Why can’t you use regular oil after using synthetic?

In all lies is a grain of truth. Early in the days of synthetic, the compounds in the oil had different effects on the internal seals of an engine. Petroleum contained distillates that caused the engine seals to expand or “swell”. The seals would wear to the correct tolerance for that component and everything would be fine, until the owner switched to synthetic oil . Synthetics did not contain the distillates and the seals would return or “shrink” back to their original size.

This caused sometimes incredible oil leakage issues. An interesting side bar is the invent of several “stop leak additives” to battle these problems. The primary component of these was and still is today…. Petroleum Distillate

If an engine had synthetic oil in it from the beginning and for the majority of its existence, the seals would not swell and wear until the owner switched to conventional oil. Once the switch was made, you could never go back due to the extended wear to the motor.

Both synthetic and conventional oils are “engineered” today making them very similar in detergent and distillate levels, so switching is not so much of an issue anymore.

Synthetic Or Regular Oil

When you change your oil if you used synthetic instead of regular conventional oil thats fine. It well help you have a cleaner engine. The synthetic oil will burn better and it won’t burn as fast as regular conventional oil.

1. I believe what you heard is that you can’t switch from synthetic back to regular conventional oil any day of the week.

2. It is recommended that whatever type of oil you use when you get your oil change that you stick with that type of oil until the next oil change.

3. During your next oil change you can switch to a different brand or type of oil if you so choose.

Hope this helps!!

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RE:

Why can’t you use regular oil after using synthetic?

I have been told that if you start using synthetic lube oil, you must continue. Going back to regular oil will damage the engine. That does not make sense to me.

Not true. I don’t know why you would want to switch but synthetic does keep a very clean engine. So if you switch and you have changed your oil every 3k miles or so you will not have the regular gunk build up in the engine. This and the fact that regular oil burns faster, you will need to watch the oil level frequently to make sure you do not get too low. Expect your oil comsumption to increase, but this will not damage the engine.

I just read an article at Valvoline website. It is an oil maker and is aggressively selling its synthetic oil. Yet, in the Q&A section regarding this switching back or back and forth between conventional and synthetic oil, Valvoline says “THERE IS NO PROBLEM” at all.

Another thing that is very important, synthetic oil IS NOT intended to lengthen the usage time of the oil. If the engine manufacturer’s says you should change oil at every 5K miles, change it at 5k miles. The dirt or debris that comes from air or engine parts cannot go away by itself. Just like any other detergent, you should flush it away after certain degree of dirt concentration.

Never heard that. I’ve heard the other way from several mechanics. They say going to syn after you’ve used conventional for years will cause leaks because the syn molecules are so much smaller they find ways out that conventional oil has left from wear and tear.

If that is the case why do they make a synthetic blend which is…….blended with regular oil? I think it’s a myth. You can change back to regular oil as long as it meets the regulations of your car manual.

It doesn’t make sense because it is not true. Use what you want provided the manufacturer does not require synthetic, just be sure it is the proper viscosity, (5W30 etc..).

You can switch and even mix your oil anytime. Use the viscosity for you car. Most oil change places use a blend or you can buy blended oil at the store for DIY.