Yes. There is no danger mixing synthetic and conventional motor oil. However, conventional oil will detract from the superior performance of synthetic oil and reduce its benefits. In this post, we’ll also look at if it’s safe to use regular oil after synthetic oil.
Let’s take a closer look.
Can I Mix Oil Types?
With synthetic lubricants continuing to grow in popularity, the question of whether synthetic and conventional oil can be safely mixed often arises.
I’m guilty of having mixed different types of motor oil with reckless abandon back in the day. A dash of synthetic-blend to top off my Buick Century one month and a shot of cheap conventional oil the next.
While oil performance probably suffered, my engine always remained in one piece.
That’s because you can safely mix synthetic and conventional oil. In fact, synthetic-blend motor oil is simply conventional and synthetic oil already mixed for you.
But, barring an emergency, it’s not a great idea to mix oil types.
Why It’s Not a Great Idea to Mix Synthetic and Conventional Oil
All motor oil, whether synthetic or conventional, is a combination of base oils and additives.
Synthetic base oils are manufactured using a process that removes the impurities inherent to conventional base oils. Synthetics typically contain higher-quality additives, too.
So, in the end, conventional and synthetic oils are comprised of the same, compatible components – it’s just that the components in synthetics are much higher quality.
While you can safely mix synthetic and conventional oils, you’re doing nothing more than diluting the performance of the synthetic oil.
What If You Have to Mix Oil Types?
You may not have a choice to mix the two in some cases.
If you’re traveling, for example, and suddenly find your engine low on oil, cheap conventional oil may be the only option at the gas station alongside the highway.
While it’s safe to top off an engine that normally uses AMSOIL synthetic motor oil with conventional oil, we recommend changing the oil at your earliest convenience. In fact, AMSOIL does not support extended drain intervals where oils have been mixed.
Can You Use Regular Oil After Synthetic?
Yes, it’s perfectly safe to switch to regular conventional oil after using synthetic oil. As mentioned, both oil types are made of compatible components; it’s just that the base oils and additives in the synthetic oil are higher quality.
But, since synthetic motor oil provides improved wear protection, engine cleanliness, fuel efficiency and other benefits, why would you want to use regular oil again?
I switched to synthetic in my 2015 Silverado 3500 dually. Been pulling a 44′ 5th wheel raptor with regular oil with no problem. After the switch at 37000 miles I started using oil. 1 qt after about 4000 miles. I’m a little disappointed
That’s easy. The problem is you’re driving a Silverado. Are you sure it’s not just leaking out of the pan like every other GM HD?
Hi John Baker,
I have a question can I use it in ATV?
Please let me know
Thank you
Yes, you can. In fact, we make a synthetic oil for ATVs and UTVs.
Use our online Product Guide to find the right viscosity for your machine.
Doug, Oil consumption can be caused by many different things. Check out the other story above on Oil Consumption.
I was using a synthetic blend but switched to a full synthetic oil in my 2008 Honda Odyssey that has 150K miles. Since I’ve switched I have to closely watch my oil level as I usually have to add a half quart every 2 weeks. I don’t see any oil leaks on my engine or driveway.
Why did this happen after switching to a full synthetic?
Hey John,
Can I use it to any vehicle?
Thanks
Hi Ronald,
Yes. Make sure to use the correct viscosity, however. And make sure the oil is recommended for the performance specs listed in your owner’s manual.
Thanks,
John
Hi John
Can I use the oil in SxS?
Waiting for your answer.
Thanks
Hi Joseph,
By “SxS,” I assume you mean side-by-side, or UTV. If so, yes, you can use synthetic oil. Check out our Product Guide for the correct AMSOIL synthetic lubricants for your machine.
Thanks,
John
Great post
Hey John Baker,
Great article! I’m using it, works great.
Thanks
After reading this article i tried it. It really works, nice tips.
Hi, John Baker
How safe is it to use synthetic oil to lubricate my compound bow?
Anticipating your response.
Hi Paula,
It depends. What does the manufacturer recommend regarding maintenance and the type of lubricant to use?
John
Can i top off my ride with bacon grease?
Can you? Yes. Should you? No.
Thanks,
John
Been watching Project Farm have we?
One reason could be that the synthetic “eats up” the gaskets and other components. Regular oil does not have that ability and actually the debri it produces helps the sealing of the engine from oil leaks. This is generally stated to be the case for older engines. Your car is pretty new and that should not be the issue; it is doubtful, but it may be also possible that your engine was not built specifically with synthetic in mind.
Hi VK,
I’m not sure why you think synthetics “eat up” gaskets and other components, but it’s not true. Synthetics pose no harm to gaskets, seals or other components. If it were true, would automakers increasingly recommend synthetics in their vehicles? Also, while engines are designed with a specific viscosity of oil in mind, they aren’t built to use a specific type of oil (e.g. conventional or synthetic).
Thanks,
John
Synthetic oils most certainly do not “eat up” gaskets and other components, maybe try changing the oil once in a while, that seems to be the problem here.
Wow lots of dumb questions I hope I don’t sound stupid but have posed this question to auto parts oil reps and they can’t give me strait answer. Ok there are about 5 syn oil base stock which one is best to worst and why and what brands types there are no labels on oil bottles.
Hi Joshua,
As it happens, we have a post on this topic. Check it out here.
Thanks,
John
It’s a great Oil I use ever, I’m using it more than 1 year, it really works great.
Highly recommend for every vehicle owner.
I currently have an older skidoo mineral oil in my unit. (Skandic) It’s a pao based oil. It’s OEM for the year (2003) but of course is no longer made other than the small supply I have on hand. Is the amsoil severe gear (75w140) compatible with this BRP pao base oil or would I need to do a full oil swap to ensure no tarring etc.
Hi Marcus,
SEVERE GEAR is compatible with synthetic (PAO) and mineral oils; however, for best performance we recommend trying to remove as much of the old fluid as possible before switching to AMSOIL.
Thanks,
John
Hi John Baker,
Can I use it for Polaris Ranger 900?
Please let me know
Thanks
Hi David,
If you’re asking whether we have products for your Ranger, yes we do. Use our Product Guide to find what you need.
Thanks,
John
Thank you for sharing this car maintenance guide. This could help me so much.
Do you make a marine oil for 150 mercury four stroke ?
Hi Dean,
Use our handy product guide to find the right oil for your Mercury.
Thanks,
John
Actually all conventional oil is going to synthetic blend. Mixture of conventional and synthetic.
Been driving for 50 years, and have always mixed or changed brands. Never had an engine go bad.
Actually all conventional oil is going to synthetic blend, Since I’ve switched I have to closely watch my oil level as I usually have to add a half quart every 2 weeks.
What is the best oil for motor bike?
Hi,
Of course we think the best oil for motorcycles is AMSOIL Synthetic Motorcycle Oil. You’ll see why in these two blog posts:
AMSOIL vs. Harley-Davidson Oil: How We Perform
See How AMSOIL Performs in the Harley-Davidson® Milwaukee-Eight® Engine
And, if you scroll to the end of this post, you’ll see why we think AMSOIL Synthetic Dirt Bike Oil is the best for your dirt bike.
Thanks,
John
Have leftover Quicksilver PWC 2 cycle oil
Can I sub for 2 cycle fuel mix oil for lawn care tools ?
Hi Frank,
In general, it’s best to use an oil specifically formulated for the application in which you intend to use it. We can’t speak for another oil manufacturer, so contact the oil manufacturer and see what they recommend.
Thanks,
John
thanks for article, i think it is better to not to mix these two type.
Went to have my oil changed in my Truck, (100,000 miles) wa told I needed high mileage oil. High mileage Oil?
Hi Benjie,
“High-mileage” oil is the fastest-growing type of oil today. It’s designed specifically for vehicles with (typically) 75,000 miles (120,000 km) or more. As engines age, seals can dry out and parts can wear if motorists haven’t be using a good synthetic oil and maintaining their vehicle. High-mileage oils contain extra additives designed to condition aging seals to help prevent leaks. Their viscosities also fall on the upper end of the spectrum to help seal the widening clearances between metal parts that are wearing over time.
While you don’t have to use high-mileage oil, especially if you’ve been using a good synthetic oil and performing proper maintenance, there’s no harm in doing so. If it were me and I knew I’d been properly caring for my engine, I’d thank the technician but continue using the oil I’ve always used (AMSOIL, of course for me).
Thanks,
John
Hi Mileage motor oil contains an additive for flat tappet camshafts. So if you are running that type of engine you should be running that type of oil. I collect old garden tractors. They are designed to run straight 30 weight oil with the old Kohler or Onan engines. I am using a break in oil that comes with that zinc additive in it. My 95 Jeep is designed for 10w40 with flat tappet cam. My snowblowers will probably get 5w30 hi mileage.
GM will tell you one quart in 4,000 miles is not excessive. I have 2 of the 6.3 trucks, both use about that much from new to now (about 150,000 miles). If you were changing oil by the “change oil” light or sooner and not checking the oil regularly with the dipstick, that loss would not cause the low oil level light to come on before a change. Many people when changing oils worry about added consumption and start checking the dipstick, revealing consumption that was always there.
I have a 2005 4runner -since new. It has 150,000 miles and runs great.
I tried synthetic oil in one oil change and got drips immediately, so I went back to conventional and change at 5000 miles.
The drips stopped completely 10 months after going back to conventional oil.
The exact same thing happened to me on a several of my vehicles.
Ted Winter; I read your comment about using zinc mixed in your motor oil. Personally I buy Rotella, because it has many good characteristics and for what you’re doing I would recommend the Rotella. I use a quart in my SS Monte Carlo after about 50,000 miles. Also helps with deglazing cylinder walls, and is a fairly high amount of detergents.
Regards…
Years ago my Instructor in auto mechanic when asked about mixing brands of oil (was before synthetic oil came along) said to always wrap the oil container with a rag when adding to car then car will not know what kind of oil you are using and will not care.
I am very glad to see this post. I will definitely share this post with others. Thanks for sharing.