Can you put conventional oil in after synthetic

This is a myth. A lot of old-school mechanics and non-chemistry educated people repeat this false myth.

When changing from synthetic to regular oil, there is not anything special that you need to do because synthetic oil will mix directly with regular oil of the same weight (no engine flush is needed).

There is some differences between synthetic and regular oil. Synthetic oil has detergents and chemicals to protect the longevity of your engine.

ericthecarguy.com has a great YouTube video that talks extensively about the differences of synthetic vs regular oil and answers lots of common questions:

[2013-02-04 Regular Oil vs Synthetic Oil -EricTheCarGuy]( http://www.youtube.com/watch?v=3zEBI1QndPo)

A Valvoline scientist publicly stated switching from synthetic oil to regular oil not do anything to your engine. Additionally Valvoline has a public website that states this myth is false https://www.valvoline.com/about-us/faq/synthetic-oil-myths :

*MYTH: Once you’ve used synthetic motor oil you can’t switch to conventional motor oil. * Not true. Synthetic and conventional oils are compatible, so it is not harmful if you decide to switch."

Even Mobil1 reps agree with it. Trust me, this has been such a topic of issue; They just decided why not put the myth to the test. So, you should be fine. Your engine may get dirtier quicker, and the oil should be changed more often, but other than that you'll be fine.

update- After researching what Paulster2 commented on my reply, he is right. You shouldn't need to do a flush. He also commented a link to a guy is well versed in the subject. So I was wrong about that.

This article has been updated from its original 2015 version.

Q: Can conventional and synthetic oil be safely mixed?

A: With synthetic lubricants continuing to grow in popularity, the question of whether synthetics and conventional oils can be safely mixed often arises. Yes, you can safely mix synthetic and conventional oil. 

All motor oil, whether synthetic or conventional, is a combination of base oils and additives. Each are designed to be used in the same applications, so they each pass the same minimum standards. The main difference is conventional oil is typically designed to just barely meet standards while reducing the cost as much as possible.

Synthetics, on the other hand, usually surpass the minimum standards, and they typically contain higher-quality additives, too. In the end, conventional and synthetic oils are completely compatible. However while you can safely mix synthetic and conventional oils, you’re diluting the performance of the synthetic oil.  In fact many companies premix them, calling them synthetic blends, and sell them as a mid-grade performance product.

Information provided by: Amsoil

When you have a question about motor oil — and this is an important one! — you’ve come to the right place. After all, Jiffy Lube® knows oil. Every day, trained Jiffy Lube technicians help thousands of motorists select the right motor oil, and that includes choosing synthetic vs. regular oil and advising whether mixing motor oil is okay.

So, can you mix synthetic oil with regular oil? Yes. If it’s something you do only occasionally, mixing shouldn’t damage your engine. Let’s say you want to top off your oil, just to keep you rolling until your next regularly scheduled maintenance check. Mixing is alright, if the oil you use is the weight (or viscosity) recommended in your owner’s manual.

BUT JUST BECAUSE YOU CAN DOESN’T MEAN YOU SHOULD

To better understand why mixing motor oil is not recommended as a regular practice, let’s take a closer look at motor oil and what it’s designed to do.

Oil circulates through the motor, lubricating the motor’s moving parts to help reduce friction and prevent components from overheating. Motor oil also picks up deposits and contaminates so they can be filtered out, keeping your motor running smooth and clean. 

The question, “can you mix synthetic oil with regular oil” implies there are only two types of oil. But really, it’s more complicated than that. Most Jiffy Lube® locations use Pennzoil® motor oils that fall into these four basic varieties:

• Conventional or Regular motor oil. Derived from crude oil, conventional motor oil often works best in vehicles with simple engine designs.
• Synthetic motor oil. Synthetic motor oil is chemically engineered, so the molecules are more uniform in size and shape. The result is that synthetic oil tends to have fewer impurities than conventional oil. Synthetic oils are usually specially formulated with additives to enhance performance in extreme temperatures.
• Synthetic blend motor oil. A mixture of synthetic and conventional oils, it can resist oxidation and rust better than conventional oil. This makes it a popular choice for driving in extreme cold or wet weather.
• High-mileage motor oil. Formulated to reduce oil burn-off and leaks, high-mileage oil was created for late-model vehicles or newer vehicles with over 75,000 miles.

As you can see, each of these oils is scientifically formulated. Mixing them will not improve the performance or efficiency of your engine in any way. Nor will mixing improve the oil performance, either. This is illustrated by these two equally important points:

1. Adding synthetic oil to regular motor oil will not enhance the regular oil
2. Mixing regular motor oil with synthetic oil may dilute the benefits of the costlier synthetic oil

When you consider that synthetic motor oils are typically more expensive than regular or conventional oils, mixing them is a waste of your hard-earned money. By diluting the advantages of the synthetic oil, you may experience less engine protection.

REMEMBER, THE MIX IS JUST A SHORT-TERM FIX

To review, if you find that you have to top off your motor oil and the only convenient and affordable option is to mix synthetic with regular motor oil, it’s okay. But it’s not great and it shouldn’t become a habit. After you top off your oil, why not contact Jiffy Lube® and schedule a Jiffy Lube Signature Service® Oil Change so your vehicle will get the professional care it deserves?

Now that you’ve got the answer to “can you mix synthetic oil with regular oil,” you may be wondering …

WHAT ABOUT MIXING ENGINE OIL BRANDS? 

Yes. It won’t harm your engine to mix, for example, Quaker State® motor oil with Pennzoil, as long as the oil you use is the weight (or viscosity) recommended in your vehicle owner’s manual.

CAN YOU SWITCH BACK AND FORTH BETWEEN MOTOR OILS

There’s an old wives’ tale that after you go from regular to synthetic oil, you can never go back. That’s simply not true. But before you make a switch, refer to your vehicle owner’s manual. It will specify the viscosity (or weight) of the oil you should use. Did you know that you risk engine damage — and could even void your new-vehicle warranty — if you don’t follow manufacturer recommendations? If you can’t find your manual, or if it gives you a choice of options, you can always ask a Jiffy Lube® technician. They can access most vehicle owner’s manuals, and they know oil.

THE BEST TIME TO MAKE A SWITCH IS DURING AN OIL CHANGE

When you bring your vehicle to a nearby Jiffy Lube® location, you can count on having a conversation about your oil change. You may be asked if you:

• Drive in stop-and-go traffic
• Drive in extreme temperatures
• Drive at prolonged higher engine speeds
• Take multiple trips averaging only 5 to 10 miles in length
• Tow and/or haul heavy loads
• Drive in dusty or muddy conditions
• Drive in mountainous terrain

Based on your answers, as well as manufacturer recommendations, the Jiffy Lube® technician will explain the motor oil options for your particular vehicle. After you two discuss your choices, you can make a smart selection, based on solid information, not guesswork.  Then the trained technician will:

• Remove and safely dispose of the used oil
• Replace it with new oil that meets the manufacturer recommendations for type, weight, and volume
• Dispose of the dirty oil filter and replace it with a fresh, clean one
• Top off vital fluids — including transmission, power steering, differential/transfer case, and washer fluid
• Vacuum the interior of the vehicle and clean the exterior windows

If you’d like, the technician will place a sticker in the upper left corner of the windshield to let you know when your next oil change is due. Or, if you have a message center that displays oil life, the oil life monitor will be reset to reflect your new oil change.

YES, JIFFY LUBE KNOWS OIL … AND A WHOLE LOT MORE

When you have an automotive question, turn to a Jiffy Lube® technician. They have been rigorously trained in preventative maintenance and can help you keep your car, SUV, minivan or truck out of the shop and on the road, where it belongs. 

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Here’s an overview of services — from batteries and brakes to vehicle inspections — that Jiffy Lube® provides.

This article concentrates on the differences between synthetic and regular (aka conventional) oil.

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Please note: Not all services are offered at all Jiffy Lube® service centers. Please call ahead or check jiffylube.com to ensure the service is available.
 

Is it OK to add conventional oil with synthetic?

What happens if you mix conventional and synthetic?

Can I switch back to conventional oil?