Can I switch to synthetic engine oil and back to regular oil?

Q: I have a 2008 Toyota Highlander V6 Limited Edition with 74,000 miles, which runs great. Can I switch to synthetic oil if I had used conventional oil since the car was new? Is there a benefit to changing the oil at this point in the age of the vehicle? If I change, I was told I couldn’t go back. Is it true?

You can freely switch from synthetic oil to semi-synthetic oil to conventional oil without any problem.

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

As for the change, you can freely change from synthetic oil to semi-synthetic oil to conventional oil without any problem.

I recently had Michael Thomas of Pennzoil on my radio show and talked about this problem. You can find the Car Doctor podcast at or most podcast sites.

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

Four years and some 35,000 miles ago, the ABS light came on, disabling all-wheel drive. After diagnostics at the dealership ($160), I was told the truck needed an ABS actuator. However, I was also told – as it was a manual transmission – that the part was not available in the USA.

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

Nissan managed to locate two of the ABS actuators and I have now prepaid the part to get one. The truck is in great condition and I just replaced four tires with another stack of cash.

Is this normal for a vehicle like this? I asked for goodwill but was refused. Any ideas, or should I just drive the truck for a few years and cross my fingers before I buy a new Toyota?

A: I suspect the spare was no better quality than the original, which is why it had a relatively short lifespan. 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 was structurally sound (some Nissan products had serious rust issues).

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

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

Q: I saw your article on air loss in the tire. We had the same problem on my wife’s car. After the shop checked it several times for a few months and we added new tires, cores and valve 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. It 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 gasket around the metal stem. Pre-tire radio frequency pressure monitors, almost all new tires have new valve stems. New valve stems solved many tire leaks.

Q: My 2013 Nissan Rogue has about 73,000 miles. 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 it again. It does not start. It makes a starting noise but does not catch. After about 20 minutes it starts up and works perfectly. What’s wrong ?

A: What you are referring to is known as “hot dipping”. For an engine to run, it needs engine compression, fuel, and spark. If any of these items are missing, it will not start.

The first thing to do at this point is to check the battery, cable connections and grounds. A bad ground could be the problem, not supplying voltage to the ECM.

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

It’s best left at a shop so they can hook up the test equipment and test the engine after it’s run.

AAA Automotive Physician John Paul

AAA Automotive Physician John Paul

John Paul is the AAA’s Northeast Automotive Physician. He has over 40 years of experience in the automotive 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 and put “Car Doctor” in the subject field. Follow him on Twitter @johnfpaul or on Facebook.

This article originally appeared on The Providence Journal: Can I switch to synthetic motor oil and go back to regular oil? car doctor


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