Synthetic Oil

Is there any evidence that using synthetic oil will prolong the life of a cars’ engine ? I have just retired my 92 Geo Metro ( 225,000mi ) and purchased a 2013 Kia Rio and I would like it to last as long as possible.


I’m not sure about longer life

But it does seem to do better in extreme temperatures

And it does seem to allow for slightly longer oil change intervals, if you’re into that kind of thing

By the way, why did you retire the Metro?

Do what you are doing,seems to me like the metro gave you good service as JTG said you can go a bit longer between oil changes with the synthetic(prime reason to run synthetic is the flowability at low temps)-heat doesnt break it down as quick either-Kevin

I dunno, I had 530K on my Buick with dino oil. Kinda hard to get better than that. Oil CHANGES are more important and people who use synthetic like to go longer on the changes. On my car that requires 0-20, I use synthetic and change at 5K. On my cars that require 5 or 10-30, I use dino and change at 3K.

If the vehicle is still under warranty use the oil specified in the owners manual. If there should be an engine problem and you didn’t use the oil specified by the manufacturer it will void the warranty.

Once the vehicle goes out of warranty you can use whatever oil you want.

I consider synthetic oils to be application specific.


My educated guess is that if you’re willing to spend a certain amount – for example say $200 per year – for oil changes, you’d be better off spending it on more frequent oil changes using regular oil than less frequent using synthetic.

What did you do special to get a Geo Metro to last 22 years and 225,000 miles? Do the same with the Kia. Maintain the fluids it calls for, keep up with the maintenance, fix problems as they arise, and it will last.

As long as your owner’s manual doesn’t require synthetic, there is absolutely no evidence that synthetic oil prolongs engine life. There is an enormous body of evidence that regular oil and filter changes does.

Synthetic is required where the oil will be exposed to extreme stresses. For example, turbochargers spin up to 200,000 rpm, the units are directly in the hot exhaust stream, and the shaft bearings are lubricated with the engine’s oil. Under extreme conditions like that, synthetic is less prone to failing. But for naturally aspirated engines dino is perfectly sufficient.

I dunno, I had 530K on my Buick with dino oil.

Just one engine? Never rebuilt?

I have just retired my 92 Geo Metro ( 225,000mi )

How often did you change fluids (oil, trans, coolant)? Ever change brake fluid?

@auto-owner Correct. Original engine, never opened up except for a timing chain. Another Buick Riv at 340 same thing. Olds at 240K with no engine work except a couple valve rocker pivots for about $10.

@auto-owner, why do you doubt @Bing? I had 325,000 on my '90 Toyota, and shooting for half a million miles on the original engine, no rebuild, but an accident with a retaining wall ended that quest. The motor was sold off to continue life in another truck. I know many who have 400,000+ miles on original motors.

When it hit 500,000 I took a picture of the odometer with my old cell phone just to show. It was about 2:00 in the morning though but the electronic dash still showed up pretty good. By the time it hit 535 though I just gave the keys to the dealer and never looked back. I never want to do that again.

I dunno, I had 530K on my Buick with dino oil.

Just one engine? Never rebuilt?

Bing’s not the only one. We’ve owned several vehicles with over 300k miles. Three I kept track of after we stopped owning it. They were given to relatives…then one was sold to my daughters ex-bf. All 3 had over 400k miles…2 were approaching 500k miles (I think one went past the 500k mark). All were still on the road last I knew.

My current vehicle has over 260k miles…and runs PERFECTLY…Doesn’t burn any oil.

I don’t think so. Synthetic oil may be required for specific vehicles but I’ve never seen any proof it prolongs engine life. I’ve owned several Jeep Cherokees (not Grand) and they all went over 200K with regular maintenance. I also had 94 Ranger XLT that went 430K and is still running (different owner) and the engine/transmission were never apart. The best way to insure longevity of your power train is to make sure regular maintenance is part of it’s life. I can’t stress that strong enough.

If synthetic oil is not specified then using regular oil with dilligent maintenance will give your car long life. The exception is if you live in a severe climate, hot or cold, or do trailer towing, then synthetic oil has a distinct advantage.

Since you got 225k miles from a Metro, I’m inclined to say keep doing what you’ve done.

I will add that having analyzed a lot oils, synthetics do typically contain a better additive package. It’s not that dyno oils can’t, but most are priced so there is less room for manufacturers to include them. The higher synthetic oil prices makes the additives affordable.

And as others have mentioned, synth oils handle extremes better. They are less likely to coke at high temps, and flow more smoothly at extremely low ones.

Synthetic oils also break down more slowly, so they hold their viscosity levels closer to the original rating for a longer period of time.

All that said, if your new car is not exposed to any such extremes, and you change it often enough, the benefits of synth oils may not be worth it to you.

Given that you’ve bought a Geo and a Kia, I’m guessing you’re not a guy who likes to throw money away. Your more economical choice would be to stay with the dino oil.

OTOH, if you like knowing that in the event of some extreme happening, your car has in it the best oil, the peace of mind coming with synth oil might make it a price worth paying.

I’d probably have a half million miles on my '89 Toyota pickup by now if I hadn’t given it to my daughter. It made 338,000 with no major work before it got hit by a Hyundae. And it still wasn’t burning excess oil.