Does the Volkswagen Jetta 1.4T Render the Diesel Engine Pointless?

Fuel economy-minded buyers have long been drawn to Volkswagen's TDI diesel-powered cars. But in September, the Environmental Protection Agency called out the automaker for cheating on emissions testing with some of its diesel vehicles. VW then had to put a hold on selling new diesels, leaving car buyers searching for an alternative.

But Volkswagen already has another option available—the gasoline-powered, 1.4-liter turbocharged four-cylinder Jetta.

We recently bought a new 2016 1.4T SE Jetta (which showed a lot of potential in our first drive in October), and tested it extensively at our track. When we compare the results of the 1.4T to those of the diesel-powered 2015 Jetta TDI we've previously tested, we started to question the value of diesels in passenger cars, in general.

One thing to remember: Fuel economy and acceleration results for the 2015 Jetta TDI that we tested could change after VW fixes the emissions issue. After all, when we put a VW diesel in what we believe is the “cheat mode” used to pass emissions testing, we found that fuel economy fell.

Consumer Reports has suspended recommendations on applicable Audi and Volkswagen models until they are updated and their performance verified.

Let's break down how the new 1.4T Jetta stacks up against its TDI sibling.

Fuel Economy

Diesel still holds the upper hand, but the margin has diminished considerably. We measured 37 mpg overall with the diesel and 32 mpg overall with the gasoline 1.4T. Highway fuel economy, long a diesel stronghold, also goes to the TDI, posting 53 mpg. But no one should complain about the 1.4T's 47 mpg in the same test.

Fuel Costs

On nationwide average, diesel costs more than gasoline. This offsets the benefit of buying fewer gallons of fuel. Calculated based on driving 12,000 miles a year in mixed traffic conditions, the TDI will save you all of $55 a year compared to the gas-fueled version.

Emissions

The gasoline engine conclusively wins here. Gasoline-powered engines emit very little nitrogen oxide, a stumbling point for diesels and the nexus of VW's emissions cheating woes. Even though the 1.4T consumes more fuel than the diesel, typically a direct proxy for greenhouse gas emissions, combustion chemistry leaves diesels emitting approximately 15 percent more carbon dioxide per gallon consumed. According to the EPA’s test data for the 2015 model, the TDI generates 2 grams more of the greenhouse gas each year, making it basically a wash with the less-efficient 1.4T. (Should the emissions recall affect the diesel fuel economy, the emissions balance should still strongly favor the gasoline engine.)

Acceleration

The gasoline-powered 1.4T, tested with a six-speed conventional automatic, has a slight edge over the diesel TDI, tested with a six-speed dual-clutch automatic. Zero-to-60 mph sprints take 9.1 seconds for the 1.4T, making it just 0.2 seconds quicker than the diesel. The gasoline engine is also slightly quicker and faster through the quarter mile than the diesel, running the distance in 16.9 seconds compared to 17.3 seconds for the diesel.

On the Road

Typically, diesels pull strongly for highway merging and passing, and small-displacement gasoline engines feel taxed. But in the case of these two cars, neither proves true. The TDI often feels slow, especially around town. We were pleasantly surprised by the 1.4T. It seldom feels underpowered, even with several adults in the car. And, one cannot dismiss the 1.4T’s refinement edge over the diesel’s clatter.

Sticker Price

Apples to apples, there’s a $2,850 difference between the 2016 1.4T and the more expensive 2015 TDI, both equipped in SE w/Connectivity trim. (Trim line differences muddy the comparison between the sticker prices of our two test cars. Also, the 1.4T is constrained to lower-level trim lines, while the TDI was available in fully loaded versions. For now, there is no 2016 Jetta TDI.) While increased resale traditionally bumped TDI diesel values on the used market, that remains an open question now. We'd rather save the money upfront, not knowing how a future emissions recall could affect efficiency and performance.

The Bottom Line

Given the negligible difference in fuel costs, the major bump in purchase cost, and the slight sacrifice in performance, it's hard to make a case for the diesel vs. the 1.4T. Also, keep in mind that there are other super-efficient gasoline-powered cars, namely the Mazda 3 and Mazda 6, that can meet or beat the Jetta 1.4T's fuel economy. (That's not even counting hybrids, several of which are more efficient than either Jetta.) All of these options, combined with the environmental downsides of diesel, make it increasingly difficult to prove diesel's case, at least in small to midsized passenger cars.

More from Consumer Reports:
5 least reliable cars from Consumer Reports' survey
How to buy long-lasting tires
Best cars for making it to 200,000 miles

Consumer Reports has no relationship with any advertisers on this website. Copyright © 2006-2015 Consumers Union of U.S.