Ok, with that to a certain extent, but before replying to your post, I did a quick advanced search to see what the search engine brought up, and this is the response I got.
http://forums.corvetteforum.com/search.php?do=process

I understand your frustration, but when you are looking for something, and this is what it comes up with in response, sometimes its just easier to ask then spend 2 hours searching.
The search is not like it used to be......trust me, I know.

Laura

Foot note, when I typed in oil for a 1996, I got a page full of subjects about oil, but when I just clicked on the link I posted, it didnt show that. Sorry about that.

 

its an old gen II engine. put any old 5-10/w oil in it and change it every 5k miles.

no worries.

 

40% amsoil 10w30 40% royal purple 0w30 and 20% lucas oil stabalizer.
Just get mobile 1 synthetic in whatever weight is on the oil cap.

 

Not sure if this would apply to a C-4 or not, but after the oils were reformulated in 07 to meet the new EPA standards and after a lot of reading, I switch to “Mobil One High Mileage” in my Chevelle. It’s supposed to have more friction additives in it that are now lacking in the new formula oils. And from what I have read it’s better for flat tappet cam engines that needed the higher Zink levels of the old oils. It also contains seal conditioners that help with oil seepage in high mile engines. It only comes in 10-30 or 10-40 so don’t know how if it would work in a high mile Corvette but I would think 5-30 would be a little thin with old high mileage seals. Anyway it’s a full synthetic oil and has worked fine in the Chevelle so far.

 

Thank you very much!

 

I feel that this is common misunderstanding. A 5w30 isn't by definition any "thinner" than a 10w30. An oil's hot viscosity is rated at a temperature of 100C (212F). 30 grade oils, the second number in a multi-visocisty oil's rating, must have a cSt viscosity of 9.30-12.49 at 100C. A 0w30, 5w30, 10w30 and even a straight grade SAE 30 all have a hot viscosity in this same range, so one isn't any "thinner" or "thicker" than another.

The first number in a multi-vicosity oils rating refers to its cold, or winter viscosity. This viscosity is measured at 40C (100F), so it really isn't that cold. The lower number tends to confuse some. The oil is actually much much "thicker" when cold. However, the difference between a 0w30, 5w30 and 10w30 isn't as much as most think at the relatively warm temp of 100F. For example, the AMSOIL Signature Series 0w30 has a 100F viscosity of 56.6 cSt, the AMSOIL SAE Synthetic 5w30 has a 100F viscosity of 59 cSt, and the AMSOIL SAE 10w30 has a 100F viscosity of 62 cSt. Note that all of these are about 5-6 times higher than the 30 grade's hot oil viscosity of 9.30-12.49 cSt.

Thus when hot, a 10w30 isn't by definition any thinner than a 5w30, and when cold it is much much thicker than either a 5w30 or 10w30 is when hot, so again the perception that it is "thinner" isn't really applicable.

All that said, the oil's impact on older seals is more a result of its basestock that its viscosity. Group III synthetics, the majority on the market, use a highly processed mineral oil basestock and their impact on seals is essentially the same as any old mineral oil. Group IV synthetic oils, such as AMSOIL's SAE and Signature Series lines and probably Mobil 1, use a PAO basestock. The PAO basestock causes seals to shrink. Group V synthetic basestock, such as the polyol ester used by Red Line, tend to swell seals. But, by blending small percentages of esters to their predominantly PAO basestock, companies like AMSOIL can create a fluid that causes seals to very slightly swell.

Another common factor to seal leakage is that most synthetics use higher levels of detergents than are used in mineral oils. The detergent cleans sludge that can expose oil dried out seals to the synthetic fluid and may result in leaks. Depending on the basestock, and the damaged caused by drying to the seals, these leaks may seal up, or they may persist.

 

 

Just want to add a few points.

Oil is not multi-viscosity. A viscosity range is obtained by additives. More range means more additives that can degrade and burn off. That is one cause of oil volume loss and when the additives fail from high temps or use over time, you are left with oil at the low number of the range. Our Volvo overheated and the oil became so thin, the oil pressure light came on. Replaced water pump and oil and all was well -- you really had to love the old Volvos.

MPG was a major consideration when GM specified the oil range. Likewise, running a "hot" engine was about emissions and MPG. The engine is perfectly happy with 20-40 running at 190, but MPG is negatively affected. (Emissions might increase but my car passed in CA running at about 190.)

If you want to go faster in the quarter, drop temperature, drop oil weight, and reduce the oil volume as much as you can. Say 4 qts of 10-20? If you want maximum MPG, NASCAR or GM fleet standards for example, run as thin an oil as you can and run as hot as you can (e.g., OEM specs).

If you don't care much about MPG or emissions or maximum performance but want to run forever, drop temperature, use the highest base weight you can in your climate, and keep the sulfur -- say a 20-40 diesel oil spec for most of us.

Mobil 1 is on the oil fill cap because Mobil Oil paid GM to put it there.

Please don't fall for the idea that moisture will not burn off unless the oil temperature exceeds 212. If that were true, rain puddles would never evaporate. It does happen faster at higher temps but it happens at any temperature above freezing. I did have a moisture problem with a 2 mile commute during winter with a motorcycle that had an oil cooler and no thermostat. In a car with a thermostat, the 2 mile commute was no problem. Wish I still had a two mile commute.

 

Overall, agree with your points with the minor exception that many modern synthetics are multi-viscosity to an extent not true of mineral based oils. Many AMSOIL products achieve a multi-viscosity rating without the use of viscosity improvers.

 

MOBILE 1

 

I'm a lifelong Castrol guy so I put Syntec in all my vehicles. But Mobil 1 is just as good.

I don't trust Pennzoil or most of the others, unless I'm stuck in the desert hundreds of miles from civilization and all they've got is something like single-weight Havoline 30. Pour it in, get out of there and change soon.

 

I ONLY use single weight Havoline 30 in all of my engines...$1.49/QT by the case baby

 

I started using Amsoil 10W-30 in my Dodge Ram at 2500 miles with no problems. I switched to Mobil1 10W-30 at 15,000 miles and I started to loose (burn ?) 1 quart of oil every 3-4000 miles. I switched back (after 2 oil changes) to Amsoil and have not lost a drop yet. I called Mobil and asked them if I went to 10W-40 would that help prevent my oil usage? Mobil said I was within the allowable usage rate and they would not recommend anything other than the mfg recommended oil weight.
I use Valvoline Synpower in my 92 and 79, I usually stock up when Walmart rolls back its price or discounts it out when Valvoline changes the labels on the the bottles. When I used Mobil1 in my 92 I was always wiping up my garage floor.... That's my story.