Synthetic vs. Conventional Oil: What Do I Use in My Small 4-Cycle Engine?

As I was walking through our Answer Center this week I overheard several customers asking about synthetic oils and should they be used in their Briggs & Stratton lawn mower engines. We’ve also had a few web chats regarding the same in the last few days, so here’s the scoop.

(Before I do, I gotta say: I love the fact that our customers care enough about their engines that they will call/email/chat with us before putting something new and different in the crankcase. I feel the same way!)

We all grew up on conventional oil which at its heart is crude oil which has been refined and then blended with additives. Most synthetic oils also start as crude but go through more complex processing down to the molecular level, resulting in a lubricant which offers a variety of benefits including:

  • Better wear control
  • Better viscosity
  • Better low temperature fluidity
  • Better deposit control

End result? By using a synthetic oil you are putting a better lubricant in your engine which helps reduce the risk of equipment failure and can extend its service life. The only downside is that extra protection comes at a higher price. Depending on the brand, synthetic oil can run almost double the price of conventional oils.

Some of the common questions people have asked us:

“Should I use synthetic or conventional (regular) oil in my 4-Cycle Briggs & Stratton Engine?

Our engines are designed to run on conventional oil, full synthetic, or synthetic blends. It’s an owner’s personal decision if the extra cost is worth the additional benefits synthetic oils offer. When a customer calls the Answer Center, we recommend the synthetic as it offers the premium protections we talked about earlier.

“Can I switch to a synthetic oil if I’ve always used conventional (regular) oil?”

There’s no reason you can’t switch to a synthetic oil if you’ve used conventional oil in the past. You do not need to flush your engine, or worry about the two mixing. The same goes for switching from synthetic to conventional.

“Does using a synthetic oil change how often I need to change or check my oil or break-in procedures?”

This is a common misperception of using synthetics in smaller engine. You need to continue your maintenance as stated in your owner’s manual regardless of the oil used.

(I like to use a toothpaste comparison: If you buy better toothpaste, you shouldn’t brush your teeth less or visit your dentist less often. But you do get cleaner teeth that last longer. Same for your engine: Runs cleaner and can make it last longer!)

“What temperatures are appropriate for synthetics?”

One the larger advantages of a synthetic is it has a broader range of temperatures where it should be used. A synthetic 5W-30 provides the best protection between -20 to 120° F (-18 to 38° C).  Refer to the following chart for a comparison:


“What brand do you recommend?”

I use and recommend Briggs and Stratton Synthetic Oil (Part# 100074WEB), as it is designed specifically for small engines on lawnmowers, tractors, generators, pressure washers, & outdoor power equipment. It can be purchased on our website or at your local Authorized Briggs & Stratton Dealer. If you are looking at other brands, make sure that somewhere on the label it states the oil meets or exceeds ILSAC GF-2, has an API certification, and lists “SJ/CF Energy Conserving” or higher before purchasing.

Here’s a candid snapshot of my Briggs & Stratton Pressure Washer and Synthetic Oil, right after checking the oil level and right before spraying off an extremely messy toddler’s high-chair:


I hope this helps in selecting the right oil for your needs the next time you are wandering around the store. Have a great weekend!

NOTICE: Customer service questions are not monitored via the blog. If you need assistance with your Briggs & Stratton engine or power equipment, please contact our Answer Center or post your question to our User Community.