Is all oil the same?

I always use synthetic oil in my car, is it worth while, since I dont drive my car hard at all. I keep it till it has 100k miles or so…just wondering if the extra expense makes sense?

Synthetic is great oil, but if you only keep cars to the 100K mark, why bother? With regular service they’d make it that far on dyno juice. The NEXT owner is the one who will benefit.

Full synthetic motor oil has much different properties than conventional motor oil. But, the question of ‘Is it worth it?’ requires much more information than the two sentences offered.

BTW, there are different types of synthetic oils on the market. A full-synthetic oil is manufactured from a synthetic oil base. Mobil One and Castrol Syntec are both considered full-synthetics. These oils have an oil weight band that is 98% of the desired oil weight. Semi-synthetics are manufactured from conventional base oil, but use synthetic manufacturing methods. They are better than conventional oil, but don’t offer the same properties of a full-synthetic. They have an oil weight band of 90% or better. Then, there are the synthetic blends, which are synthetic and conventional oil mixed together. These have an oil weight band of 82% or better. Finally, the conventional oil has a weight band of 70% of the desired oil weight.

The reason this is important is longevity of the oil. The higher a percentage of the oil within the desired oil band, the longer the oil will provide wear protection before requiring a change. The change is required when the oil collects enough contamination to change it’s weight properties out of the desired weight band. If 98% of the oil is the desired weight band, it takes a lot more contamination to affect it.

To answer the question of ‘Is it worth it?’, consider your driving habits. If the car is a daily driver, and you change the oil every 3-5 thousand miles, which is every 2-3 months, your wasting your money on synthetic. Conventional oil does this job very well.

If your car sits for long period of time, and it takes up to a year to reach 5 thousand miles, synthetic oil will provide much better protection from the 5th month to the year between oil changes over conventional oil.

If your car is a seasonal car, like you use it at a vacation home or just for the summer, conventional oil is fine. Just change it at the beginning of the driving season and the end, before you park it for a long rest.

If your a real road warrior, and travel quite a bit by highway on a weekly or monthly basis, like adding 30,000 miles a year or more to your car, this is the situation synthetic oil was created for. Driver’s like these can go up to 15,000 miles or more between oil changes with synthetic, where conventional oils need changing at 7,500 miles.

Also, today’s cars can easily hit 100,000 miles without problems due to better manufacturing methods, tighter tolerances, and better materials over the older cars from the 80’s and earlier. I generally keep a car or truck well past 200,000 miles. With proper maintenance, they can last much longer. Hope this helps.

As long as the oil meets the specification of the car’s manufacturer for that car, it is fine. Some cars need synthetic some don’t. It should have that information in the owner’s manual. Some cars will have problems unless synthetic is used, even at 100,000 miles unless you only want to get to 100,100 miles.

Very true Joe. Good point. The OP didn’t say what kind of car s/he has.

Joseph said it perfectly.

I keep my cars for (in some cases) hundreds of thousands of miles. In over 40 yrars I’ve never worn an engine out and only used dino oil.

Any properly designed and manufactured engine that’s treated and maintained per the manufacturer’s recommendations will last the life of the car. Engine longevity starts with proper selection, which is the result of good pre-buying research and a bit of luck. has a good primer on oils. I recommend a visit.

I don’t know if you’ll see any benefit if you only keep your cars 100K miles. (though the next owner will)

I do know that I had my leaky valve cover gaskets replaced yesterday and after over 240,000 miles, most of it on synthetic oil, there was NO sludge to be found under either valve cover! Not bad for a 15-year old engine. I use Mobil-1 and go 6,000 miles between oil changes. In that time my car uses about ? quart of oil, where it used to use 1-2 quarts between 3,000 mile oil changes.

Personally I won’t use anything but synthetic any more.

Everyone is entitled to do as they want with this issue but I do have two questions.

  1. What do you think is the reason (what qualities does synthetic have) that caused such a drop in oil consumption?

  2. What properties does synthetic oil have that prevented sludge build up under the valve cover? Are you attributing the absence of sludge solely to the use of synthetic oil?

Our still somewhat new 08 GM car requires synthetic oil for the 100,000 mile warranty to be retained. That makes it possible that synthetic may have something over dino oil. Otherwise why would GM bother to require their vehicle buyers to use a more expensive oil? They are concerned with operating costs as they did, after all, design the engine to use 87 octane gasoline.

Toyota engines a while back had a sludge problem. One common suggestion on car boards is to use synthetic oils. The reason synthetic resists sludge is it has much more heat tolerance. I do not think it is rational to say there is no difference.

If there were no difference, race cars would not use synthetics.

The mistake I see you making is worrying about what others think. If you like synthetics, that is a valid choice, don’t worry if others have a different viewpoint. Over the life of the car, or the time you choose to drive it anyway, the difference in cost is nothing compared to purchase price. And, on some models, that are sludge prone, you odds go down of problems. Cheap insurance. Do not ever apologize for over maintaining an expensive vehicle.

That was a two part question, Part 1 was why did synthetic oil reduce the oil consumption?

With oil the most important thing is using one that meets your vehicle’s required spec/grade and changed on time for your driving type. That is 90-95% of the contribution to your engine’s life. Whether it is X brand or synthetic(over conventional) is 5-10% of the equation.

I will add a very important thing is checking engine oil level every 3-4 fuel fillups. Low oil level is very hard the remaining oil as you make it all work much harder.

I have a Toyota with the sludge-prone engine. It has 143K miles on it. The oil was changed every 5K with only dyno oil. (Note Toyota dropped their oil change interval from 7.5K to 5K once they admitted the sludge problem.)

My engine has no sign of sludge. I agree it’s only a ‘1 sample’ data point, but it is exactly how Toyota recommended to service the vehicle.

While I agree that synthetic does lower the odds of sludge (especially in a sludge prone engine), there are still many cases where dyno oil works just as well.

It depends on what you drive. If your owner’s manual recommends or requires synthetic oil, use it. Otherwise, it isn’t worth the added expense.

My mother’s 2002 Toyota Sienna also has one of the “sludge-prone” engines. It gets a diet of regular dino oil every 5,000 miles and hasn’t had any sludge problems either. When my mother first got this vehicle, I told her about Toyota’s sludge problems with their V6 engines. We agreed to shorten the oil change interval to 5,000 miles and keep a close eye on it.

Our still somewhat new 08 GM car requires synthetic oil for the 100,000 mile warranty to be retained. That makes it possible that synthetic may have something over dino oil. Otherwise why would GM bother to require their vehicle buyers to use a more expensive oil?

There are several possible reasons GM might require synthetic oil:

  1. GM might be getting a kick-back from oil producers who want to sell more high-profit synthetic oil and less low-profit conventional oil.

  2. GM thinks its Dex-Cool long-life coolant is such a good idea that they want to apply the same concept to oil.

  3. GM thinks that requiring synthetic oil will make you think your new car is more high-tech than it really is. This kind of thing is what marketers call “perceived value.” I can hear it now, where some teenager is saying to his friend “it must be a better car because it requires synthetic oil.”

  4. GM wants to extend service intervals so that maintenance isn’t such an inconvenience.

The fact that GM requires synthetic oil doesn’t, on its own, indicate the superiority of synthetic oil in applications for which it was not designed or mandated. All it means is that if you want to keep your warranty, you better use it. Just like Dex-Cool coolant, it isn’t necessarily superior.

If you consider the Dex-Cool class action law suit, perhaps you will be better off switching coolants and oils as soon as the warranty expires…that is if you want your GM vehicle to last.

Really, GM has made so many boneheaded moves in the past, I discourage you from reading too much into any decision they make.

I wasn’t expecting a pop quiz, but I’ll answer your questions to the best of my ability:

First off, I watched the oil consumption drop with the change to synthetic, and I’ve seen the same effect with my truck as well, and my gf’s SUV, so in my mind it has been established that (at least these three) vehicles fare better with synthetic.

Synthetic oil, having a higher flash point and much better stability tends to decompose less at operating temperatures—this also partially accounts for the lack of sludge, as the oil isn’t breaking down and leaving a tarry residue. I wouldn’t attribute the engine’s cleanliness entirely to the synthetic oil, but I would say that the combination of regular oil changes and synthetic oil have kept it very clean. And while I didn’t set out to do an experiment with another identical car using dino oil as a control, I am personally convinced (admittedly just one man’s opinion) that my engine would not be as clean if I had been using dino oil for the last 150,000 miles or so.

In other news, I don’t drink cheap beer either, and I use alkaline batteries in my smoke detectors.

A question was asked…what kind of car do I drive. I have a 2006 Cadillac DeVille with the Northstar engine and a 2008 Buick Enclave. I started using synthetic oil back in the 70s because I knew about their ability not to thicken up in lower temperatures (in Wisconsin it gets cold). It is not a question of money, just wondering what everyone thinks about the logic in using these more expensive oils. I know gas turbines (jet engines) have used synthetic oil for decades because of the superior lubrication properties. I assume I am ensuring the next owner of my cars will get a good engine since I use premium filters too…such as mobil 1, purolator pure one, and delco ac, and no…I dont use fram, none of them. Anyway, thanks for your replies.