Hazards of self-diagnosis

As vehicles get more complicated, new twists and more advanced multiplexing and technology only add to the challenges of diagnosing automotive problems. Yet in the world of auto repair, some customers don’t always perceive the valve in the cost of diagnosis. Throw in the fear of unknown and lack of trust into this equation, and some people start looking elsewhere for answers. The results most times are questionable.

Our shop technicians spend weekends and evening in classes to learn about the new technology. Newer vehicles are the most complex object that most people own and it is time consuming for technicians just to learn how to use new scanners and understand all of their capabilities.  In the past two weeks, four of techs spent Saturday and Sunday in classes.  

Recently, we had a customer bring in his European import with a check engine light on and running poorly. We hooked up a specialty scan tool, scanned the vehicle and found a P0301 code, misfire #1 cylinder. We called the customer asking for permission to spend time diagnosing the problem and what it would take to repair.

He called back and said he just wanted us to replace the fuel injector in the cylinder, saying that he had read it on the Internet. Very seldom do we find a fuel injector causing this problem but he said he was willing to take the risk. $245 later with a new injector, the vehicle still had the same problem. The owner then gave us permission to diagnose the real issue, which turned out to be two bad spark plug wires to that cylinder. (Yes, this vehicle has two spark plugs per cylinder). The customer was very understanding but we didn’t take out the injector because by that time it was used.

We had another customer request that we put a clutch switch in a Japanese import because the starter didn’t crank over on occasion even though we have never have replaced a clutch switch on that kind of car. It didn’t fix the problem.

Self-diagnosis also is a problem in the medical field, I have been told. But, I must admit that there is valuable information on the web, we use pay sites, $105 per month, which gives us direction. I repaired my motor home refrigerator from information in a blog about the problem I was having. But when it comes time to diagnose potentially complicated problems that could be expensive to repair, my advice is to trust the professional who is working on your vehicle.  Most times it will save time, money and aggravation.

How often to change oil?

One of the questions I come across as how often should you change your oil. This is a great question and I don’t have a black and white answer. There is no one size fits all answer other than to say oil should be changed frequently enough so that no engine damage is done.  

The low end is every 3,000, twice a year and there are some manufactures that do as high as 20,000 miles with no time recommendations!

There is one manufactory with high mileage recommended oil services that we have found an alarming amount of worn out engines at 80-90,000 miles.

 I will try and explain what I recommend is best. Cars before the year 2000 using conventional oil should have the oil changed every 3 to 5000 miles depending on how many miles you put on your vehicle per year. If you're putting 12 to 15,000 or higher miles on it a year every 5000 miles is fine but at least once a year in most cases.

If you have a car between 2000 and 2010 using conventional oil every 5000 to 7500 miles if you put over 10 to 12,000 miles per year but again, at least once a year.

If you have a car from 2010 to 2018 with synthetic oil and most newer cars take synthetic oil every 5 to 15,000 miles will work on oil services.

Now comes the exceptions is how do you drive and where the car is driven. Short in town mileage during the cold moist winters when the engine doesn't get warmed up is the most difficult on oil. Keep in mind, some of the combustion leaks past the rings in the engine fuel and moisture. This contaminates then mixes with the oil to create sludge and other harmful stuff in your oil. Twice a year or every 3,000 miles on this condition.

The 15,000 mile extreme on oil services would be if you did a lot of freeway driving, have a newer vehicle, use synthetic oil because you would be putting on 1 mile per minute at 60 miles an hour and keeping the engine warm or hot. 

There are many exceptions to these recommendations; the most common one is for folks with classic cars like myself. I have a 69 VW Karman Ghia.  It sits in storage most times, driven about 200-500 miles per year. I only drive it in the summer when not raining and at least 40 miles to get the oil hot. I change the oil every three to four years.

One thing is certain, In the long run, regular oil service is much more affordable than engine replacement. At the shops, we see a lot of wasted engines because of lack of oil services. 


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