Motormouth: Oil specs keep changing

By Bob Weber

Tribune News Service
November 24, 2023 at 2:15PM
(iStockphoto/The Minnesota Star Tribune)

Q: If it is stored properly in unopened containers, does motor oil, either synthetic or conventional, deteriorate over time?
A: The bigger risk is that as standards change, it will become obsolete. Compare the API classification against what your engine requires. That information is on the engine's oil fill cap.

Viscosity characteristics are important, but it is not the only factor to consider when choosing a motor oil. The second thing to look for on the API doughnut is the service classification, which helps determine the ratio of oil properties to its operating conditions.

The first API Service Classification of motor oil was SA. From there, as motor oil improved and met increasing specifications for newer cars, the classification moved to SB, SC, SD, and so on (skipping SI and SK).

Cold affects pressures

Q: Last year my tire sensor light came on, but when the dealership checked the tires, the inflation was fine. They replaced a tire sensor. This week the light again came on again, and, again, the tires checked out fine. Is this a defect in my 2014 Subaru? While in the waiting room at the dealership to have the tire sensor replaced, I encountered another person who had the same problem.
A: At this time of year, low tire pressure warnings go viral. The sudden drop in temperature lowers the pressure. For every 10-degree drop, tire pressure goes down 1 psi. Often, by the time you drive to a dealership or tire store, the tires have heated up, increasing the pressure. Adjust your tires to the manufacturer's specs when they are cold.

A fortunate mistake

Q: I have a 2020 Honda CR-V that had a recent oil change. I have been using regular conventional oil, but messed up and asked for synthetic oil. Have I done any damage? My owner's manual says: "May also use synthetic oil. ... " Also, should I do anything right now if this is a bad thing? Should I do something different at my next oil change?
A: You did not do a bad thing, but a good thing. Synthetic motor oil provides better protection and lubrication, which reduces wear on the engine's components. Reduced friction improves fuel economy. Synthetic oil also works better than conventional oil during severe hot and cold conditions. The downside is the higher cost. In my opinion, it is worth it.

Kit update

Q: You recently mentioned emergency kits. I learned the hard way that another good item to have in it is a pruning saw, just in case you encounter a downed tree with limbs blocking a lonely, country road. It could save you a long detour.
A: Good idea. The readers seem to burst with them. The list probably could go on ad infinitum.

Bob Weber is a writer, mechanic and ASE-certified Master Automobile Technician. His writing has appeared in automotive trade publications, Consumer Guide and Consumers Digest. Send automotive questions along with name and town to motormouth.tribune@gmail.com.

about the writer

Bob Weber