Q: Dear Tom and Ray:

Remember how, in the 1950s, a quart of oil would have API designations like "MS," "DG," etc.? Now I see letters like "SJ," "SH" and "SG." Do these letters mean different breakdown temperatures or different additives or what?

-- Bob

A: RAY: Yes. The letters refer to a set of voluntary standards administered by the American Petroleum Institute (API). They cover various oil properties--lubricity, breakdown temperature, particle suspension, etc.

TOM: Every so often, the API people--in consultation with the oil industry and carmakers--raises the standards. And when they do that, they assign the new standards a new set of letters.

RAY: For gasoline engines, the first letter is always "S."

TOM: Wait a minute. Why is it "S" for "gas"? Wouldn't it make more sense to use "G" for "gas"? Am I missing something here?

RAY: That's a closely held trade secret. Anyway, the second letter goes down the alphabet as the standards get more current. So "SA" was the first standard. The current standard, introduced in 1996, is "SJ."

TOM: And for diesel engines, the designations probably all start with "Q," right?

RAY: No, "C."

TOM: Ah! Remind me to discuss the sorry state of the American educational system with you someday.

RAY: "CH-4" is the current diesel standard, having been introduced in 1998.

TOM: The other question we get about these letters is "Can I use an oil with an outdated standard in my car today?"

RAY: The question usually starts out: "I just found a bunch of 'SF' on sale for 13 cents a quart (or I just inherited a case of 'SF' from my late Uncle Marty). Is it okay to use it, even though today's standard is 'SJ'?"

TOM: And the answer is yes, it's fine as long as your owner's manual calls for a standard of "SF" and not something better. If it was good enough when the car was new, it's good enough now.

RAY: But if your owner's manual specifies something more current (in this case "SH" or "SJ"), then use Uncle Marty's old oil in your lawn mower . . . or on your salad.

Dear Tom and Ray:

The power door-lock solenoids in my mother's 1989 Toyota Camry burned up while she was in the car. She had to climb out the window to escape. My father had to remove all of the solenoids himself so the doors would operate manually. Toyota said at the time that it had never heard of such a problem and charged us $900 for the repair. I've heard that Toyota has since issued a recall. Any advice?

-- Hugh

TOM: Yeah, write to Toyota and ask for your 900 bucks back. If you don't have the receipt anymore, your dealer may still have it--or you may have a canceled check or credit-card statement.

RAY: Toyota certainly did have a problem with these solenoids (the tiny electromechanical activators that operate things like power door locks). In fact, I even remember customers being advised by their Toyota dealers to carry a brick with them at all times so they could escape the car in case of emergency--since sometimes the power windows failed, too.

TOM: Toyota did issue a recall and fixed this for free on the affected Camrys. (If you want to know if your particular make and model has been recalled, get a free "Car Talk Car Report" at our Web site, the Car Talk section of www.cars.com.) The fix involved adding an additional sub-relay to the system to prevent it from locking up, and it seems to have done the trick.

RAY: And if you paid for the repair of a federally recalled item, you're entitled to a refund from the manufacturer. Tell 'em you'll trade 'em your brick for $900.

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