A sports car is proof that it certainly is more fun in owning something you don't need than having to buy something you really need. But, then, luxury has always been more interesting than necessity.

Today's test car, the Nissan 300ZX Turbo, like other sports cars, is an expression. And depending on where you are coming from, the expression may be slightly different. Whether you happen to be a yuppie, a driving enthusiast, a real sport or a mid-life crisis candidate, a 300ZX Turbo will surely make life more interesting. If you have an ego that needs stroking, you surely should give this car a closer look.

The 300ZX is not only incredibly fast, incredibly maneuverable and incredibly good-looking, it is also incredibly luxurious and comfortable. At this point, though, I should add that it is also somewhat incredibly priced, but we will get to this later.

The latest member of the Datsun/Nissan ''Z'' series sports cars that began back in 1970 with the Datsun 240Z, the 300ZX Turbo is living proof that just about everything improves with age - to a certain point, of course. This model was only introduced two years ago but Nissan has restyled it for the 1986 model year to give it a wider and more aggressive look. One thing about Nissan is that it doesn't let well enough alone. This Japanese automaker is noted for changes and perhaps this is the reason the 300ZX is the best selling sports car in America.

Anyway, the wider look was achieved by flaring the front and rear fenders out about two inches to increase the track and, on the turbo model, making room for wider tires. Track width has been increased about an inch-and-a-half and the turbo model now uses 16-inch 225/60 V-rated tires. Styling changes also include the use of flared rocker panels, a front air dam and a rear spoiler and bumpers that are colored keyed to match the paint on the car.

The suspension on the turbo model has been re-tuned for improved cornering and steering response. And somewhat interestingly, underhood ventilation has been improved, permitting the elimination of the hood air scoop for a smooth hood line. Inside the car, the bucket seats have been lowered about an inch and the steering wheel has been redesigned for improved feel and driving control. A three-position power lumbar support has been added to the driver's seat as standard equipment. The high-mount stop lamp, a safety feature on all 1986 cars, has been integrated into the rear spoiler.

All-in-all, the 300ZX looks even more sportier than last year's model which itself was a handsome car.

The 300ZX has a wheelbase of 91.3 inches, overall length of 170.7 inches, width of 67.9 inches, height of 51 inches and curb weight of 3,267 pounds. It is one of the largest sports cars around these days and much of its size is apparent in the interior, which is almost sinfully roomy. There is not only room for driver and passenger to stretch out, they can also reach out and swing out. Storage room behind the seats is excellent. A lot of luggage and a lot of sporting equipment can be fitted in.

The test car had the optional electronics/electric package which even made the interior more impressive looking. If you like video games and home computers, you'll probably love the electronic instrument panel. It features the usual digital readout speedometer and bar graph instruments but for a bit of added attraction also has a tachometer that is a combination of analog and digital display. Of particular interest, is that the analog display has a two- dimensional graph that shows where the engine is on the power curve. This is strictly for the serious driver.

The 300ZX is not the type of car that anyone can jump into and drive (nor should they be allowed to). Steering is quick and responsive and does require some concentration. The car turns quickly, where it is steered, whether or not the dr ver had that intention. In other words, you can't day dream and just move the steering wheel back and forth. The 300ZX Turbo is made for the serious driver and it is just about as good as you can get when it comes to handling. If you have the urge and the ability, you can make it do tricks. Even average drivers will look a little better in this car.

The four-wheel independent suspension features MacPherson struts all around and a three-way adjustable shock absorber system that allows the driver to select firm, normal or soft settings at fingertip reach while the car is in motion. The firm setting, of course, will provide the best handling. The ride, as should be expected, is somewhat firm but acceptable, especially to those used to sports cars. The normal setting is a little softer and the soft setting just a little too soft.

I must admit, though, that I did use the soft setting on cement interstate highways to try to soften up slab bump (you know, the thump you hear and feel on the cracks between the slabs). It seemed to work well but then when negotiating a curve, without changing the setting, things got a little touchy. I decided to leave it in firm and forget it. What might help the three-way shock system would be an indicator light on the dash to inform the driver of the setting. (After all, it has every other kind of indicator.)

But, no doubt, the most impressive feature of the 300ZX Turbo is its engine - a turbocharged fuel-injected three-liter/180-cubic-inch V-6 rated at 200 horsepower at 5,200 rpm and 227 foot pounds torque at 3,600 rpms. Just press that designer shoe on the accelerator and you are on your way. Turbo lag is very slight and can be easily overcome by anticipation and keeping up the engine revs. But even so, the engine is forgiving. You can let it drop rpm and it will pick up reasonably quickly. The engine is pleasantly noisy but you really won't notice it unless you open the windows and/or take out the roof panels.

The test car had a five-speed manual transmission (a four-speed automatic is available) that operated as smoothly as the engine. The engine/transmission combination will provide surprisingly good fuel mileage. The 300ZX is by no means an economy car, but for a car with 200 horses the mileage isn't bad at all. The test car averaged 16 miles per gallon for city driving and 24 mpg over the highway. Premium unleaded must be used because of the turbocharger.

Base price for the 300ZX Turbo is $21,099. The base includes all kinds of power equipment and what would normally be considered options. Name it, it has it. In fact, the only option on the very well equipped test car was the electronics/leather package at $2,350. Add to this a delivery of $210 and the final line is $23,659. This would certainly be a tidy sum for a necessity but not really bad for a luxury. The non-turbo Z line begins at $18,099.