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Worth Switching to Synthetic on old Car

Is it worth switching to synthetic oil on a 1995 Buick Regal with 125,000 miles? Currently I put in the cheapest oil and cheapest filter I can find and do a change every 3,000 miles. I do the work myself so the “longer life” of a synthetic with respect to frequency of changes doesn’t matter to me. Going from 10 dollars a change to like 40 does seems a little steep. Also if I were to change do I need to do a total flush of my system to get out all the old stuff? Thanks.

What do you expect to accomplish by using synthetic oil?
Longer engine life? That’s not very likely even if you had used synthetic from the beginning, let alone after 125K miles of wear have gone by.

You can switch and mix conventional with synthetic as much as you want. There’s no need to flush anything.

Nope, keep doing what you’re doing.

Sounds like you have a good plan already. Synthetic oil will not offer your engine any benefit at all.

You’re doing an excellnt job maintaining the car with 3,000 mile oil and filter changes, better than the required. Switching to synthetic will yield absolutely zero benefit to you.

And if you ultimately do decide to change, you’ll not need to flush the engine. Dino and synthetic oils are totally and completely blendable and mixable. They’re both chemically exactly the same, except that synthstic has more consistant molecuular size and contains fewer impurities. has a good primer on oils. I recommend a visit.

Thanks for the site it looks really good. I was reading which is what got me thinking of switching.

Switching would give you a little less wear and a little better mileage, but the differences would be very small.

You’re doing an excellnt job maintaining the car with 3,000 mile oil and filter changes, better than the required. Switching to synthetic will yield absolutely zero benefit to you.

Unless he uses it for enough miles to cover the added costs. There are a ton of would be tight wads that think they’re cheap with conventional oil doing short OCI’s. They’re actually costing themselves money and time more often than not.

Unless you’re retired and your principle activity behind the wheel is heading down to the local McDonald’s for the “coffee” (multi)hour …anyone should be able to get 6months out of most oils today. If it takes a synthetic to give you the confidence to do so, then so be it.

I know a lot of people say you can go longer with an oil change I just like to stick with the factory service schedule. I figure that when they wrote it they had dino oils in mind and there was a reason for changing every 3000 miles. What changed so that oil changes are needed less frequently. Has dino oil really gotten that much better?

Oils have gotten better (better dirt suspension, longer-lived viscosity modifiers) and engines have gotten cleaner (no lead, better tolerances, less blow-by). So 3000 miles is now appropriate for hard usage, but 5000 or more can be appropriate for less extreme use. Of course, you’ll find lots of 3000 mile fans. I fine with 5000 miles.

You’re doing fine; keep it up! Unless you live in Alaska or in Minnesota and park your car outside in the winter, synthetic will get you no real benefits.

A 1995 car is 15 years old and you must be putting on less than 10,000 miles (8,333 & 4 trips per day) a year or about 5.7 miles per trip; that’s “severe” service and the 3000 miles oil and filter change is exactly right.

Happy motoring!

I still see misconceptions about synthetic oils. There is no such thing as magic oil. If there was any truth to less wear with a synthetic, to any SIGNIFICANT degree, then commercial fleets would be all over it. Fleet operators that use synthetic have the same overhaul rates as conventional users. The distinction is in the amount of down time they experience.

The viscosity index of most modern oils is not that out of whack between conventional and synthetic.

Formula Shell 5w-30 conventional VI: 153
Formula Shell 5w-30 Synblend VI: 158
Pennzoil Platinum 5w-30 synthetic VI: 169

Not a biggie in my opinion. Cold flow properties at sensible temps is not that big of a deal and they’re all within limits under the 5w spec’s for the Cold Crank Simulator and Mini Rotary Viscometer for TRULY SEVERE cold.

In general, outside of some turbo spec (add all niche spec’s) the sensibility of a synthetic is all about $$/mile. If you’re in a common service in a bread and butter application, you need to get more mileage out of synth …and that’s about it.

Even your fancy Euro alloys that spec high $$ synthetic 5w-40 or 0w-40 fall under that same fundamental rule. You can surely use a 15w-40 in those same engines without any wear aspect ever getting into the picture. You just can’t do it under the multiple axis of requirements. It can’t last as long …with so much fuel economy …with so much deposit control …with such and such wear. Remove any of the complex “corridor narrowing” requirements and lots of oil works.

So, use a synthetic ONLY if you’re going to get your money’s worth out of it. It’s usually just that simple. There is no magic oil.

My intent was to suggest that since he’s regularly changing his oil, even more often than needed, synthetic is unneccessary. But I agree that if it helps him sleep better than he should use synthetic. The engine might not last longer, but if he sleeps better his cardiovascular system just may.

I’m a tightwad to the point of being proud to be cheap. But I’d never extend and oil change and since I’ve never worn out an engine using dino I’d never spend the extra money for synthetic. But, then, I’d never buy a turbocharged engine either…

Zero value. Stick with your current regiment.