Can I switch to synthetic motor oil and back to regular? Car Doctor

A: Synthetic oil has added benefits of improved lubrication, which helps minimize cold-engine wear. Also, synthetic oil will help with starting in cold weather and is more resistant to oil breakdown in hot weather.

As for switching, you can freely switch back and forth from synthetic to semi-synthetic to conventional oil without any issues.

I recently had Michael Thomas from Pennzoil on my radio show and talked about this very issue. You can find the Car Doctor podcast on johnfpaul.podbean.com or on most podcast sites.

Q: I have a 2008 Nissan Frontier V6 4X4 with a manual six-speed transmission that just hit 60,000 miles.

Four years and some 35,000 miles ago the ABS light came on, disabling the four-wheel drive. After a diagnosis at the dealership ($160) I was told the truck needed an ABS actuator. However, I was also told — as it was a manual transmission — the part was unavailable in the USA.

After contacting Nissan (in Tennessee), it took Nissan North America six weeks to locate one or have the original vendor make one. After spending $1,600 ($1,000 for the part and $600 for labor) the issue was fixed. Fast-forward four years and I have the exact same issue and am having the same problem with the part.

Nissan managed to locate two of the ABS actuators and I have now paid for the part in advance to get one. The truck is in great shape, and I have just replaced four tires with another pile of money.

Does this sound normal for a vehicle like this? I asked for some goodwill but was declined. Any ideas, or should I just drive the truck for a few years and cross my fingers before buying a new Toyota?

A: I suspect the replacement part was not any better quality than the original, which is why it had a relatively short life. Even though the truck is nearly 15 years old, with such low mileage I would be tempted to fix it and drive it, provided it is structurally sound (some Nissan products had serious rust issues).

Although $1,600 is expensive, with the cost of a new vehicle, that amounts to about three monthly car payments.

Historically, Toyota products have had fewer issues than Nissan trucks, but Toyota has had its share of problems with rust and engine as well.

Q: I saw your article about losing air in the tire. We had the same problem on my wife's car. After the shop checked it a few times over a few months, and we added new tires and valve cores and caps, I was finally able to figure it out myself. I sprayed soapy water around the valve stem. It took about 15 minutes to start bubbling. This might help someone else.

A: Thanks for the suggestion. Some shops will — when changing tires — rebuild the tire pressure sensors. This includes a new cap, valve core and the rubber seal around the metal stem. Pre-tire radio frequency pressure monitors, nearly all new tires got new valve stems. The new valve stems solved many tire leaks.

Q: My 2013 Nissan Rogue has about 73,000 miles on it. I change the oil regularly. The car starts fine, but once I use the car, I have to wait at least 20 minutes or more to use again. It won't start. It makes a cranking sound but won't catch. After 20 minutes or so, it starts right up and runs fine. What can be wrong?

A: What you are referring to is known as "hot-soak." For an engine to run, it needs engine compression, fuel and spark. If one of these items is missing, it won't start.

At this point, the first thing to do is check the battery, cables connections and grounds. A poor ground could be the issue, not providing voltage to the ECM.

Some other possibilities are faulty crankshaft position sensor and even an ECM (computer) that is being affected by the heat.

Best to leave it with a shop so they can hook up test equipment and test the engine after it has been running.

John Paul is the AAA Northeast Car Doctor. He has more than 40 years of experience in the automobile industry and is an ASE-Certified Master Technician. Write to John Paul, The Car Doctor, at 110 Royal Little Drive, Providence, RI 02904. Or email [email protected] and put "Car Doctor" in the subject field. Follow him on Twitter @johnfpaul or on Facebook.