Grant1424

Hello everyone,

I have an original Rocket 350 in a 1972 Cutlass. I am getting ready to do an oil change and I wanted to know what are the thoughts and input of using Synthetic oil. Is this better for the older muscle cars or can this cause any issues?

MDchanic

Synthetic may cause new oil leaks you never imagined you had.

- Eric

brddg

Synthetic is awesome. In the right conditions. If your engine doesn't leak or smoke or use oil (all important). The synthetic oil will last longer, protect better, and be cheaper in the long run because the higher initial cost is far offset by the extended mileage change. However, if your engine uses oil now it will use more synthetic because the oil molecules are smaller. The same reason if it leaks it will leak more. If you have a new engine and put synthetic in it, it will never break in. The rings won't seat because the oil works too good. It is an awesome product if introduced the after break-in period and will extend engine life by a lot. Don't use on a worn-out engine though. Hope that helps.

brddg

BTW. You may be shocked by the synthetic difference in the tranny and axle if you add it. Temperatures in these drop by quite a bit by doing nothing other than changing the oil.

Sugar Bear

Petroleum based non-synthetic, diesel rated "C" type oils supposedly have excellent detergent packages and higher levels of zinc. Zinc is supposed to be good for flat tappet camshafts which is the case with your engine. In a warm climate, I'd be using one of the major oil company 15w-40 petroleum based diesel rated oils, with a very high quality filter.

Change it often and when the oil is warm, just be careful not to get burned. Changing the oil warm gets some of the contaminants/sludge held in the oil and the warm thinner oil flows out better.

X2 on MDchanic and brddg concerns about additional leaks. About the extended changes on synthetic oil, even if the oil maintains an excellent ability to lubricate, cool and cushion, where do the contaminants go? FWIW, I'd rather stay with petroleum based oil in an older street motor and change it more often.

Allan R

New conventional oil is not the way to go. It doesn't have enough zinc. Not opening that can of worms here, but DON'T use synthetic in your stock 350 with higher mileage.

I'd suggest some Valvoline VR1 or similar as it has the right high zinc formulation for flat tappets. Costs a bit more, but worth it.

RandyS

Wally World sells Shell Rotella 15w-40, 4 qts. for $12.97. Can't beat that!

OLD SKL 69

I agree. Don't use conventional oil unless you add zddp (zinc additive) to it. The Valvoline already has it in there as Allan said.

Koda

Many new cars come with only synthetic ever having been in the engine, with the Chevrolet Corvette a notable example. However, that could be also a roller cam thing vs flat tappet.

Grant1424

Thanks everyone!! I am going with the Valvoline VR1.

L69 equipped

1999 Silverado Z71 5.3.

Synthetic (usually just Wal Mart branded 5W 30) since new.

400,000 miles and counting and engine has NEVER been worked on with the exception of routine maintenance (plugs , hoses , etc.).

No leaks whatsoever and still has 60 PSI at 1,800 RPM's, 40PSI at idle.

I beleive that should speak for itself.


Dave

oldcutlass

I also use VR1, it's in the top 5 conventional oils with the proper levels of ZDDP. There have been a lot of discussions in recent years documented on here about motor oils.

Those using the diesel oils need to do some research on the changes that have taken place in formulation due to the onset of diesel emission controls and possibly reevaluate it's use.

MDchanic

It does, but the sealing materials and designs, and the overall history and age of your engine are not the same as those of an original Olds engine from over forty years ago.

Nobody said that a 1999 engine would leak if you used synthetic oil, only that an Olds engine from the '60s or '70s, with 40+ year old seals, that has used conventional oils all its life, and probably spent a few years here and there just sitting, would.

By the way, I have a 2000 Jeep with a helluva lot of miles on it, which has had synthetic oil its whole life.
Barely leaked a drop until it rusted a hole in its oil pan (first oil pan I've ever seen that rusted through, because it was the first one I've ever seen that had no coating of leaked oil residue on it).

- Eric

L69 equipped

I have never seen a rusted through oil pan. That seems like my kind of luck though.

I have never used any of the synthetic in either the 66 olds or my 64 riv.

The main reason is (as was mentioned earlier about the molecular makeup of synthetic). I also don't really put that many miles on either of those cars so oil consumption is not really an issue.

The olds doesn't leak or use a drop of oil, EVER.

The buick (425 nailhead) by design, uses oil and because of the inadequate valve design, actually creates blowby (even pops the dipstick) when I "blow the carbon out". But I don't mind cleaning it up. There is just no other feeling like making a 4,200 lb. lead sled cruiser roast the tires and slide sideways !

Gotta love the 465 lbs. of torque.

But truth be told, the sound of the olds tri carbs opening in harmony as you run through all 4 gears is music to my ears as well.

The BOP family is a special one indeed.


Dave