As some of you know, I run my 2003 Nissan 350Z non-competitively on racetracks as a hobby. Naturally I do my best to take very good care of it.
At the beginning of every season, I have my dealership replace all the fluids: oil, coolant, brake fluid (with special high-temp fluid), power steering, differential, etc.
The service dept. wants to flush some of those fluids instead of simply draining and replacing them. Supposedly the big flushing machine removes all the old fluid and gunk and that’s supposedly better. In the case of the coolant, it costs an extra $100.
So is it worth it? Why or why not? If so, for which fluids?
Thanks.
(FYI: I replace the oil and the brake fluid more often than once a year. This is just the start-of-the-year service.)
Oil: Virtually no benefit to flushing if it is changed regularly and thus has no sludge buildup. Potential harm from flush solvent temporarily removing protective oil film. At least some vehicle manufacturers specifically advise against flushing oil.
Coolant: Flushing is advisable, but does not require machine or expensive procedure. Can be done well with water from a garden hose, best if block drain is opened. Flushing machine may be beneficial if block drain is inaccessible. Recommendation for conventional coolant is typically 2-3 years/30,000 miles. Acidity of coolant (pH) can be tested to see if coolant needs changing.
Automatic transmission: Is an alternative to traditional drain, refill, & filter replacement procedure. Has the advantage of replacing virtually all the fluid instead of 1/2-2/3 of it, disadvantage of not replacing the filter.
Manual transmission, differential: Hah! Mimimal if any benefit beyond standard drain & refill.
Power steering: I’ve only seen fluid replacement recommendation from one manufacturer (Isuzu) - others do not list it in the maintenance schedule. Probably has some benefit, but jillions of vehicles go their whole lifetimes without any problems that can be attributed to deteriorated fluid. Probably not cost-effective.
Brake fluid: Simple replacement of fluid from master cylinder reservoir on down effectively flushes system, special machine not required.
Various flushes are often vigorously promoted by quick-lube shops (and others). Many in our trade believe they’re oversold and call them “wallet flushes.”
