Can you use "regular" oil instead of synthetic oil?

How much would it harm the engine of a 2011 Toyota Camry to put "regular" engine oil in it instead of the recommended synthetic oil...

...if it was done just once?

...if it was done regularly?

You can use either oil if you change it more frequently. I use a pure synthetic oil and change in every 10k miles. If I used a dino oil, I'd change it every 3k. It won't harm your engine.

You can use either oil if you change it more frequently. I use a pure synthetic oil and change in every 10k miles. If I used a dino oil, I'd change it every 3k. It won't harm you engine.
Hi Brian, thanks for taking the time to answer. Your comments led me to Google "advantages of synthetic motor oil", and you were certainly 'spot on'. The articles I read said that synthetic oil breaks down more slowly than fossil oil, especially at high temperatures, and that also, because of its consistent viscosity even at low temperatures, provides good engine protection even when first starting the engine in extremely cold weather. So I can see synthetic oil is well-worth the added expense.

However, I'm curious about one thing: Does the above mean that an engine will run at a higher temperature in hot weather than it would when it's cooler?

No, as a general rule, engines in normal operating condition always run at the temperature determined by the thermostat, coolant flow rate, and quantity of coolant gallery deposit thickness/composition. They just test the oils at high temperature in the laboratory.

Also, some engines run hotter than others (different head design, fuel/air mixture composition, exhaust port and valve design, valve timing etc), so that makes the difference between the oils greater.

Not that it's really relevant, but I spent a few summers testing oxidation properties of various engine oils in a oil company research laboratory. The test consisted of bubbling oxygen through really hot engine oil in the presence of copper and iron. The quantity of oxygen absorbed was monitored.

Normal dino oils absorbed oxygen pretty fast and then all of a sudden they would go to hell once the antioxidant in the oil was used up. In contrast, synthetic oils absorbed oxygen much slower and went on forever. I never tested one to failure (owing to lack of interest on how long they would go). The real interest was in how long you could make dino oils last.

Although this test was good for comparing the oxidation properties of the various oils, it wasn't realistic for oil performance in an engine since every engine heats and contaminates the oil differently. Head temperature, fuel dilution (mainly for engines without fuel injection), acid buildup, metal contamination from engine wear, VI improver sheering, and other factors make each engine a special case.

Thomas,I have a 2013 Camry and it uses 0-20 synthetic and I have gone 10,000 on one change and 7,000 on another and never used any oil between changes,that aside I'm now locked into 7,000 between changes but I also read my owners manual about using or adding between changes ( if you have to add some other weight oil,you must go back to the original 0-20 on the next oil change ) It may have something to do with your Warranty.