Switching motor oil from synthetic to conventional

[JPsLC]

I bought a 1998 Landcruiser last month with 215,000 miles. The previous owner switched to synthetic oil (Pennzoil Ultra Platinum Full Synthetic Motor Oil) in the motor somewhere around 150,000 miles, and I'm wondering if I need to stick with a synthetic oil. I prefer Valvoline, and while researching their products I read through their FAQs.

Question 4 has me scratching my head: Is it ok to switch back and forth between regular and synthetic motor oil? I heard this causes leaks? Is this true?
Switching between synthetic and conventional oil does not cause problems. Because the oils are compatible, you can switch back and forth as often as you like.

I've always heard switching from synthetic to conventional would cause the oil to foam, but it appears that claim is either outdated or unsubstantiated. Does anyone with experience have any opinions on the matter?

PS - There are plenty of threads discussing the pros/cons of synthetics versus conventional, and I'm not looking to have that conversation here.

 

[huntsonora]

First of all, if it isn't broke, don't fix it. Secondly, Pennzoil Ultra Platinum is a FANTASTIC motor oil. I would stay with the PUP

I run PUP 5w-30 in my 2006 Tundra with the 4.7 V8 (2UZ-FE) and it is noticeably quieter than it was with Mobil 1. PUP keeps your engine clean and is damn sure tough to beat

 

[Stumpalump]

I bought a 1998 Landcruiser last month with 215,000 miles. The previous owner switched to synthetic oil (Pennzoil Ultra Platinum Full Synthetic Motor Oil) in the motor somewhere around 150,000 miles, and I'm wondering if I need to stick with a synthetic oil. I prefer Valvoline, and while researching their products I read through their FAQs.

Question 4 has me scratching my head: Is it ok to switch back and forth between regular and synthetic motor oil? I heard this causes leaks? Is this true?
Switching between synthetic and conventional oil does not cause problems. Because the oils are compatible, you can switch back and forth as often as you like.

I've always heard switching from synthetic to conventional would cause the oil to foam, but it appears that claim is either outdated or unsubstantiated. Does anyone with experience have any opinions on the matter?

PS - There are plenty of threads discussing the pros/cons of synthetics versus conventional, and I'm not looking to have that conversation here.

The FAQ from the oil company clearly answered your question yet you start a Ford vs Chevy thread and ask us not to have a conversation. Do you still use bias ply tires?

 

[JPsLC]

Not really Stump, I've just always heard it was a bad idea and thought I shouldn't believe everything I read on the Internet. I'm simply asking if anyone had experience with switching.

Huntsonora makes a good argument for not making a problem, and I appreciate his feedback for which oil has served him better.

 

[toyotech]

You can switch. It may just smoke a little bit but will stop.
Heard the additives from synthetic will burn off when switching back to conventional. But you can switch back if you want.


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[rayra]

The FAQ from the oil company clearly answered your question yet you start a Ford vs Chevy thread and ask us not to have a conversation. Do you still use bias ply tires?

... with nitrogen in them?

(figure we might as well get all the hokem in one topic)


Switching is fine, enjoy the wallet relief.

 

[1911]

Question 4 has me scratching my head: Is it ok to switch back and forth between regular and synthetic motor oil? I heard this causes leaks? Is this true?
Switching between synthetic and conventional oil does not cause problems. Because the oils are compatible, you can switch back and forth as often as you like.

I've always heard switching from synthetic to conventional would cause the oil to foam, but it appears that claim is either outdated or unsubstantiated. Does anyone with experience have any opinions on the matter?

Old wive's tale. All modern synthetics are perfectly compatible with conventional oils.

 

[DaveInDenver]

Complete bull. I ran Castrol Syntec in my truck for a bunch of years right after buying it with 100,000 miles on it. The timing chain let loose at about 175,000 and I rebuilt it. I drove it the next 15,000 mile with conventional GTX, switched to Syntec again at about 205,000.

I decided it wasn't worth putting expensive oil in it anymore at 235,000 and went back to GTX and now at 267,000 the Blackstone oil analysis doesn't indicate one bit of issue. It's never foamed, it's never leaked (other than my rear main seal, which it started doing long ago because I screwed it up during the rebuild), it's never had anything but the same oil pressure. I do periodic valve lash adjustment and the cams and followers look the same, no evidence of anything different.

The only caveat I'd suggest is that it's generally best to stick with a brand of oil and that's because additives can interact between brands. So if you use Pennzoil, use their conventional or synthetic, don't switch to Quaker State or Castrol and mix and match. I'll also say do oil analysis to figure out intervals. My engine doesn't wear out oil as such but it gets contaminated. So it was pointless to run synthetic because the oil was getting full of combustion byproducts before the base oil was ready for replacement. So I stick with 3K intervals with GTX.

 

[Scoutn79]

Here is what I have heard regarding switching oils.
This is for going from conventional to synthetic on a high mileage motor.
Since the synthetic oil leaves less deposits and is highly detergent it will loosen sludge in the motor and could clog your oil filter as well as cleaning deposits from around old seals that could be marginal in their ability to keep oil in..Thus you get leaks this way not from going from synthetic to conventional.

Darrell

 

[DaveInDenver]

That's Internet lore.

I switched back and forth a few times and nothing that wasn't already leaking started new and nothing that was leaking stopped when I went back to conventional. If your engine seals leak, the problem is the seals are bad. Stopping the leak with poor quality oil that sludges is doing no good for the wear points either, so fix the seals and run decent oil.

The story goes way back to when synthetic did actually cause rubber seals to shrink (or well more properly /not/ swell, which is what oil used to make seals do). But that was decades ago and (1) seal materials are different now and (b) oil formulations are different. It's just not true anymore. Conventional oils are tons better than they used to be, as well, so it's less likely to be as drastic of a change between the two.

I will admit that in your Scout it may still be true if you're still running very old (original) seals. But the seals in my engine are all less than 10 years old generally.

 

[Buliwyf]

You can switch back and forth at will.

As Scout mentioned. Synthetic is better at cleaning, and is thinner. It'll leak out of marginal seals. That's not the oils fault, it's the engines. Change conventional every 3000, synth every 5000-10000.

 

[toyotech]

Sludge only builds up from lack of oil changes. Your engine should be clean and have no sludge anywhere.

Your oil passages will get plugged up from said sludge and have bigger issues than a leak
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[JPsLC]

Thanks for all the feedback! Now I can finally do an oil change.

 

[Fargo]

I've switched back and forth in my car all the time with no issues. I like to run full synthetic in the winter and conventional in the summer. The only thing I do not run is synthetic blends. That is because you have no idea what you are paying for. How much is synthetic and how much is conventional? There is no regulation on it and no one states what the blend is. It could be 50/50 or it could be 90/10. You have no idea. Yet you assume its about 50/50 because the price is halfway between full syn and regular. Besides, I don't really see a need for synthetic blends.

I have heard that switching between brands is bad too because of the differences in detergents but I have done that too. So far I have not had issues. I imagine that is folk lore as well. I would think that the majority of the detergents drain out with the old oil. At least after a couple changes they should be drained out. I would also suspect that the detergents the oil companies use are very similar if not the same. Probably just different quantities of each. But this just me guessing. They might formulate complete different detergents, but I can;t imagine they stick around the engine that long. But if they do what issue are they causing? Are they causing sludge or are they doing a super cleaning and people are getting leaks like they used to blame on synthetic???? My wife washers dishes with different detergents in the dishwasher from time to time too. Never had a problem there either. AT least not with the switching. Sometims some detergents are just bad.

 

[joejeep92]

It won't hurt a thing to switch back and forth. I love the synthetic oils, more consistent size on the molecular level gives better lubricity as well as the additive packages aid in cleaning. My Tundra has almost 100k on it and the oil drains out after 5k looking brand new.