Talking Cars: Need to know about car oil

Junior Damato

QUESTION: I appreciate your column. My question is about use of full synthetic oil 5W30 of which I have a supply (Mobil brand). I am a certified aircraft mechanic and will be changing the oil on my daughter’s 2004 Ford Freestar van 4.2 liter with over 100,000 miles. The problem is, Ford specifies use of 5W20 oil. Do you believe I can use the 5W30 with no problem? A quality 5W20 oil has always been used. I thank you in advance.

ANSWER: This is a great question for all readers with any type of vehicle. I have been in the auto repair business for 40-plus years and seen a lot of changes. Engine oil is a big part of the change, as are all the internal engine modifications. Today’s not only have a lot of electronics on the dry outside of the engine, there is also a lot inside that have oil flowing through them whenever the engine is running. Now more than ever it is very important that the correct oil viscosity is used as well as changing the oil at the suggested intervals or sooner and not let the oil level go down. I have seen many variable oil controlled valve solenoids that have failed from oil clogging. As for your older vehicle with the high miles, the use of the 5W30 would not cause any problems. Some engines use 0W30, especially in cold climates. There are also more vehicles coming out of the factory with full synthetic oil. As always, I still recommend the use of full synthetic oil and changes at 6,000 miles under most conditions. I still see a lot of import vehicles with oil change intervals at 10,000 plus miles.

QUESTION: I own a 2003 Ford F-150 with a 4.6 liter V/8. The problem is intermittently the temperature gauge goes too hot and there are no signs of the engine overheating. If I shut the engine off and restart it again the temperature is normal. I have also replaced the thermostat and cylinder head temperature sensor. The check engine is also on. Do you have any ideas?

ANSWER: I have seen this problem as well as speedometers, tachometers that cannot act properly due to faulty ignition coils. My first encounter with this problem took me to our friends at Identifix, and sure enough there were other technicians that had run into the same conditions. The ignition coil specs are found in the Alldata website. To verify and check the condition of ignition coils, a professional scan tool that has the mode six option is needed, not just a scan tool reader. The faulty ignition coil spikes the computer and causes the problem and can also cause faulty readings on the speedometer and tachometer.

QUESTION: I own a 2006 VW Passat that the check engine light is on and sets a code for the front oxygen sensor stuck rich. My technician said the problem is just a faulty oxygen sensor, so I replaced it. The next day the check engine light came back on and the same code came back. Do you have any ideas?

ANSWER: I see a lot of four-cylinder VWs with vacuum leak problems that cause the check engine light to illuminate. VW, like a lot of manufacturers, uses hard plastic tubing to connect a number of both vacuum and evap devises. Over time these plastic tubes get even more hard and brittle, and crack and leak. VW also uses a plastic valve on the front side of the valve cover and a metal tube that has a check valve also for engine breathing that I have seen fail on a regular basis. This will cause a lean condition and the oxygen sensor to stay in a rich mode. The technician will check for vacuum in the crankcase by removing the oil dipstick and checking to see how much vacuum there is. There should only be an inch of vacuum. Any more indicates a vacuum problem causing the oxygen sensor to be stuck in a rich condition. Have the technician check the Identifix and Alldata website for all needed repair information.

Junior Damato writes regularly about cars. You can send questions to him care of the Old Colony Memorial, 182 Standish Ave., Plymouth, MA 02360. He can be heard live on WXBR radio 1460, 7-10 a.m. Saturday mornings.