Hey, I remember that thread Venom mentioned! It'* also that it leaves thicker deposits on the bottom of the oil pan after a while. Those won't drain out of there with our oil pan design.

I think somewhere in the manual for this car it calls for mobile 1 synthetic don't quote me on that I'm not 100% sure but I thought I read it somewhere in there

Not a page in it says a word on synthetic. You can get the "Mobil 1 5W 30 Synthetic" oil cap from a Corvette and put it on your valve cover, though.

I meant like it ask for mobile 1

OK on the refresher course, but wouldn't that mean once rico'* 0w30 oil would perform like 5w30 or 10w30, regardless once reaching full operation temp?

I always did an engine flush also with changes, was told to be careful on older engines as sludge holds things together at times.

So how does the viscosity scale work? Is the lower the number thicker and the higher number thinner? And what are the lowest and highest ratings? Anybody out there know that information?

I use Mobil 1 10w-30 in the Summer (avg. temp is in 90'*) and Mobil 1 10w-40 in the Winter (60'* -70'*). Does that sound about right?

The viscosity of oil is based on the blend of polymers within the oil. Viscosity is graded by measuring the time it takes for a standard amount of oil to flow through a standard orifice, at standard temperature. The longer it takes, the higher the viscosity, and thus higher SAE code.Those temperature ranges are from 0F to normal operating temperature which is around 190 to 210F. The higher the number, the thicker the oil (more polymers) at those temperatures.

If you use a 10w30 in summer and a 10w40 in winter, you are really not gaining any better protection. Stick to what the manufacturer of your vehicle recommends.

The viscosity of multi-weight motor oil is specified using two numbers. The first number is the viscosity when the oil is cold. This is followed by the letter W (which stands for winter, not weight), which is followed by the number that indicates the viscosity when the oil is at operating temperature. The higher the number the thicker the oil.

Using 10w40 in the winter doesnt help anything. It makes for thicker oil. The second number is when oil is hot. And the engine is the same temperature when warmed up, summer or winter. 10w30 is fine all year. Changing oil weights seasonally is a hold over from when oil only had one weight, before the discovery of the polymers that allow for multi weight oils.

Car makers went to 5w30 because engine part clearances have become less in recent years. When newer made engines start cold, 10w30 can cause oil interference. It is best to use what is recommended, The car maker matches the numbers to the clearances of the engine.

I have heard many times of engine flushes creating leaks in older engines. I suppose the solvents that clean can also soften older gaskets and further cracks that have already started. Keep your engine clean with regular oil/filter changes and you wont need them.

As for Ricos case. Worn lifters start ticking at the ultra thin level, and they are stubborn to make stop, dont know as to exactly why. Just that they are like that.

Add on question about oil for Northstars ...

Always used Mobil 1 in the SSEi but the GXP (had about 6 months) seems to leak onto manifold on hard braking. Speed shop guy said his buddy has Northstar and said they leak so he runs conventional.

Is there any common knowledge on Northstars leaking, etc.

I really am not ready to open cam covers. Besides, you can barely get your fingers down front of engine.

PonchoPete
2005 Bonneville GXP – Dk Grey
2001 Grand Prix GTP
1994 Bonneville SSEi – * Port Magnuson SC
1969 Grand Prix SJ – 428cid/370hp

Old pre 2002 I believe N*'* were leakers. They got better at casting aluminum since. I dumped the OEM oil after a hard first 1000 miles when mine was new, and have run only Mobil 1 and Syntec since, never had a leak. She liked to blow oil through the rings at first. But they finally seated well. These N*'* have to be excersised well to break them in. Some members have reported oil line leaks at the fitting. I'm one of the lucky ones I guess.