I was recently told by, a dealership service department, that they would not put synthetic oil in a car with less than 15,000 miles. Since they had my car, I decided not to antagonize them by asking for a explanation. The owner’s manual has nothing to say about this, except that synthetic oil (of the correct viscosity) is acceptable, but not required.
So, doper gearheads, is there a reason to not use synthetic oil early in an engine’s life? If there is, why wouldn’t the manufacturer give a warning to that effect?
What I’ve heard is that synthetic oil can impede break-in wear. My understanding is that it lubricates in a way (too efficiently?) that doesn’t allow the piston rings and cylinder walls to wear together for an optimal matched-to-each-other fit. With the rings thus not seated properly, the engine tends to burn oil.
Whether this is still the case, I don’t know. There was a day when manufacturers had specific instructions for how to drive during the break-in period so as to seat the rings, often coupled with a low-mileage (e.g. 1000) first oil change. With modern designs and materials that doesn’t seem to be necessary any more. It may be that the dealer’s advice is based on experience and remembrance of those days. Obviously, it’s not an issue with cars that require synthetic oil and come with it as their factory fill.
I have a very strong opinion about synthetic oils. If you have an old beater and you change the oil every 3k to 5k miles anyway, don’t use synthetic. It isn’t worth the extra $ you pay. For a new car however, I’ve switched every new car to synthetic on the first oil change. Most manufacturers recommend oil changes at around 7k these days. Many cars also have oil condition monitors in the engine so it will tell you when to change the oil - this is true of my 2004 GMC truck. I change the oil at about 9 - 10k (when the monitor says to because it is still under warranty). I am a big believer in synthetic oil and if you do some research on the differences, I think you may become one as well.
Almost all car manufacturers these days have the machining of engine parts down to a gnat’s ass, so the tolerances don’t need the kind of break-in that they once required.
Break-in during the old days was very specific. I remember Dad bought an Olds 88 in August of 1942 (great car, too - would do over 100, at least on the speedometer) and the break-in included no speeds over 35 mph for the first 500 miles. That would be fun on the freeways today.
It says that it’s a mineral oil with high concentrations of phosphorus and zinc which protect the engine. The latest ACEA C3 specification for Euro 5 cars calls for very small concentrations of phosphorus. Using these oils on engines that haven’t been broken in or older technology engines is not recommended.
Do not let this dealership person work on your car. Modern engines do not need any sort of extended break-in period, other than being mild with it for the first 500 miles. No full throttle starts, high speeds, etc.
The statement about not putting synthetic oil in until 15000 miles would have been partially true 25 years ago but does not apply to the new engines today.
The oil filler cap on my car specifies synthetic oil only.
A sidenote note to this topic, NASCAR teams using Toyota engines built by TRD ran into some problems early in the season. TRD was using synthetic oil during break in and dyno testing of it’s newly built engines. When these engines were put on the race track, the engines began failing at an alarming rate. It was discovered that the synthetic oil was not letting the lifters and camshafts break in properly causing lifter failures which in turn resulted in engine failure. A simple change to regular oil during break in eliminated the problem.
If he excluded mechanics that believe old wives’ tales about motor oils from working on his car, he’d probably knock 75% of them out of contention.
Most mechanics are very good at their jobs, but like 99% of people out there, most mechanics don’t really understand viscosity, mixed summer/winter grades, oil additive package types, the difference between synthetic and conventional oils, etc.
It actually takes weeks of study to truly understand the above topics.
Many new cars come from the factory with synthetic in them. If you want the straight dope for your car, I suggest that contact your car maker’s consumer help line and ask them. They will have access to the factory guys and you will get the straight answer.
Some cars depend on the properties of synthetic oil for engine timing (BMW). The point made above about NASCAR actually reinforces the fact that modern engines coming out of the factory can have synthetic or regular oil, but if it REQUIRES synthetic, USE IT, as it plays a critical role in more than lubrication.
Back to NASCAR engines: these ARE indeed ‘old school’ engines. I would expect that break in is critical, just like the old days, boys. Cooter works up the engine real nice by hand, and break in is going to dictate how well she performs. I am not surprised that a NASCAR engine would need a critical set of steps to break in properly.
Onto current engine break-in periods: Probably less about internal engine components and more about engine computers learning to adapt, fresh belts and break pads breaking in and ‘seating’ properly, and even tranny computers adapting to different needs and characteristics. Just not about the internal components.