The Mosler Twinstar Was a Dual-Engine, 575-HP ’90s Super Cadillac

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Collapsing in 2013 due to the lack of sales, Mosler Automotive joined the ranks of many a defunct supercar manufacturer. Before it departed, however, it left us with more than a few cars to remember it by, such as the ugly-but fast Consulier GTP that was banned from IMSA, and the supercar-fighting MT900. But then there is the 1999 Twinstar; a heavily-modified Cadillac Eldorado powered by—as its name implies—two Northstar V8 engines.
The Twinstar’s origins reportedly lie in a misunderstanding between company founder Warren Mosler and one of his golfing pals, whom he had brought by the shop to show off a mockup of an upcoming, mid-engined performance car called the HP40 (short for high performance, 40 mpg). According to a Street Muscle interview with a former Mosler engineer, Mosler’s guest proclaimed something along the lines of “wow, cool, a twin-engined car,” an idea Mosler liked so much that he turned the HP40 into the Twinstar.
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Mosler’s Twinstar brochure
Twinstars’ dual powertrains operated almost entirely independent of one another, with separate ignition circuits, ECUs, and individual four-speed automatic transmissions—no center differential or transfer case. The two powertrains were also apparently not of identical specification; the rear engine was slightly more powerful and had a higher redline, but shorter gearing, meaning the engines almost never shifted in tandem according to a 2000 Car and Driver test.
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Mosler Twinstar’s rear engine
What the two Northstars did share was a single accelerator that opened the throttle on 9.1 liters of octuple-cam American fury, specifically 575 horsepower and 595 pound-feet of torque. Despite weighing in at 4,780 pounds, these could rocket the Twinstar from zero to 60 in as little as a claimed 4.6 seconds, down the quarter-mile in 12.7,  and to a limited top speed of 126 mph. The bulk and thirst of a second engine reportedly gave the Twinstar a pathetic 10 mpg, though it apparently didn’t hurt handling. Reportedly, the Twinstar recorded 0.83 lateral G on a skidpad—on par with a current Porsche Cayenne Turbo (as tested by Motortrend).
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Because Mosler lengthened the rear end, the Twinstar still had back seats, which were as luxurious a place to sit as 1990s General Motors could imagine. It had a leather interior, a CD-compatible stereo, air conditioning, and power everything. What all this cost is the subject of dispute; the brochure above (circa 1998) touts a starting price as low as $64,500 in today’s money, though Car and Driver reported the conversion could run over $108,000 today.
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Mosler Twinstar
Such price tag, in conjunction with the Twinstar’s strange styling and a doubled risk of popping a head gasket, is likely what resulted in its atrocious sales. Only five were ever sold, three reportedly to a single ultra-wealthy kook who wanted to keep driving with a radiator shot out, and one to Jay Leno according to RM Sotheby’s. Such rarity makes their value today hard to gauge, though sales in the mid-late Twenteens suggest sale prices in the mid-to-upper five figures are typical. For what’s probably the last 16-cylinder Cadillac, maybe those prices aren’t too batty.
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Or a friend who would let us drive a Mosler Twinstar?
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