Mileage Challenge 5.4: The Results

Mileage4
Our latest mileage challenge had editors logging more than 300 miles each in three hybrids and a diesel: the 2010 Honda Insight, 2010 Mercury Milan Hybrid, 2010 Toyota Prius and 2009 Volkswagen Jetta TDI. We tallied up all the numbers and corrected for a brief photography stint between Legs 2 and 3. (Angling cars around for the camera — complete with rapid stops, starts and idling — has a way of dinging your mileage, and it’s not representative of real-world driving.)

The results were striking.
MileageData_10.09

In stark contrast to MotorWeek’s observed numbers — they got 36.2 mpg in a stick-shift tester — our Jetta TDI reported a most impressive 47.0 mpg in trip-computer mileage. That’s far better than even the car’s 40-mpg highway rating, and we didn’t drive any differently than we normally do.

Then came the fill-up. We thought there might be something wrong with the TDI’s pump when it clicked off at 5.60 gallons. After all, the Insight had taken 6.31 gallons, and its trip computer reported 53.7 mpg. Data editor Matt Raskin clicked the diesel pump off twice. No dice — the TDI was full.

The pump calculations worked out to an even more astonishing 56.5 mpg – just 1 mpg short of the 50-mpg-rated Prius, and nearly 10 mpg better than the TDI’s trip computer reported.

Why the wide discrepancy? In past mileage challenges we’ve considered the reasons trip computers don’t always compare with at-the-pump calculations. Experts have cited a number of factors that can skew the amount of gas a pump doles out, but they generally agree that when you’re only filling up with a few gallons — as we ended up doing — trip-computer readouts are a more reliable assessment of gas mileage.

Mileage41
Either way, it’s safe to say our foursome proved thrifty beyond expectation. Our route netted an average 44 mph — a speed that favors most cars’ highway ratings. Compare our results to those ratings, and the Prius was thriftiest overall. Observed mileage came in 31 percent better than the car’s 48-mpg EPA highway figure. In respective order, the Insight, Milan Hybrid and Jetta TDI fared 25 percent, 23 percent and 18 percent better than the government’s highway mileage rating.

Compare the results against combined EPA city/highway ratings, and the Jetta TDI runs away with it. Our observed mileage was 42 percent better than the car’s 33-mpg combined rating. In descending order, the Insight, Prius and Milan Hybrid follow.

Go figure — and go VW. We’ve heard of similar outsized results from TDI owners, but now we have some of our own. Color us impressed.

Route Notes

Leg 1: 69˚ F, partly cloudy
Traffic: Medium (5/10)
Heading: NNW, no wind
Average distance: 83 miles
Average speed: 32.25 mph

Leg 2: 70˚ F, partly cloudy
Traffic: Light (2/10)
Heading: NNW, 4 mph tailwind (from S)
Average distance: 71.5 miles
Average speed: 58.75 mph

Leg 3: 70˚ F, partly cloudy
Traffic: Light (2/10)
Heading: SSE, no wind
Average distance: 74.5 miles
Average speed: 56.5 mph

Leg 4: 73˚ F, partly cloudy
Traffic: Medium (5/10)
Heading: SSE, 3 mph crosswind (from ENE)
Average distance: 84 miles
Average speed: 43.75 mph

Previously
Mileage Challenge 5.3: Dizzying Displays
Mileage Challenger 5.2: Avenues and Interstates
Mileage Drive 5.1: Hybrids vs. Diesel

Comments 

Zack

Congratulations to Toyota for claiming the top MPG figures, and to the also-rans for their respectable performance. Just think of how much oil we wouldn't be importing if everyone drove one of these vehicles.

Ziggy

Wow! I'm impressed with all 4 of them, especially the Prius numbers. "May the best car win" ...oh wait, wrong manufacturer.

Phil

It seems hard to calculate Prius pump fill-up since the fuel bladder (tank) drastically expands and contracts, meaning you can fit in more or less gas at the pump. Was this accounted for?

Wow...I thought that the Jetta nearing 50 MPG was pushing it!

It's great that all of the cars got above their ratings, great numbers for all 4 of them.

JM

Take that Hybrit.

Mark

The prius is the width of a walmart shopping cart. Hardly equal to the other three.

Next time include 49cc mopeds in the mix if you're going to make such uneven comparisons.

John

I've got a VW diesel, and it does get great mileage. But the reported fill mileage is not accurate, because diesel fuel has a lot of foam when you fill it. You have to wait several minutes to let the foam settle before you top it off. I would be very surprised if it truly was better than the 47 mpg on the computer.

Anel

"The prius is the width of a walmart shopping cart. Hardly equal to the other three."

What? The Prius is wider than the Insight and within 1.5 inches of the Jetta. Where are you getting your figures?

Tony

I wouldn't jump into hybrid band wagon just yet. Cause, as we all know, the battery performance will suffer in the cold climate. So, after all, the EPA may be right. Including winter/summer change, the average mileage will be closer to EPA numbers.

In that light, the Jetta looks strong as its mileage shouldn't suffer a lot from the climate change. But diesel is more expensive.

Another dark side of hybrid cars is the pollution they bring in the process of making them.

Each coin has to sides. We can't just jump into any conclusion.

Zack

Guys, I'm going to have to agree with John. The TDI is a nice car, but I doubt it delivered the real world mileage reported here. There's a reason that the EPA is the EPA and I'm going to trust their numbers, not the ones reported here.

I actually own an '09 Jetta TDI. I also keep a log book in the car and can account for each tank of fuel since I bought the car new in late April. I drive A LOT. I frequently get over 50 mpg on the highway, but that's driving conservatively (65 mph instead of 70, etc.) My average mpg PER TANK is about 45. That's after 18K.

Real world mileage is just that, not a magazine article or EPA. And it varies, sometime by a great degree, for each driver. I'd drive any of these cars over a regular vehicle. And I'd probably getter better mpg than the regular person because of my driving habits, even though I'm not a nutty hypermiler, just riding the diesel "torque curve" and using common sense, unlike many of the people around me each day. I'm getting tired of all these shoot outs between alternative cars. I'm not sure how useful they are to someone wanting to buy a new vehicle. I can only speak for the TDI. It's a great car, really fun to drive. If you just get in and drive like an idiot, I'm not sure what you're fuel economy will be. If you learn how to drive it, you will probably get between 40 - 45 mpg average, because of the more powerful engine in the '09 and all the clean diesel mods. This is hand calculated, but the display is pretty accurate in the car. Some folks get less, some more than this (check out the TDIclub forum.) Diesels need to warm up, break in, and be driven a little differently. The EPA is not real world. But you're not going to average 56 mpg, either, except maybe in an older, less clean model from before '06.

Hybrit

The Jetta TDI is not even on the government's top ten list of the most fuel efficient cars. I salute the TDI owners- JBright and John- for telling us the truth - that there's no way a Jetta TDI can match a hybrids economy.

KWV

Hybrit, you're just being obtuse. I have a 2006 Jetta TDI, and I regularly get better real world mileage than my friend does in his 2008 Prius. Check the data at fuelly.com, and you'll see that VW diesels beat most hybrids and compete handily with the Prius.

Whoa, Hybrit, hold on there pardner...the truth I was trying to reveal was that the TDI is every bit the equal of a hybrid, one more option for the American public. 45 versus 50 is not that much fuel, and the TDI has definite advantages that appeal to a certain segment of the driving population who might not go for a hybrid. Why do we have only one diesel option, when in Europe (not known for its anti environmental stance or stupidity) the majority of cars are diesel? And, sorry, the pre 2009 TDIs do match the Prius in fuel ecoonomy. Heck, when I hypermile in my '09, with its substantially more powerful common rail engine, I can get 65 mpg, too, but how relevant is that to the common car owner? And I doubt some of the mileage claims the Prius fans make anyway. I've read your forums and know there are people who aren't getting that magic 50, as well as people who wonder if Toyota cooks it's dashboard display data. Inflatable, variable fuel bladders? How do you accurately calculate your tank average so confidently then? Mine's easy. I have absolutely nothing against hybrids. I almost bought one, but liked the TDI better (and I'm an extremely informed customer.) In Europe now, there are diesels with stop/start and regenerative braking. And they get incredible fuel economy. I love my Jetta. I got 51 mpg coming home from Whole Foods tonight on the freeway. I want more hybrids and more diesels and more electric cars, not more guzzlers that can't begin to match what most cars got in the 1980s.

JohnQPublic

Those who think the Prius is "small" need to look at the interior volume numbers. The Prius actually has MORE interior space than the Jetta.

Also, the Jetta TDI tested is a manual. You can't really compare that to a Prius, which is a PRND car. It's fairer to compare the Prius to an automatic Jetta (DSG gearbox).

I doubt the DSG Jetta TDI can get mileage anywhere near as good as the manual, since you can't do things like rev-matching with an automatic.

john q public,
if you had read post 1 you'd see the TDI Jetta was the DSG auto not the manual. Thanks!

The DSG gives up a single mpg highway according to the EPA rating for the '09. For the 2010, it's actually rated 1 mpg higher. Diesel torque is all low end and mid range (below 2500 rpm) and, in my experience with the DSG, the computer can shift faster and more efficiently than I can. What's up with negativity toward diesels? Have you guys ever driven a TDI?

We studied the indicated versus actual error of the 2010 Prius (ZVW30) and found a 5% error on the high side. So your indicated 63.1 MPG would correct to 59.9 MPG.

The ZVW30 no longer has a bladder tank.

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