RAVingLunatic said:
I've heard in the past that if you run synthetic oil that you have to start doing it from new. Any truth to this??? What are the benefits of synthetic vs dino?
It depends on the individual situation. The two main reasons that people say not to use synthetic on a higher mileage engine are 1- it may loosen up gunk in the engine and seep through the worn seals, and 2- synthetic is most beneficial if you use it from day one.
The first reason mainly depends on the state of the engine, because some engines will have no problems even if you switch to synthetic at 100K miles, while others may start buring oil faster because synthetic is more likely to leak past the seals on a high mileage engine. This half-truth is the foundation of the whole "you must run synthetic since new" argument. As for the argument over "once you switch to synthetic you can't go back to conventional oil", it is not true, but like the issue above, it depends on the individual engine. In the case of these arguments, they started as opinions and eventually became gospel.
The second reason is more of a benefit vs. cost issue (i.e. why bother to switch) and depends on the opinion of the user. The primary benefits of synthetic are realized over the long-term, and therefore it is most beneficial to run synthetic from when the engine is new. This is not to say that synthetic cannot provide some benefits on a high mileage engine, but many people just think it is a waste of money to switch if the engine has spent all of its life using conventional oil.
The main benefits of synthetic oil include:
- Longer oil change intervals
- Easier starting in cold weather
- Better long-term protection against engine wear
- Slightly improved fuel economy (sometimes)
- Some people claim it quiets the engine and makes it more responsive
As for the drawbacks vs. conventional oil, they are mainly the issue mentioned above (loosening up gunk and burning more oil) and also the increased cost of the oil itself.
The debate over synthetic oil is the same as the debate over premium gas; some people swear by synthetic and use it in all of their cars, while others think it is a waste of money unless they have a high performance car.