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Registered
2001 Camry
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498 Posts
Discussion Starter #1
Hi TN - hoping someone can give me a clear explanation here. Did a lot of googling but I'm still a little confused.

My Camry with 145K is leaking just a little bit of oil. I bought it 3 years ago with 131K, but I think conventional oil was always used on it. Since I had always used Mobil 1 High-Mileage Full Synthetic on my other 2001 Camry, I started using the same on the “new” Camry. I knew at the time that using synthetic oil in an older engine that hadn't been using synthetic oil could cause leaks to appear, but I didn't notice any problems with oil leaking until a few months ago.

This is what I don't understand: How is synthetic oil of the same weight/rating (5W-30) any "thinner" than conventional oil of the same weight? If the oil was truly thinner/lower viscosity, shouldn't it have a lower weight? Eric the car guy had the best explanation I could find, where he considered the "viscosity" to be attributed to the weight and "flow rate" to be attributed to conventional vs synthetic, but that didn't make a whole lot of sense to me since isn't the flow rate based on the viscosity?

So, I'm going to stop using Full Synthetic 5W-30 with my next oil change. But, what difference does it make if I switch to conventional 5W-30 (same weight, but conventional oil) or switch to a higher-viscosity Full Synthetic like 5W-40, 10W-30, or 10W-40?

Any input is appreciated. Thanks!
 

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Super Moderator
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12,871 Posts
As you've found online, you're gonna get conflicting opinions and read a lot of anecdotal experiences with this. So it's probably best just to try it and see for yourself. It's quite likely your motor simply developed a leaky seal somewhere. It happens.

"Screws fall out all the time. The world's an imperfect place."
-Bender

 

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Registered
2013 Subaru BRZ
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1,809 Posts
M1 HM full synthetic oil, honestly, is cheaper than conventional if you buy them with rebate/promo. So if the engine does not use too much oil, I won't bother to switch. Just let it burn and add once between OCI.
 

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short-throw dipstick
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5,969 Posts
Look into ATP-205. I have had good results with minute, irksome leaks.
I read a couple reports of ATP-205 stripping oil pan paint, and then the flakes clogged up the pickup screen. Not sure how common that is across different oil pans on different engines. My local NAPA had only one of their leak stop-in-a-bottle products that flew off the shelf, CD2 (made by Turtlewax). Every local who used it swore it was magic. For some reason, Turtlewax took it off the market.

This is an interesting situation to be sure. Whatever you do, I'll +1 using a high-mileage variant of any oil you choose, so the seal swellers will help you out. I don't try leak-stops myself, whenever a customer wants be to deal with an oil leak I fix all leaks, then start them running a high-mileage full synthetic from then until time stops. The ones who don't want to spend money fixing leaks, I tell them oil is cheap, even if resealing isn't.

My gut feeling says the only real change will be shorter OCIs, but then again, I've never swapped something from running synthetic for a long time to conventional.
 

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Artistwifey
99 Camry
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24 Posts
Well, I have 311,500 on 99 Camry le 4cyl.- 297,000 when the car was given to us.CEL on since that time. BUT, no idle issues. All new belts. New engine oil seal @ 307,000.
Use 5w-30 full synthetic, not high mileage type. At the new oil seal time till 310,000 oil would go down 1/2 quart plus a month (every 1,500 miles)
Added tc-3w, 4oz for every 5gallons of gas- and this month, 1,500 miles so far on the oil+ filter change, there is absolutely no oil leaking. Hubby says the clean Ashless burn
Has made the difference.....
Whatever the case and codes, the car runs smooth and for 14,000 miles with a CEL.
Go figure.
I’m happy for now.
Your situation with your Camry is interesting.
 

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Registered
93 Camry, 98 Camry,
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678 Posts
^^^^^ TCW-3 You should only add 1 oz to every 5 gallons of gas although adding that much acts as an octane booster. I have run it in my car for 8 years now. You really should get the CEL checked out. I have been told the reason synthetic oil seeps through old gaskets is because the oil particles are all uniform, whereas conventional oil has different sized oil molecules which keep it from leaking and the lubrication is not as efficient because of that. Conventional is fine as long as you do normal oil changes.
 

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96 Toyota Camry
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28 Posts
I'm a cheapskate, and my Camry's have always leaked, so I use whatever's on sale - conventional or synthetic. You can go back or forth. I have noticed lately that generic synthetic oil is getting cheaper everyday! But for the last 3 years, Pennzoil has had the below deal going, limit 2. If you need more, have a friend buy you some.:deal::deal:

AMAZON PENNZOIL SYNTHETIC OIL REBATE DEAL, 5qt. jug $12.68 after rebate, free shipping > $25 available:
[ame]https://www.amazon.com/gp/product/B01MF97JE5/ref=ox_sc_saved_title_7?smid=ATVPDKIKX0DER&psc=1[/ame]

- The rebate is good at many retailers, including walmart, and for many different weights of Pennzoil synthetic. See the form.
 

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イリジウム
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11,872 Posts
You can look up on the technical data sheet and find out the CSt at 40 (cold) and 100 degrees C. Mobil-1 tends to be on the thinner side, as are Pennzoil Platinums that use Gas-to-Liquid synthesis.

Some complained PP in Toyotas there are more valvetrain noise. Haven’t noticed it myself, it ran well.

High mileage oils are thicker in the range and therefore you won’t see the “energy conserving” wording on them.

You can try high mileage version of synthetic and see. Gen 4s are sludge monsters, so synthetics will help.

But seal conditioners can only do so much, at some point you’ll have to reseal.
 

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Registered
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2,964 Posts
I would first try a higher viscosity Mobil 1 High Mileage oil before giving up on synthetic. If you want to go back to conventional, make certain it is a High Mileage formula, otherwise the seals may start leaking worse than before (assuming your seals/gaskets are leaking).
 

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Moderator
2015 4 Runner SR5
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3,709 Posts
This is what I don't understand: How is synthetic oil of the same weight/rating (5W-30) any "thinner" than conventional oil of the same weight?

From HowStuffWorks:


"The main difference between synthetic motor oil and conventional motor oil is found in their molecular structure. In a mineral oil, the molecules come from organic, natural materials, and as we know, nature isn't always consistent. There can sometimes be a few oddball molecules in mineral oils. Synthetic oils, on the other hand, were created by scientists in a lab. The molecules are uniform, and they line up like good soldiers inside of your engine."


I have heard some say the synthetics manage to get through smaller openings in the engine due to the molecule sizes being uniform and smaller. I dunno. You can up to a 5-30 full synth to see if it helps, and use high mileage blends as was mentioned. But the engine will consume oil, and that consumption will increase over time. A rebuild of the pistons and valves helps.
 
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