2015 Kia K900 V-8 Long-Term Update 3
You'll Notice a Difference Above 90 mph
When your daily driver makes more than 400 hp, it's tough to notice an extra 10 horsepower here and there. My 2015 Kia K900 V-8 long-termer produces 420 hp from a 5.0-liter V-8, but the owner's manual also allows for the use of 87-octane fuel, noting that 91-octane will simply result in "improved vehicle performance." Makes sense, but just how big of a performance difference could there be? Since Motor Trend actually tests many fleet vehicles, the K900 V-8 was evaluated at the track first on the recommended (but not required) 91 and then on 87. Here's what we found.
Subjectively, I can't say I have ever noticed a significant change in the 2015 K900 V-8's performance or sound from behind the wheel on the two types of fuel. The nose jumps a little at wide-open throttle in both cases, and, since the car is so quiet, the V-8's engine sound is suitably muted either way. Kia might not provide different horsepower or torque ratings on 87 and 91 for the 5.0-liter V-8, but Hyundai does for the 2015 Equus. That K900 platform-mate uses a version of the V-8 that produces 429 hp at 6,400 rpm and 376 lb-ft of torque at 5,000 rpm to the K900 V-8's 420 hp at 6,400 rpm and 376 lb-ft at 5,000 rpm. The 2015 Equus, Hyundai says, loses 8 hp and 11 lb-ft in the transition from premium to regular fuel. While the Equus and K900 V-8 don't share perfectly identical specifications, they're close enough to give us an idea of how much the Kia sacrifices when its owner goes for the cheap gas.
On the track, our K900 V-8 completed the 0-60 mph sprint in 5.6 seconds while testing on 87 as well as on 91. In fact, the two test results from 0-70 mph and 0-80 mph (7.2 and 8.9 seconds, respectively) were also identical. It's only with the 0-90 mph times that the 91-filled K900 V-8 puts some distance on the same car tested on 87 -- an entire tenth of a second, so nothing especially significant. From 0-100 mph, the 91 car's 13.3 seconds is a bit better than the 87 car's 13.5 seconds. The quarter-mile times were both 14.0 seconds, but at 102.3 mph for the 91 car and 102.1 mph for the 87 car. What we can't tell with our test car is what long-term effect -- if any -- regularly using 87 instead of 91 could have on the K900 V-8's engine.
These incredibly close track-tested results suggest that the K900 V-8, like the related eight-cylinder-standard Equus, isn't losing much power stepping down from 91 to 87. And that's great, but a minor problem pops up when you compare the K900 V-8's performance against better-established and more expensive competitors. With the Kia's 5.6-second 0-60 mph time in mind, let's start with a comparison-test-winning 2011 BMW 740i powered by a turbocharged I-6 that car got to 60 mph in 5.5 seconds. True, the BMW wasn't a long-wheelbase model, but it's striking that a 315-hp car keeps up with the 400-plus-hp K900 V-8 in a sprint yet also gets an EPA-rated 19/29 mpg to the Kia's 15/23 mpg. We also tested a long-wheelbase 2013 Audi A8 with a 333-hp supercharged V-6 that reached 60 mph in 5.3 seconds. (A 2015 A8 L with that engine is EPA-rated at 19/29 mpg.) The K900 V-8 and a 2013 Lexus LS 460 F Sport are better matched, with the 386-hp, eight-cylinder Lexus reaching the 60-mph finish line in 5.6 seconds just like the Kia, with EPA mileage of 16/24 mpg.
Make no mistake, the privilege of simultaneously getting better performance and fuel economy doesn't come cheap. While the Kia is loaded at $66,400, good luck finding a reasonably equipped A8 or 740i under $80,000. The Lexus is slightly cheaper than the BMW and Audi, but still thousands more than the Kia. The K900's V-8 will probably serve as a fine upgrade over the K900 V-6 (the six-cylinder models arrive at a later date), but if anyone weirdly fantasizes about drag-racing quiet luxury-focused sedans, there are quicker and more efficient options -- if you're willing to pay the price.
More on our long-term Kia K900 V-8 here:
|2015 Kia K900 (91 octane)||2015 Kia K900 (87 octane)|
|PRICE AS TESTED||$66,400||$66,400|
|VEHICLE LAYOUT||Front-engine, RWD, 5-pass, 4-door sedan||Front-engine, RWD, 5-pass, 4-door sedan|
|ENGINE||5.0L/420-hp/376-lb-ft DOHC 32-valve V-8||5.0L/420-hp/376-lb-ft DOHC 32-valve V-8|
|TRANSMISSION||8-speed automatic||8-speed automatic|
|WHEELBASE||119.9 in||119.9 in|
|LENGTH x WIDTH x HEIGHT||200.6 x 74.8 x 58.7 in||200.6 x 74.8 x 58.7 in|
|0-60 MPH||5.6 sec||5.6 sec|
|QUARTER MILE||14.0 sec @ 102.3 mph||14.0 sec @ 102.1 mph|
|BRAKING, 60-0 MPH||122 ft||-|
|LATERAL ACCELERATION||0.80 g (avg)||0.79 g (avg)|
|MT FIGURE EIGHT||27.5 sec @ 0.64 g (avg)||27.6 sec @ 0.63 g (avg)|
|EPA CITY/HWY/COMB FUEL ECON||15/23/ mpg||15/23/ mpg|
|ENERGY CONS., CITY/HWY||225/147 kW-hrs/100 miles||225/147 kW-hrs/100 miles|
|CO2 EMISSIONS||1.09 lb/mile||1.09 lb/mile|