "updated" NRCAN (post-2008 EPA similar) ratings for the Nissan are:

• city: 12.2 = 19 mpg
• highway: 9.5 = 25 mpg

He's still doing better than the Ridgeline, which was rated:

• City: 15 mpg (US)
• Highway: 20 mpg (US)

But not as well as we thought!

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Update: it wasn't quite as bad as we first thought: the gas receipt was 51.3L for 537 km (he guessed the volume when he told me, earlier). That's 9.55 L/100 km = 24.6 mpg US.

That's still a 29% error though.

The wife regularly averaged 27-28 in her Rogue. On a road trip I managed to hit close to 33 with some atrocious weather (raining cats and dogs for a couple of hours). I think I got close to 473 miles out of that tank, the light came on just before we got home with less than two gallons left on the refill.

regards
Mech

Wow, quite the difference in MPG ratings:

Rogue: 22 city / 27 hwy for the automatic 2013 AWD 4 cyl, 2.5 L

Yeah, she drove my CVT insight for a week and averaged 56 MPG. Accelerate at about 1800-2000 RPM and let it get in top gear early, about 40 MPH. The torque converter locks up by the time you clear an intersection, more like a clutch than a converter. I didn't coast in neutral in her Rogue, it was brand new and I didn't want to give Nissan any excuse to deny a warranty claim. I think the CVT is warrantied for 10 years and 120k miles. Only mode was to air up the tires.

regards
Mech

My TSX UG is off by 10% by default. I had to adjust the "gallons used" to calibrate fuel consumption.

The UG in the Camry seems spot on without any calibration.

Our 2011 LTZ Cruze with 6A-transmission (first year production) was consistently 5-7% optimistic. Later models, especially with 6M-transmissions, were often better, only 1-2% optimistic, with 6A-models 2-5% optimistic.

8% in the Odyssey 3.5 V6 5AT.
16% in my Fit with heavy EOC P&G driving. My old Civic was similar.

Still not seeing any stories of a 40% error in "normal" use.

However, it turns out my brother was "estimating" how much fuel he put in his Xtrail. Doh. (He's not fuel economy focussed.) He did get the receipt though, so I can check it later today and do proper calcs. And ensure the right engine size was used in the SG.

40% is HUGE!! SCII was 17% generous on my 05 Corolla & I thought that was a lot.

My scan guage turns off when I try EOC. :(. So I really don't know much better my mileage is if I tried EOC.

My SG reports 9999mpg when I am in DFCO and actually getting [infinity]mpg. That is by far the largest error I've seen. :p

IIRC the SG in the Fit was optimistic but no more than 10%. I played with adjusting it and drove myself nuts for a while. Finally decided to set it, forget it, and use it as a relative measure.

wdb: funny. I LOL'd.

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Do you have your fuel type set to "Hybrid"? That's what you need to do for EOC (it doesn't mean your car's a hybrid, only that the gauge should stay active while the engine is off but the key is still ON.

I double-checked the gauge settings: engine size was correct.

With the accurate numbers from his gas receipt, I entered a +30% offset for fuel use (not 40% as previously mentioned, but still waaaay off). We'll see next week if that works.

Update: after several tanks, the fuel offset is set at 41.1%

I've never seen one that far off. Crazy.

For some reason my ELM327 bluetooth scanner keeps identifying my parents Focuscape 2.0 EB as a 1.6L engine. Throws the figures off a bit.

When I changed the headers on my Subaru, my offset jumped to +15% from +7%. This I later found out was because the car was running richer than before. Scangauge II does not take AFR into equation, it always assumes a 14.7:1 AFR and i think ~12:1 for open loop.
Apps like torque pro have the ability to take AFR into consideration but they are not very accurate from my experience. SG2 is so far the most reliable and practical device I have used.

...assumed stoichiometric 14.7:1 AFR is *why* almost ALL mpg meters are seldom 100% accurate...especially, coupled with those times (short trips, cold weather, wot) when the engine is running in "open-loop" rather than "closed-loop" operation.

Yessir.

But 41% off? That should win some kind of prize!

Actually, I think I'll contact Linear Logic and ask them about it. Will post back.

Linear Logic says not only is it normal, but the developer's own car has a 30% offset:

What all do you calibrate on the SGII?

On an Ultragauge, it needs engine size, and you calibrate distance and fuel consumption. If I have it set for one car that is on one end of the ranges and move it to a car that would be on the opposite end of each range I could see it maybe being that far off, even if I change the engine displacement.

Same setup options.

I never used my sg2 for mpg, but for the other gauges. I think the 9999 is what made me assume it would not be accurate in the very first usage.

My gen 2 insight is always 2-3 mpg higher rather in sport, eco or using a mix of ethanol and regular fuel. :eek:

This has probably been mentioned before, but when MPG goes to 9999, SG still knows you're burning 0 and travelling X miles, which are the numbers used in it's calculations. It's a quirk of the display, not the underlying logic.

If you set it to metric, DFCO will simply show '0.00'. MPG is of course a non-sensical measure anyway.

Even my car's on board trip computer is off by about 4-5% everytime. No device can measure MPG accurately. However I love how my scangauge is now accurate to +/- 1% after several calibrations. I just love this piece of hardware.
9999 MPG is normal, that means fuel cutoff. You have to set your fuel cutoff settings up first. It should be approximately 4 points above your TPS value at idle.

Does the X-Trail have a throttle plate?

My plateless petrol Fiat is out by a 30% as well, and my TDi changes wildly over each tank from 8%-30% despite being driven in much the same way over much the same roads.

I wonder if changing the engine size parameter rather than cailbration yields more accurate results? On the 2.5TDi I seem to get more accurate readings if I enter 2.0 as the engine capacity and then only add a 1-2% of calibration. Thoughts?

Good question - I'm not sure if it has a plate or not. Will have to research...

How is the Rogue in regards to performance and hauling? I had a Nissan dealer willing to sell me one starting at 17 grand for last years model with 40k miles on it. Looking online it seems many of them have engine problems before approaching 50k miles. That and when the sales person clicked the dash for sport mode it didnt seem to be more sporty, but you could hear the boost from the tubo. Thinking maybe it didnt have 93 octane in the system as I know many gas stations only sell 91 and some still use 87 as they are cheap. :eek:

Looked like a rounded SUV like and I am afraid the roundness may make it too difficult to haul too much inside like how the gen 2 insight is.

When I am in town, doing lots of EOC and P&G with my Civic, the SG is 25% out, and when I go on a road trip and drive it HARD, it is out by 14%. Goes to show how much of an estimate the OBDII gauges really are.

My Insight has been as much as 6mpg off on a real mpg of 64. Last tank it was only 2.5.

I'm trying different brands of fuels to see if that makes any difference.

There's a pretty easy fix for this, for the ScanGauge.

Go into the settings, what you need is in the "Fuel" or "Fuel Type" section. Select "Hybrid". That solves the problem.

^^^What he said^^^
And also set the power down mode to "COM" instead of "KEY" or RPM".
This setup works great on the Civic. Combined with the kill switch, it's awesome. I can EOC for miles (vehicle speed keeps reading when you shut off with a kill switch as opposed to the momentary loss with a keyswitch), wait at a light for 5 minutes, and the SG is counting the whole time, not shutting off.

So, I had something interesting happen with my Scangauge yesterday. I had just pulled onto the freeway at the start of a 500-mile trip, looked down, and noticed that my average for the trip so far was reported at 106mpg! Then I looked at the instant mpg: the Scangauge was reading 9999 under throttle, and continued to do so for several miles, until I pulled the cord and let it reset. Anyone else had this happen?