The unorthodox plan to spend quattro months each in three variants of the Audi A3 Premium Plus sedan proved its merit. Starting in a front-wheel-drive 2015 A3 1.8T, moving to a 2015 A3 TDI, and finishing off with an all-wheel-drive 2016 S3 showed us all facets of the compact, luxury, all-wheel-drive sedan: the good, the not so good, and the very best. We traveled a combined total of 20,696 miles in a year and lost only a few days due to unforeseen visits to the dealership's service department.

Aside from powertrains, all three were essentially equipped the same: Premium Plus trim, metallic paint, and MMI Navigation Plus. This trim affords upgraded wheels/tires, heated power front seats and side mirrors, keyless entry/ignition, and aluminum trim inside and out. Audi's MMI Navigation Plus package with voice control (dubbed the Technology package in the 2016 S3 with blind-spot monitors added) includes crisp graphics operated with a nifty touchpad/twist knob controller.

2015 A3 1.8T

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Our first A3 arrived with a peppy 170-hp turbo-four and about 8,000 miles on its odometer. But its track-tested 7.1-second dash to 60 mph isn't much better than a base Honda Accord four-cylinder. Real MPG mileage, however, was 6 to 8 percent better than the EPA-rated mpg estimates of 23/33/27 city/highway/combined. The car's compact dimensions made it a natural for the urban cut-and-thrust of commuting—so did an engine that's biased toward torque (200 lb-ft at 1,600 rpm), a quick-shifting six-speed dual-clutch automatic transmission, and responsive steering.

We were impressed with the simplicity and intuitive operation of Audi's top-shelf MMI infotainment system. The convenience of onboard Wi-Fi, the wow factor of a Google maps option within the navigation system, and the wealth of information available through Audi Connect data services proved its worth over and over. The A3's attractive interior and soft leather seats also drew high praise (and gratitude for the three-stage heating), but the A3's back seats don't accommodate full-sized adults in the lap of luxury. Front seat backs are bulky, the roofline makes ingress/egress challenging, and so on. Also, taller drivers might find the rotated sunvisor not long enough to block out the sun peering in from the side window.

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Just as we were easing into this relationship and approaching the 15,000-mile mark, the unknown unknowns began popping up. The tire pressure monitoring system erroneously alerted us to low pressures. An intermittent check engine light came and went. A faulty rear window regulator caused a loud click at the end of the window's journey upward. Finally, undue engine oil consumption and a pinhole-size leak in a coolant-system fitting quickly made us think that Audi's poor reputation for reliability might have some teeth. With the exception of the engine oil needing to be topped off periodically (apparently "they all do that"), all of these worries were fixed to our satisfaction, free of charge within the warranty. What we weren't expecting was an invoice of about $400 from the dealer for the 15,000-mile scheduled service visit, which mostly consisted of an oil, oil filter, and cabin air filter change.

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2015 A3 TDI

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All the qualities that were part of the A3 1.8T repertoire also applied to the TDI. What was missing, however, was the quiet, sophisticated ride and engine/transmission response. In lieu of an expensive multilink rear suspension, the TDI instead rides on an anvil-simple torsion-beam rear axle. And lacking shift paddles, the only time the A3 TDI felt like it was in sync with the commuter's urgent desires was when the transmission's shifter was in Sport mode or notched over in the manual-shift gate.

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At the test track, our 150-hp TDI with 7,500 pre-arrival miles on the clock was no slouch, running to 60 mph in a not-dreadful 8.2 seconds and rounding our figure-eight course 0.1 second ahead of the 1.8T with its 26.6-second lap. With tires that had more rubber-to-road contact, it stopped shorter from 60 mph, too (108 feet versus 112) . Where the TDI really shined was, of course, fuel economy. We did not manage to gather Real MPG data on the car prior to its departure, and considering the worldwide diesel controversy that erupted at the time, we missed a golden opportunity. We did, however, log more than 7,500 trouble-free miles on the car prior to its departure and averaged 37.5 mpg over that four-month period, beating the EPA's combined estimate of 36 mpg.

2016 Audi S3

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As if all the rings in the Audi badge aligned perfectly, the all-wheel-drive 2016 Audi S3 arrived with just 800 miles on its odometer. The (special wheels with summer tires and self-adjusting magnetorheological shocks), and some of the most handsome diamond-quilted sport seats you'll find made this A3 derivative feel like a completely different car. It blazed a 4.4-second 0-60 time and lapped the figure eight in 25 seconds flat. That first figure, incidentally, beats the last Mustang GT we tested, and the S3 nearly matches it in the second.

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In terms of everyday driving, we found the S3 an absolute mind reader. With the Drive Select mode in Automatic and the transmission in Drive, the S3 was smooth and docile with predictable acceleration and intuitive automatic gear changes. The Real MPG lab returned slightly less efficient results than the EPA's 23/31/26 mpg city/highway/combined with 20.3/32.0/24.3 mpg. Over the first portion of the four months, we averaged an observed 24.4 mpg, which fell to 23.3 and finally to a disappointing 21.9 mpg in mixed driving. We also needed to add a $9.80 quart of oil. We probably can take the blame for the plummeting fuel economy, but that extra oil consumption seems to be a pattern here.

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Our stroll then saunter then hot lap through the Audi A3-S3 line was a treat not many people can claim to have had. We generally enjoyed our time with the affordable A3 1.8T, but only when it was behaving as a new car should. Audi has some clear problems with oil consumption (demonstrated by both gasoline-powered engines needing periodic replenishment) and build quality (as evidenced by the 1.8T's laundry list of glitches and fixes). We loved the fuel economy of the TDI but didn't care for how it actually drove. In the end, the pocket-rocket S3 redeemed the model with breathtaking performance at the cost of sub-optimal fuel economy. We wish we could combine them into one Audi compact luxury sedan that does it all, reliably and for a reasonable price, but that's not going to happen.

Among the three we drove, there's an A3 (or S3) for everyone. Enthusiasts that we are, it has to be the S3.

More on our long-term Audi A3 and S3 here:

Our Cars 2015 Audi A3 1.8T (Premium Plus) 2015 Audi A3 TDI (Premium Plus) 2016 Audi S3 (Premium Plus) SERVICE LIFE 4 mo/7,419 mi 4 mo/7,553 mi 4 mo/5,724 mi BASE PRICE $30,795 $33,495 $43,425 OPTIONS MMI Navigation Plus ($2,600: Navi w/voice control, MMI touchpad, CD/DVD player, HD radio, Audi Connect), Premium Plus ($2,550: 18" wheels, heated/power front seats, heated mirrors, keyless entry/ignition, aluminum interior/exterior trim); metallic paint ($550); chrome exhaust tips ($150) MMI Navigation Plus ($2,600: Navi w/voice control, MMI touchpad, CD/DVD player, HD radio, Audi Connect), Premium Plus ($2,550: 18" wheels, heated/power front seats, heated mirrors, keyless entry/ignition, aluminum interior/exterior trim); metallic paint ($550) Technology ($2,600: Navi w/voice control, MMI touchpad, CD/DVD player, HD radio, Audi Connect, side assist), 19" Performance ($1,500: 19" wheels/summer tires, magnetorheological shocks); S Sport Seats ($1,450); metallic paint ($575); Red brake calipers ($400) PRICE AS TESTED $36,645 $39,195 $49,950 AVG ECON/CO2 24.7 mpg / 0.79 lb/mi 37.5 mpg / 0.59 lb/mi 21.9 mpg / 0.89 lb/mi PROBLEM AREAS Check engine light, TPMS alerts, door rattle None None MAINTENANCE COST $410 $0 $0 NORMAL-WEAR COST $0 $0 $0 3-YEAR RESIDUAL VALUE* $17,223 $21,165 $27,972 RECALLS None None None REAL MPG CITY/HWY/COMB 24.4/35.6/28.5 mpg Not Tested 20.3/32.0/24.3 mpg *Automotive Lease Guide data

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