Synthetic vs conventional oil: which one for Northern Nevada driving

Verdict

Synthetic is the better oil in a climate that swings from 26 F winter lows to 90 F summer highs and climbs from 4,400 feet to 8,900 feet on a weekend. Conventional remains the sensible pick for an older engine the manual rates for it, changed at the shorter interval.

The oil cap on your engine already tells you most of what you need: the viscosity grade and, on many newer cars, the word synthetic. If the manual requires synthetic, the choice is made. If it allows either, the question is whether Reno's climate and your driving make the upgrade worth it. This page lays out what each oil is, what independent testing says, and where each belongs.

What the two oils actually are

Conventional motor oil is refined from crude. Its molecules vary in size and shape, so it performs well in the middle of the temperature range and less well at the edges. Synthetic oil is built from chemically engineered base stocks with molecules of uniform size, then dressed with the same families of additives, so it keeps flowing when cold and resists breaking down when hot. A synthetic blend is a mixture of the two and sits in between; the blend vs full synthetic page covers that choice.

Both kinds carry the American Petroleum Institute's service rating on the label (API SP is the current gasoline category), and both are sold in the same viscosity grades. The grade on your oil cap is a requirement; the type, where the manual allows a choice, is a decision.

What independent testing found

AAA ran both oil types through the industry's standard engine-oil tests in 2017 and reported that synthetic oils performed an average of 47 percent better than conventional oils, with the biggest gaps in deposit formation, oxidation resistance and cold-temperature pumping. The same release reports that at AAA's repair facilities the price difference amounted to about $64 a year for an average driver, or $5.33 a month.

Consumer Reports' auto test center, in an article updated in January 2026, put the cost difference at roughly 30 percent more per change and noted that synthetic can run about twice as long between changes, which is why the annual cost often comes out close. Its advice, and ours, is to use what the owner's manual recommends.

Why the climate here tips the scale

Reno's airport averages a winter low of 26.9 F in December through February and a summer high of 90.2 F in June through August, with 65 days a year at 90 F or hotter and 122 nights at or below freezing (NOAA 1991-2020 normals). Our service centers sit between 4,426 and 4,917 feet (USGS), and a trip to the lake climbs past 8,900 feet at Mount Rose Summit. That combination, cold starts, hot afternoons and steep sustained grades, is what manufacturers describe when they define severe service.

Synthetic's advantage shows up at both ends: it pumps to the top of the engine faster on a frozen morning and holds its viscosity on a loaded climb. Conventional oil can do the job in the same conditions, but it has less margin, which is why the manual pairs it with the shorter interval.

Switching and mixing

You can switch from conventional to synthetic at any oil change, on almost any gasoline engine, and switch back later. The two are compatible, and a blend is proof of it. What you should not do is stretch the interval because the oil is synthetic; the interval is set by the manufacturer for the engine, not by the oil's marketing.

When you pull in, we read the cap and the manual, tell you which oils are an option for your engine, and put in the one you choose. The full synthetic and conventional pages describe each service, and any of the four service centers can do either while you wait.