Dear Tom and Ray:

In the past six months or so, four auto-repair shops that I sometimes use (including a Toyota and Subaru dealership) have started to heavily promote additives. They claim that $43 worth of additives for fuel, oil, coolant and transmission (identified as BG30K and BG525) would lower wear and tear on these systems, plus provide other benefits. The auto manufacturers I checked with are cagey about these additives, saying they think the additives are a good idea, but they don't officially recommend them. Since the costs of these additives add up over time, I'd like to know if they're worth it, or if they're just a new profit center for repair shops. -- Dennis

RAY: It sounds like a profit center to me. And I'm going to look into it as soon as I get back to the garage, Dennis!

TOM: Actually, we know some Subaru dealers who recommend an oil-cleaning additive. Maybe they've found it helpful. Or maybe they just want the extra eight bucks' profit on each oil change?

RAY: But we don't recommend additives to our customers unless they're trying to treat a specific problem. There are certain situations where additives can be helpful. For example, BG, which makes the additives you mention, also makes stuff called "44K," which we find to be terrific for cleaning gunk and carbon off of valve trains and out of fuel injectors.

TOM: We're not familiar with BG30K. I suspect the nomenclature refers to potential profits (i.e., the average shop makes only $30K a year pushing BG30K, while it can clear $44K on the valve-train cleaner).

RAY: So, I'd skip it, Dennis, unless the manufacturer specifically recommends it, or unless your mechanic is trying to solve a specific, diagnosed problem.