How accurate is trip computer for ave. MPG?

I've put around 500 miles on this 06 Jetta and it says over 54 MPG. I've driven a mix of highway and around town. Is this possible or typical? The only mod is a Rocketchip tune and the wastegate is blocked fully open.

ALL trip computer MPGs are an approximation. How accurate is yours? The ONLY way to answer that question is to calculate your MPG the old fashioned way...at each fill-up with pencil and paper/calculator.

OK but I don't expect to own it that long.

If you don't own it for more than a tank or two, then what difference does it make????

...you must be flipping it???

Yes. If I advertise it as getting 54 MPG I'd like to be sure it does.

Automatic or 5 speed manual? See my avg mileage in signature (equates to 41.4 over 335 tanks). My best ever was 52.6 US mpg and I was highway only driving 55 mph...


Here's a link to fuelly (for 2006, any body style, diesel) that shows a distribution "Based on data from 417 vehicles, 32,450 fuel-ups and 15,543,124 miles of driving, the 2006 Volkswagen Jetta gets a combined Avg MPG of 39.38 with a 0.06 MPG margin of error." http://www.fuelly.com/car/volkswagen/jetta/2006?engineconfig_id=291&bodytype_id=&submodel_id=1139

5-speed

Dangerous to advertise any MPG, unless you have proof. Again, the ONLY proof would be your own experience, with appropriate receipts.

As other's have said, we can't tell you how close your computer is. I can tell you mine was always at least 10% optimistic and usually closer to 15%.

My A5 manual, driven ~70/30 hwy/town, was usually pretty close to 44 mpg each tank. Computer would usually be up around 50. Those numbers are similar to what I have seen from others but VERY dependent on driving mix, fuel, driving style, etc.

atikovi said:

Yes. If I advertise it as getting 54 MPG I'd like to be sure it does.

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If the display says 54 MPG, then you are perfectly within your rights to tell that to any potential buyer. VW designed and manufactured that gauge, not you. Therefore, it is VW, not you, who is responsible for its accuracy and you have every right to rely on the information the gauge presents to you, subject to any limitations described in the owner's manual, if any. Furthermore, fuel mileage will vary widely based upon driving style, ambient conditions, road surface, etc., etc., which is another reason why no one can prosecute you for saying what the gauge does.

no one can prosecute you for saying what the gauge does.

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Just because it's not illegal, doesn't mean you should do it. Stating "54 mpg" in the ad implies that you've been keeping records, and 54 is your reported average. This is obviously not the case here.

People interested in TDI's are aware of the mpg advantage, and know how to look up stats on epa.gov or wherever.

This is what I did: I used the fuelly app to get accurate MPGs, then I have adjusted the reading on my car using VCDS. Now the display is off only by 1 MPG.

turbodieseldyke said:

Stating "54 mpg" in the ad implies that you've been keeping records

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No, it does not. It only implies that you have some way to back up your claim, and there is absolutely nothing wrong, let alone unethical, about saying that the vehicle's fuel economy gauge is the source of that claim.