Synthetic Oil

I have a 2006 Toyota Corolla with 118,000 miles. I use synthetic oil during oil changes and change the oil every 5,000 miles. My mechanic implied that at 6,500 miles the oil was in pretty bad shape and needed to be changed. Am I being ripped off? I understand that synthetic should go 10,000 miles.

Ripped off is so accusatory. Look at the oil on a white paper towel afteryou check the level. Is it the color of honey or molasses? Is it low?

Unless you do an oil analysis, neither you nor your mechanic really know. 5K miles with synthetic is relatively conservative. I run 5K miles on conventional and 7.5K miles on synthetic in my cars. Have had no issues in any of my vehicles, and I routinely keep them 150K-250K miles – no engine or lubrication issues.

On the other hand, not all synthetics can go 10K miles, either. You may want to visit and read some of the used oil analyses there.

What does your owner’s manual say? I would guess 7500 on conventional.

I think synthetic can easily go 10,000 miles.

Like Jayhawk said, appearances really say nothing about the oil’s condition. Me, I change at 5,000 - 7,500. And your mechanic isn’t trying to rip you off, opinions vary widely on miles between changes. What does you owners manual say?

You’ll probably be money ahead just using regular oil (if allowed) at the specified interval.

Different oils, cars, engines, all can call for different oil or change schedules. Let’s start with what the manufacture recommends. For most modern oils and engines, you can make changes far less often than grandpa did. Check the owner’s manual. Make sure the oil selected meets or exceeds the recommendation of the manufacturer for that engine.

To start conventional oil can go 10,000 miles under certain operating conditions also. However in some cases 4000 miles is too far for conventional or synthetic. Especially in a vehicle like a Corolla with a tiny oil sump (likely 3-4qts?). The cars you here about going 10,000 miles on synthetic typically have larger oil sumps and oil life monitors that make a more exacting estimation of oil life.

Lastly Corolla engines may be hard on oil I have no idea. Certain engines are just harder on motor oil whiles others very easy.

As an engine ages and accumulates more miles, it get harder on the oil. A brand new car could go 10,000 miles and hardly change the color of the oil, at 100,000 miles, the oil will darken in less than 5000 miles. But just getting darker does not mean that the oil is used up. Your mechanic cannot tell just by looking at it. It has to be analyzed.

I use synthetic and change every 7,500, per owners manual. The thing you must realize is that the oil itself doesn’t breakdown, but the oil becomes contaminated with the by-products found in running engines. This includes, but not limited to, unburnt gasoline, metallic particles, carbon, sulfur compounds, and a bunch of other stuff. The oil has detergents that collect and hold those contaminants in suspension. Particles large enough get caught in the oil filter. But, a bunch of stuff, like gasoline, carbon and sulfur, stay in suspension and run around throughout your engine. Changing the oil is the only way to remove this stuff.

There’s no way your mechanic can tell if the oil is bad by looking at it…unless there’s some obvious contaminate like anti-freeze in the oil.

5k with full synthetic is what I do…But I live in the North East where winter temps go below 0 frequently…and during the summer I tow a camper most weekends.

“Your mechanic cannot tell just by looking at it. It has to be analyzed.”

Since analyzing oil often can be expensive and a bother, most if us just replace the oil as recommended by the manufacturer. In addition we all tend to have the grandpa view. That is grandpa changed his oil ever 2,000 miles and did not have problems so the idea that oil will only last 2,000 miles gets past down, without noting that cars and oils are very different today.

Assuming you are not racing on the weekends, or letting your car idle for hours on end, chances are the recommendations listed in your owner's book should be fine.

“Assuming you are not racing on the weekends, or letting your car idle for hours on end, chances are the recommendations listed in your owner’s book should be fine.”

Most Owner’s Manuals offer two different change intervals, one for “normal” service, and one for “severe” operation (hot-rodding around), lots of stop & go, excessive idling, trailer pulling, etcetera.

So, even if one is “racing on the weekends” or “letting your car idle for hours on end,” just follow the recommendation for Severe Operation Service.

All car owners should take the time to read the car’s Owners Manual, particularly if any of this is a mystery. It doesn’t have to be done in one sitting and even if one just becomes familiar with the layout so that it can be used as the reference book it is, would be most helpful.


My 2006 Matrix (essentially a Corolla) manual calls for 5000 miles or 6 months,
no different interval for ‘severe service’.
Since I drive 4-5000 miles a year I change the oil every 6 months.
I don’t drive it hard or in temperature extremes so I use conventional 5W-30 oil.
This winter I’m trying 0W-30 synthetic just to see if it saves any gas.
I will still change out that synthetic oil after 6 months.

Most Owner’s Manuals offer two different change intervals, one for “normal” service, and one for “severe” operation*

  • common sense answer:

    Good point, I should have noted it.

As stated, Toyota manuals call for oil and filter changes every 5000 miles, regardless of severity of service. If you put on 6500 hard city miles, it’s quite possible to have black and “dirty” oil at that mileage. Toyota does not differentiate between synthetic and regular oil as far as the change interval goes. Neither do I, and my Toyota gets its oil changed very 5000 miles with either oil.

Under normal driving, oil change interval is mainly determined by additive depletion, and synthetics are no better in that respect than regular oils.

In short you are not being ripped off, but don’t try to save money by putting in synthetic and then stretching the interval. You are better off with a good regu;lar oil changing it at 5000, unless you live in Alaska or Minnesota and park outside.