johnven

I have always put regular oil from the dealer on my 86. As most 86's the gaskets seem to seep a little and I've had the gaskets changed and tighten them down every so often. Is it OK or a good idea to change to a synthetic oil after 31,000 miles and 25 yrs?? Due for a change and I use synthetic in all my other cars, but I did this since new.

Will the small seepage on the Valve Covers be worse or not? Due to tighten them down, just dab of seepage.

Dumb question, I change it every season even if only a 1,000 miles a year, is there a calender time period oil goes bad?

for some reason I thought if you broke in the engine on regular oil you should continue to use it and also thought small leaks would be worst with synthetic. Please any comments would help.

Also if you could say which synthetic you like, I use mobil one in the other cars.


Thanks

BADDUCK

In your 1986 GM recommended regular oil. I would not change after all this time. You won't notice a difference and it costs more. Oil will not "go bad" from sitting over a season or two so don't worry about that. Hopefully you at least run your car every few weeks,

c4zf6nut

I use GM 10W40 SL rated (and ACEA A3) semi synthetic blend oil in my 89 COrvette, and in the hot days of summer in traffic, oil pressure is too low for my comfort, and my car has 30,000 easy miles....

My car has roller tappets, yours have flat tappets so it is important for you to use oil with extreme pressure additives, like ZDDP, this rules out many Mobil 1 products except 15W50. Just look at the test results below.

10W40 Maxlife and Durablend are the only semi synthetic which is ACEA A3 rated oil on the market, Maxlife also happens to have seal conditioners. 10W40 can be used down to -20F, and should be much better at colder temperatures. Mobil 1 is made from Group III base stock, not really full synthetic chemistry so synthetic vs non synthetic are more marketing terms. Stick to standards like ACEA A3. Only the best oils will have ACEA A3 certification, only a few grades of Mobil 1 are advertised to satisfy the spec just like Valvoline Maxlife 10W30 or 5W30 do not satisfy ACEA A3.

If you want to an oil which will not leak Maxlife 10W40 would be a good choice. This is the oil grade of choice for most cars in Europe and none comes SM rated, all the oil is SL rated (older spec).

Even Mobil S syntetic blend (available as factory fill in Europe for our Opel with the Ecotec engine, also used in Chevrolet Aveo in the US, guess what oil they use in the US for the same engine) 10W40 is superior to Mobil 1 in wear tests. There are some good synthetic oils like Quaker State/ Pennzoil distributed by Shell in the US. Quaker state challenged Mobil last Spring which went unanswered so XOM accepts competitors are better at least in the 5W30 grade.

http://www.animegame.com/cars/Oil%20Tests.pdf


C4ZF6nut

WW7

Just for the record according to most engine builders motors should be broken in with dino oil, only after a few thousand miles should they be switched to synthetic oil.. I have heard many people claim there's no way synthetic oil can make your motor leak after running reg oil, but I have seen it happen many many times. I don't know if its because the synthetic oil cleans away the buildup in the older engine causing it to leak, or if the chemical makeup of synthetic causes it, but I have seen it happen too many times for it to be dismissed as an "Old Wives Tale".....WW

c4zf6nut

There is no benefit from a synthetic oil for our cars which have an oil cooler, and hardly stress the oil. Use synthetic if you need to operate at extreme low temperature (not wise in a Corvette).

People are just spoiled by the low price of oil in the US. I pay $10/quart for semi synthetic in Europe, and cannot afford the synthetic anyway. Spend your money on a good oil filter like Puralotor PureOne.

Use oils with high extreme pressure additives, Bob is the Oil Guy forums are valuable resource for your 86.

cadmaniac

I wouldn't do it. I would also agree to get the additive for flat tappet motors, and don't take that lightly!

You don't want to ruin an engine because the oil companies decided to remove it from the oil. Especially since it is such a pampered automobile!

hgh pwr

i don't think the oil company's removed the zinc and so on from their oil, it is for lower emissions that are being forced on all car manufactures.

Someone can retrofit the roller valve train for not a whole lot of money if they are worried about excess wear from the removal of zinc and phosporus.

cv67

Amsoil has a Zrod synthetic oil that seems to have higher levels of zinc/zddp than most out there.

Syn wont cause the motor to leak.

Weight for weight it does pour thinner than dino oil so it may find a potential leak quicker than the dino.

If the gaskets are old and shrunken anyway then..


Personally never noticed a difference in switching, never developed leaks because of it. Even ran it in a FT engine with no issues (Mobil1 10/30, hear the 15/50 is best for that too).

Bottom line is any oil out there is probably better than what was around in 86

Seadawg

There are WAY too many variables with different climate, different driving styles, even different types of vettes to say absolutely this is what EVERYONE should do,

It is never an apples to apples comparison in the real world. About the best we can do (if we really are worried about it, which none of us should be) is to test OUR oil at OUR change interval, by sending to a company like Blackstone labs, and then compare results over time.

As an example, I change mine between 7,500 to 10K miles, which is about 10 -15% on the DIC for oil life. As for driving style, I'm over 5K rpms literally EVERY day, 365 days a year, and now now have close to 100k miles on my 2011 GS.

About every 30k miles, I send s sample out for testing, and the results are almost identical every time. So I've now got 4 tests to compare. They all basically say my oil is "fine", and that I have well over 50% of all additives, etc. left in it, and I should go at least 15k miles between changes.

Will I do anything different? No, not until the test results show something different

This is with Mobil 1 5W30 and mostly Mobil 1 filters.

But AGAIN, I guarantee your test results will be different on your car

aklim

I changed to synthetic for most of the cars I have bought over the last 20 years (not beaters). A very good example is the Ford Powerstroke 7.3. Ford recommends a 15W40 oil be changed (15 qts) ever 3000. Switched the oil to 5W40 Rotella which is synthetic (or so it says), and the lab showed I could extend the change interval to 6000. Even if money wise it is a push, I save time on oil changes, dragging the oil somewhere to dump, cleaning up, etc.

cv67

Any difference after 7 yrs ? lol

aklim

Actually, no. Results from the test seem to hold steady

xrav22

At 180000 I am running Kendal GT-1 Synth for the first time. I wanted to monitor oil temps and see if any difference.
I have new seals and am extending my oil changes to 5000. Temps seem the same and I can't tell the difference yet.

aklim

What does the used oil analysis say would be more meaningful.

KyleF

Conventional oil and filters are much better in quality and purity today than they were 30 years ago.

I would venture to say most of us do not put the miles on a C4 to hit regular oil changes anyway. Some may still drive their cars this much, but most are not in current days. There are not a lot of advantages to going synthetic in a weekend cruiser. If you are racing or otherwise seeing "extreme" service conditions (High Heat, High RPM, sandy environments, and etc. ) then there are, but not for a cruiser.

Conventional Oil takes a long time to "Go Bad", it's not like gasoline. Shelf life is up to about 5 years IIRC. Synthetic is claimed to be basically infinite if stored properly. So, if you ever get a bang up deal on a pallet, you might want to stick to synthetic

The reason you are supposed to change the oil every season it not the oil itself. It is the build up of combustion byproducts that increase the acidity of the oil. This helps eat at seals, gaskets, and especially aluminum. To be honest I don't know how long it would take for oil that has a few thousand miles on it to actually cause damage, but when you consider the time and money to repair some leaks that can occur, it is easier to just change the oil before winter storage and not worry about it.

My winter prep is to drive the car to a near empty tank, add stabil and fill it up. Drive home gives it time to get through the fuel system. Change the oil, change the supercharger oil, air up the tires to near max PSI for the tire, and then drive the car up on some 1/2" thick wood plates. I then toss some rat poison under the car, put a couple of bags of marine desiccant indside, hook a battery tender up, and then cover him up and not worry about it. I have had a "fair weather" car for going on 8 years now. I have never had a problem with them being turn key ready the next season, aside from usually needing to add air to the tires. Take it easy until the take of old gas is used up.

toddbvanslyke

It's fine. Switch back and forth all you want. Most negatives about synth are myths anyway: they're not too slippery, they won't cause bearings to spin or any of that nonsense. And they don't seek out leaks but, in truth might cause leaks by cleaning crud off seals and gaskets that's been baked on with dino oil. With a well-maintained motor, shouldn't be an issue one way or another. I've used straight synthetic in all sorts of cars since the '80s... 1940 Packard, 1957 BelAir, 1959 Thunderbird, 1967 Excalibur... plus all my Harley motorcycles with nary a hitch. Now my 88 Corvette, 2012 Liberty, and 2018 Grand Cherokee run exclusively on 100% synthetic.

84 4+3

Holy grave digging threads batman!