Are left and right struts assembly interchangeable?

The front left and right are the same regardless if you replace just the struts or the complete assemblies. There's no need to replace them if you aren't having any problem.

Shock absorbers reduce a vehicle's tendency to continue bouncing up and down after hitting bumps in the road. They collapse easily to prevent a bump from forcing the vehicle up, which would be very uncomfortable, and they pull apart rather hard to prevent the tire from dropping down into a pot hole as you zoom across it.

Struts perform the same function as shock absorbers, but they are also a structural part of the suspension system that holds the wheel in alignment. With either one, the first thing we look for is tire wear patterns. A worn or ineffective shock absorber will usually cause a choppy wear pattern, often on just one side of the tire. The vehicle will bounce a lot too. Most of the time this symptom is accompanied by visible oil leaking from the strut or shock absorber. That's the second thing we look for during an inspection.

Replacing shock absorbers doesn't require an alignment because they don't have anything to do with the alignment. On the other hand, struts do affect the alignment on most designs, but not all. Your vehicle is one of the exceptions. The strut can be replaced without affecting the alignment, but there's one more important part involved. That is the coil spring which sets the ride height. All manufacturers supply published, legal measurements for every model. We get real picky about that because even though all the alignment numbers might look perfect on the computer's screen, there will still be greatly accelerated tire wear if ride height has sagged from weak springs. That's because all of the suspension system parts work together to hold the wheel and tire straight as it goes up and down and as you turn. With sagged springs, the geometric relationship of all those parts changes, then the wheels go through the wrong motions as you drive.

Weak / sagged coil springs are a matter of age. Strut wear is a matter of mileage. When it comes time to replace the struts, the coil springs have to removed from them, then they're reinstalled onto the new struts. A special compressor is required to do that as those springs have enough pressure on them to hold up that corner of the vehicle. There's a rather high degree of safety concern when working with springs that way. An alternative I eluded to in my very first sentence is there's an alternative now called "Quick Struts" that have been around for a number of years. Those are new struts with new coil springs already installed and ready to put on your vehicle with no special tools needed. This gets you the new strut, a new coil spring that will restore the critical ride height, and they have all new hardware. That hardware includes the upper mounting plate with a bearing assembly to make it easier to turn the steering wheel, and a bounce cushion to reduce the harsh shock you'd feel when running over big bumps. Those two items are just about impossible to inspect until the assembly is taken apart to replace the strut by itself, then we have to find you and tell you more parts are needed than we originally knew about.

With these Quick Struts, you'll pay more for them than for just struts by themselves, but less than if you bought the struts, springs, upper mounting plates, and bounce bumpers separately. While the assemblies cost only a little more than just the struts, you'll save a lot on labor cost because we don't have to transfer those old springs to the new struts. Overall cost is about the same, you get a higher-quality repair, and there's no safety concern from working with the compressed springs.

As I mentioned, your vehicle doesn't need to be aligned when the struts are replaced, but if you go with the Quick Struts with their new springs, a conscientious mechanic who has your best interest at heart is going to strongly recommend that alignment. One of two things will be found. Since the new springs will raise the vehicle, often more than an inch, which is a real lot to alignment specialists, the suspension geometry, and therefore the alignment, will have changed. We need to adjust the wheels back to specs.

The other possibility is the alignment was good years ago, then the suspension gradually sagged, putting the wheels out-of-alignment all that time. Now that the new springs got the ride height back up to where it was years ago, the wheels will fall back into proper alignment, just like they were years ago. This is more likely to occur if no alignments were performed during all those previous years. Most alignment shops have a lower charge then for an "alignment check", where they still have to set up and calibrate the equipment, but they don't have to struggle with any adjustments.