GTO1966

For an old C3 with 90k on it I wanted to use Castrol high mileage semi syn 10/30.....Ive read some times synthetics will leak when convential would not have. Whats your take on synthetic in older engines?

CV62Air

Lots of good info in the two oil stickies above! I don't drive mine a whole lot(only put about 1500 miles on it in almost 4 yrs), but have been using Amsoil ZROD in my annual oil change!!

In other vehicles I have used many different oils, but mostly Mobil1 or Amsoil synthetics and have never have any problems with leaks.

OldCarBum

I had a Harley I restored for show and the service tech talked me into running a synthetic when I reassembled the bike. I did and had oil seeping between the engine casings. It wasn't dripping, I just got nasty oils smears on the abutting chrome parts. I talked to another tech who told me that the older castings and gasket materials would allow the synthetic oils to seep. I changed back to non synthetic and the seeping stopped immediately and I never had another issue. I've had several show bikes and hot rods that I drove under 1,000 miles a year but changed the oil every three to four months and can't justify the cost of the synthetic over the non synthetic oils. I run synthetics in my Chevy truck and Acura because it is recommended, and it's been trouble free.

rcread

I tried synthetic when I first got my '71 21 years ago. The heads had worn valve guides and the car would barely run because of the oil leaking into the combustion chamber. If there is a weak area in your system, synthetic wil find it. I built a new engine for the car, and now that it's broken in, I'm going synthetic for my next oil change.

cv67

90 k mi who cars really thats a lot of mi espt wihtout an OD
Run what you want and run er good
If its worn youll know and go through it
The internet is FOS far as opinions go most what to sell you something
If I can help pm me

7T1vette

Considering ONLY the primary purpose for the oil....lubrication...there is absolutely no question that full synthetic oil is leaps-&-bounds better than organic oil. Moving parts wear at a considerably slower rate with synthetic and friction is greatly reduced.

Leakage is not really a function of the oil type...it is a function of how well sealed is the engine. If you have worn seals, synthetic oil will leak more than organic oil: the molecular size of syn oil is smaller, so it is easier to flow thru the same size hole!

Syn oil is BEST for your engine and working parts. But you may need to fix your old/worn seals & gaskets if you want it to be 'leak free'.

jb78L-82

Absolutely correct..Synthetic oil is superior to conventional oil, period.....If you have leaks using synthetic oil, your gaskets are junk....not that you should not use synthetic oil...fix your gaskets...the bubba method is to use conventional oil to band aid the issue.

ddawson

Synthetic as long as it doesn't find a way to leak or find it's way into the combustion chamber.

7t9l82

Yes! That's the answer to your question. If you have a gasket or seal that's bad then it would possibly leak, but you were getting ready to have a leak anyway.synthetics are superior in every way.

Chinaski

I use dead dinosaurs, as I am doing everything in my power to increase my carbon footprint.

7T1vette

Good for you! You should be so proud...

63mako

Amsoil Z-Rod 10W-30 is a perfect oil for these cars. It has 1300 PPM ZDDP, Seal swellers and conditioners, Antioxidents, Corrosion inhibitors and is a Group IV base stock true synthetic. It even ranks high on the film strength testing 540Rat is doing.

myoriginal77

Don't ...

Capt. Shark

It's what I use

fishslayer143

synthetics are FAR SUPERIOR in every way to dino oils.. and contrary to old wives tales, they do not cause leaks.. bads seals leak .. seals are cheap, if one leaks, replace it.. your motor will thank you with a much longer life

Ydnar44

Oil is as natural as water, people seem to forget that,

68notray

I drive my car about 200 miles a year so it don't make much of a different what is in the pan. Just so you know thought, I run the Valvoline VR which has the zddp

7T1vette

Before oil was discovered, folks used whale oil or bear grease to lube their stuff. That sounds like your 'fall-back' option.

Organic oil has served us VERY well for nearly 200 years; and it will be serving us yet in the future...until it is gone. Then, we'll be back to whale oil and bear grease.

Let's use it up FASTER so we can get there sooner.

cagotzmann

This oil Brand made my factory L48 Engine run so quiet, valve tapping noise was so quiet compared to Mobil 1 15W 50 Brand.

Flows excellent for cold start up, great wear protection for these older engines. It didn't add much in oil leaks for me.

7T1vette

Valvoline full synthetic works for me. $23 for 5 quart bottle at Wal-Mart. I have the 'base' engine; if I had solid lifters/strong valve springs, I would probably go the Amsoil route, too.